Citation
Geographic variation in slash pine (Pinus elliottii Engelm.)

Material Information

Title:
Geographic variation in slash pine (Pinus elliottii Engelm.)
Creator:
Squillace, Anthony E., 1915- ( Dissertant )
Wallace, A. T. ( Thesis advisor )
Ash, William O. ( Reviewer )
Conger, A. D. ( Reviewer )
Goddard, R. E. ( Reviewer )
Kaufman, C. M. ( Reviewer )
Noggle, G. R. ( Reviewer )
Place of Publication:
Gainesville, Fla.
Publisher:
University of Florida
Publication Date:
Copyright Date:
1964
Language:
English
Physical Description:
vii, 181 leaves : ill. ; 28 cm.

Subjects

Subjects / Keywords:
Forest trees ( jstor )
Forests ( jstor )
Germination ( jstor )
Phenotypic traits ( jstor )
Pine trees ( jstor )
Seed trees ( jstor )
Seedlings ( jstor )
Species ( jstor )
Stomata ( jstor )
Trees ( jstor )
Botany thesis Ph. D
Dissertations, Academic -- Botany -- UF
Plants -- Variation ( lcsh )
Slash pine ( lcsh )
Miami metropolitan area ( local )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Abstract:
When a plant species occurs over a wide geographic range, individuals or populations growing in different localities frequently display differences in one or more traits. This phenotypic variation associated with locality (geographic variation) may he due to environmental or genetic factors, or interactions between them. Environmental differences are a consequence of modifications caused by habitat factors. Genetic variation associated with locality (racial variation), on the other hand, is due to such mechanisms as mutation, natural selection, hybridization, or combinations of these factors. It basically results from the fact that the individuals within populations differ genetically. The genetic heterogeneity between individuals is caused by mutation or hybridization. It is maintained by Intricate mechanisms inherent in most species, enhancing chances of survival of the species in a constantly changing environment. This genetic variation among individuals is the basis for racial variation. If the localities are characterized by different environments, and if some degree of reproductive isolation is present, racial variation will occur. Plants that are genetically most suited to their particular habitat will survive and reproduce In greater numbers than those not so well endowed. Some degree of reproductive isolation is necessary because If interbreeding occurs randomly throughout a species range, natural selection in a given locality would merely result in a change in the mean of the whole species. In forest trees, sufficient isolation is provided by the limited distance of pollen and seed dispersal. Although natural selection Is the most Important cause of racial variation, it is believed that such variation nay also result from chance fluctuations in gene frequencies (genetic drift) leading to fixation of genes. Genetic drift is most apt to occur in small, isolated populations and environmental differences need not he present. Geographic variation occurs in characteristic patterns, depending upon the nature of the forces that caused it. Since climatic factors are often important natural selection forces, and since climate often changes gradually over a species range, the pattern of racial variation frequently is continuous or clinal. However, relatively uniform and discontinuous habitats may cause relatively discrete populations or ecotypes. Likewise, present or past Isolation may cause ecotypes or combinations of both clinal and ecotypic variation. Needless to say, geographic variation In forest trees is common, and it is of great interest to forest land managers and forest scientists. The nature of geographic variation (i.e., the proportion of environmental and genetic components) is important to land managers because if differences in economically important traits are genetic they must use care in selecting sources of seed for forest planting. Likewise, forest geneticists are keenly aware of the possibilities of capitalizing on racial variation in development of superior strains. Taxonomists are interested in patterns of variation in their attempts to classify trees on both the species and subspecies level. The present study was designed mainly to Investigate the nature and patterns of geographic and racial variation for a number of characteristics in slash pine (Pinus elliottii Engelm.), one of the more important commercial trees of the Southeast. Secondary objectives were (l) to search for causes of patterns of variation that sight he found, and (2) to compare the magnitude of variation associated with localities against that associated with individuals within localities.
Thesis:
Thesis (Ph. D.)--University of Florida, 1964.
Bibliography:
Includes bibliographical references (leaves 122-129).
General Note:
Vita.
Statement of Responsibility:
by Anthony E. Squillace.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright [name of dissertation author]. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
030022202 ( AlephBibNum )
ACG4741 ( NOTIS )
08374529 ( OCLC )

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GEOGRAPHIC VARIATION IN SLASH PINE

(Pinus elliottii Engelm.)











By
ANTHONY E. SQUILLACE


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY












UNIVERSITY OF FLORIDA


April, 1964











ACM,-OWLEDGEDMENTS


The author gratefully acknowledges the assistance of his

supervisory committee: Drs. A. T. Wallace (Chairman), W. O.Ash,

A. D. Conger, R. E. Goddard, C. M. Kaufman, and G. R. Nocgle.

Special gratitude is also due the following organizations for

assistance in collecting seed and foliar samples used in the study:

Buckeye Cellulose Corporation, Foley, Florida; Continental Can

Company, Incorporated, Savannah, Georgia; Florida Forest Service;

Georgia Forestry Commission; International Paper Company, Bainbridge,

Georgia; School of Forestry, University of Florida; South Carolina

Commission of Forestry; West Virginia Pulp and Paper Corporation,

Georgetown, South Carolina.

Statistical computations were done at the University of

Florida Canputing Center and financed jointly by that unit, the

School of Forestry of the University, and the Southeastern Forest

Experiment Station. The author is Grateful to these orCanizations

and to personnel who helped with the work. In this effort,

special thanks are due Ir. John C. Barnes who did most of the

proLramning and Dr. A. E. Brandt for statistical counseling.

Finally, the author is very grateful to the Southeastern

Forest Experiment Station for providing facilities, materials,

and technical help and to the many persons of the Olustee Uaval

Stores and Timber Production Laboratory who helped in various

ways on the project.









TALU OF CUMO

Page

LIST OF TABLM . .... ...... ............ iv

LIST OF FInFW ............. ............ v

IQnU erTUl ... .. .. .... ........ 1

IVIVW OP LnUTtJ ....... ............ 4
81uBhn P . . .... . ..... .. .. . .. .. 8


BASIS FO YTAIATIOK IN KAU PIB . . . . . . . . 15

PMrogm tera . . . . . . . . .. . . 2
PaantalNet a........................... 24

Single rate analys ........ . .. ... 29

tivariate analysis . . . . . . . . . 35
5RWMB yAeNldU .. . . . . . . . . . . .. 37
Sgle ariMte Anale *...................... 37

ene dimens nss...... ............. 37
e ielt .......... l. . . . . .... . 3
SeeB A.b dimaiOa . . . . . . . ..... 37
Sl eed Y.Led* A. L. . a a a a a . a a a * * 37


GerSiudility and s ed of gft intion . . . . . 46
Getyledemin ber . . . . .. . . . . . 54
Total height . . . . . . . . . 56
St d e r .... . . ... .. . ...... 63
Needlesper faile . . . . .. .. . . 68
Deirlength ................ ....... 72


suffer of resin ducts ... .... ......... 85
ThldKnee ef h peB ...... .............


Mltivawlnae Analys ... . . . . . . . 106
NDvecaitury Amh ndirtions Within Sta nd .. * *. 117
DivTAsity cmogie s . . . . . . . . . 119
MultiveriteAnalysis.................... 106
Nomenclatural Gansihdrations ................. -17

SUMMY AIM CdMMIOM.....................0 0 0 0 0 0 0 0 0 0 0 119

LIMIAIM CITED . . ...... . . . . . . . 122

A . . . . . . . . ...... 130

iii








LIST OF TABLES

Table Page

1. Sumary of slash pine seed source tests which
sampled a relatively narrow latitudinal zone . . . .. 11

2. Summary of slash pine seed source tests which
sampled a relatively wide latitudinal zone . . . .. 12

3. Means and ranges of variation for parental data . . . .38

4. Mean squares and estimates of variance components
obtained from analyses of variance of parent tree data . 39

5. Means and ranges of variation for progeny data of
Nursery Test 2 . . . . . . . . . . . 47

6. Mean squares and estimates of variance components
obtained from analyses of variance of progeny
data of Nursery Test 2 .................. .48

7. Means and ranges of variation for progeny data of
Nursery Test 1 . . . . . . . . . . . 57

8. Mean squares and estimates of variance components
obtained from analyses of variance of progeny
data of Nursery Test 1 ......... ...... 58

9. Coefficients of variation for parental data--per cent . . 99

10. Coefficients of variation for progeny data of
Nursery Test 1--per cent . . . . . . ... 100

11. Coefficients of variation for progeny data of
Nursery Test 2--per cent . .... ...... .. . 101

12. D values (x 10), with stands arranged in order of
decreasing similarity to 8 stands in the north-central
region .. . . . . . . . . . . . .. 107

13. Average within- and between-cluster D values (x 10),
clusters formed as described in text and arranged in
order of decreasing similarity to "North-central
(west)" cluster . . . . . . . .... ..... 111

14. D values (x 10) for stands in a transect going from
stand 24 (north-central region) southward through
the center of Florida to stand 47 (south Florida) . . .. 116








LIST 0' FIfUM

Firire Page

1. Ranges of the two varieties *f slash pinE ad
locatil sf otf t lan... led . . . . . . 9

2. Z JIn y teqr tn ................. 16

3. Averg diffeumee between mu mudiw ad owM
indamr towmeratue (Or.) during athsl of April
thtre'h gtember. .. ................. 17

4. MMm amuel preeipitatiE .* . . . . * . 19

5. Preciydtatle from etsbesr %waeieh M -a pe r aet
of Sma mmal pleiitAribi. 0 0 . . . . . 20

6. TheM s ef precipitatia-ovgeortie ratios for
mths el Fbruay tlughe April. ... ... . .. .. 22

7. em patem of stadL veriatioa in teae length .* . . . 40

8. The pttera of stant vyriatiLe in er s a m err. .. .. . 41

9. The ptter of st ad variation in soad n sa yield
par OGe. a * a . a a * * * 44

10. ihe pattern o stand variation in seed night. . . . * 45

11. Te pttehrn of stead variation in s-e od dmability. . 49

12. The pattern of stead aristion in sped of se*a


13. The patter of stat ve atien in nue of
otyLeasi p er sNdling. . . ............ 55

14. The pattern of riat variatlia in heights at
needlias.................... ..... 59

15. On-yer-eld slsh pine seedlings, showing
diffrencs in total height and stm dimtr. . . . 61

16. Th pattern of sat variat ion in state dwieter. . . . 6

17. The pattern of stai variatiU in wrongs nuber
of o edles per facile in parest trees. . . . . 69










LIST OF FIGUtSB (continmd)


Figure

18. The pattern of stand variation in average number
of needles per fascicle in progenies.. .* * * *

19. Th pattern of stand variation in needle length
in parent trees. ... . . . . . ** *

20. The pattern of stand variation in needle length
in progenies. . . .. . . * . . **

21. The pattern of stand variation in fascicle sheath
length in parents. ....... *. * * *

22. The pattern of stand variation in fascicle sheath
length in progenie.. . . . . * . .

23. The pattern of stand variation in number of
rows of stomata per a. of needle width in
parents* e e e e e e * * * * * * * * *

24. The pattern of stand variation in number of rows
of staata per m. of needle width in progeniee. . .


25. The pattern of stand
stoeta per m. of

26. The pattern of stead
stmata per m. of


variation in number of
needle length in parent.

variationea number of
needle length in progenies.


*. 0


. . .


27. The pattern of stand variation in number of
smatat per sq. m. of needle surface in parents.

26. Th pattern of stand variation in number of
stoata per sq. m. of needle surface in pregenies.

29. The pattern of staad variation in number of
resin ducts per needle in parents. .......

30. The pattern of stand variation in ntuber of
resin ducts per needle in progenies. . . . .

31. The pattern of stead variation in number of
layers of hypoderm in parents. . . . ....

32. The pattern of stand variation in number of
layers of hypedier in progenies. ........

vi


Page


. .


. .


. .


. .


. .


. .








LIST Or FIG0W (testiand)


Figure Pag

33. Average of 3 valY e between each s4kad at eight
stwema within the Mnrth-central regiai, awing
the egree of similarity that regie.. . . . . 109

3k. Delimeatio of clusters of stols for ie in
determinga relative ips. . . . . . . . . 113

35. agrawatic rpreentation of the appey iuate
degree f similarity mes clusters of *stas
aeeording to average between-cluster D valws. . . . 114


vii










When a plant species occurs over a vide geographic range,

individuals or populations growing in different localities frequently

display differences in one or mere traits. This phenotypie variation

associated with locality geographice varition) me be dme to eviren-

mantal or genetic factors, or interaction between thee.

lnviroamntal difference are a consequence of modifications

caused by habitat factors. Genetic variation associated vith locality

(racial variation), on the other hand, is due to such meahenism as

mutation, natural selection, hybridization, or combinations of these

factors. It bsieally results from the fact that the individuals

within populations differ genetically. The genetic heterogeneity

between individuals is caused by rtatioa or hybridization. It is

maintained by intricate macha-ims inherent in mest species, enhancing

chances of survival of the species in a constantly changing envireimat.

This genetic variation meng individuals is the basis for racial

variation.

If the localities are characterized by different envirommats,

and if sem degree of reproductive isolation is presents racial

variation will occur. Pleats that are genetically mest suited to

their particular habitat will wsrvive and reproduce in greater aubers

than these not so well ended. Sea degree of reproductive isolation

is necessary because if interbreeding occurs readely throughout a

species range, natural selection in a given locality would merely

result in a change in the men of the whole species. In forest trees,

sufficient isolation is provided by the limited distance of pollen and
seed dispersal.






2

Although natural sMlectia is the mat iwpertat meme of racial

variatie, it is belleed that umh variatiom my als result fro

chme. fluetwttoms in gwe frequo cies (emetic drift) losing to

fixatsxe of umes. Gretie drift is most pt to occur in mall,

isolated populaties ard oevirie-mei diffiraees ee aot be prreet.

(IG gr* aic variation oceurs in ckeracteristic pattern, depeding

upo the asture of the ferees that eamed it. Siae climatic factors

are eftm important natural seaetion forces, aft smine climate eftb

eh. Ms Cgratlly ever a species rage, the pattern of racial variation

frequently is oestinuous or elial. However, relatively uiform and

diasntinwuas hkbitatA mW cause relatively disfeete pepulatia s or

eeetypes. Likewise, prosnt or past iseatioe ay ease ecotypes or

acembitioAn of beth clinal d eeotypic variation.

Needles to ay, pogriphbic variation in foest trees is coma,

at it is of great interest to forest lad -age ad forest

setemtists. 'E aeture of geographic variation (i.e., the proportion

of evrommiter l ma agnetic cmpoments) is lpeortet to lad Masaers

beease if differences in eseamielly importat tracts are genetic

they met we eare in seaeeting srrees of se m for fewest plating.

Likeowse, forget otisists ae keenly Mwee o tie peesibilities

of espitalising en reial vTariateu in deveely-nt at se erior strains.

Tamommists m interest* in patterns of variatite in their attempts

to classify trees a both the species ad sur species level.

The present study was dsign*d mainly to investigte the nature

ad patt eus of geographie ad racial variatieo for a nWber of

chareoteristios in slash pine (Pinus elliettii enela.), me of the








3
more important commercial trees of the Southeast. Secondary objectives

were (1) to search for causes f patterns of variation that might be

found, and (2) to cpware the magnitude of variation associated with

localities against that associated with individuals within localities.








REVIEW OF LITERATURE

General

It is probably safe to say that geographic variation has been

studied in all commercially important forest tree species and in

many of the noncomnercially important ones. Langlet (1938)

summarized much of the early work. Several recent publications

include brief reviews of much of the past literature: Dorman (1952),

Critchfield (1957), Echols (1958), Squillace and Bincham (1958),

Callaham (1962), and Langlet (1953).

These studies have demonstrated that racial variation is

prevalent in forest trees, although some species such as red pine

(P. resinosa Ait.) chowed no, or relatively small, variation in

some traits (Buchnan and Buchman, 1962; and Wright et al., 1963).

As might be expected, differences were found to be Greatest, or

most prevalent, where the species range covered a large geoGraphic

area, such as ponderosa pine (P. ponderosa Lais.) and Scotch pine

(P. sylvestris L.). Uowvver, variation has been found even in

trees having a relatively small geographic range, such as sand pine

(P. clausa (Chapm.) Vasey)(Little and Dorman, 1952a), and western

white pine (P. nonticola Dougl.) (Squillace and Binjlam, 1958).








Mny of the patterns reported contained an elent of continuous

or clinal variation. Where the variation is a result of gradual

changes in climatic or geograhic features, and where complete repro-

ductive isolation is absent, one might, of course, expect the variation

in plant characteristics to be continuous. Stebbins (1950, p. 44)

expressed the opinion that most species with a continuous range,

enco~assing changes in latitude or cliaate, will be found to possess

lines for physiological characteristics adapting the to conditions

prevailing in various parts of their range. NHerous patterns showing

continuous variation associated with rainfall have been reported

(Larson, 1957; Thorbjornsen, 1961; Goddard nd Stricklad, 1962; aad

Squillace ad Silen, 1962). Blevational trends were reported by

Callahan and Liddicoet (1961) end Critchfield (1957). N* erus

istances of gradual changes associated with latitude or length of

photoperiod hxve been found (Latglet, 1936; and Schoenike ad Brevn,

1963).

One frequently also see in the literature evidences of ecotypic

patterns of variation (for exples, see Wright, 1944; Pauley and

Perry, 1954; Vaertaja, 1954; Squillace ad Binghm, 1958; ad Wells,

1962). However, same of these anthers used the term broadly, applying

it to patterns which re genetic ad atWptive but not neceserily

discontinuous. Too, there is often sem question as to whether the

ecotypic variation occurs exclusive of other types.









Theoretically, distinct ecotypes with no element of

continuity can occur in a species having geographical isolation,

and in which genetic adaptation to a uniform habitat (such as soil

or exposure) has occurred. However, since the habitat within a

species range or within parts of a species range often varies

continuously, combinations of patterns are more likely. Thus, it

is possible to visualize a situation in which a species occurs in

geographically isolated groups, with ecotypic variation occurring

among groups as a result of adaptation or genetic drift, or both.

But with the climate varying continuously through the range we

could have clinal variation occurring both within and between the

ecotypes. This may indeed be the situation in snme species such as

ponderosa pine, in which elevational gradients were reported by

Callahan and Liddicoet (1961), and in which ecotypes were

delineated by Wells (1962). In this same species, Squillace and

Silen (1962) pointed out apparent clinal variation associated with

climatic variables but acknowlveded that likelihood that

discontinuities also occurred; irregularities in a clinal pattern

were illustrated by Callahan and Hasel (1961). Clausen et al.

(1948) found clinal trends for height of plant between climatic

races of Achillea lanulosa. In Scotch pine, Wright and Baldwin

(1957) and Wright and Bull (1963) delineated broad ecotypes within

the species range, hlile Langlet (1936) pointed out that clinal

variation for certain characteristics occur both within and

between ecotypes of this species.









The existence or nonexistence of the two 1-inds of variation

often becomes a matter of degree, with interpretation highly

subject to the opinions of the investigator and confused by

terminology. It is no wonder that considerable discussion and

debate have resulted on this problem (Turesson, 1936; Faegri,

1937; Langlet, 1936, 1959, and 1963; Kriebel, 1956; and Callahan,

1962). Until more concrete terminology and guidelines for

classification are available (if indeed ever) the wise investigator

will describe his pattern of variation as best he can without

attempting to classify it categorically (Langlet, 1963).

Another type of variation noted rather frequently in the

literature is random variation. Here differences among stands

sampled within the species range may be real but exhibit no

distinctive Gcographical trends or patterns such as lines or

ecotypes. This type of variation is likely to occur where the

species range is discontinuous in the present or had been so at

some time in the recent past, as exemplified by the random pattern

found in the major portion of the range of European black pine (Pinus

nicra Arnold) by Urigit and Bull (1962). However, random differences

have been found for seed Cermination in slash pine by Hergen and

Iloelstra (1954). Likewise, Thorbjornsen (1961) reported random

variation for ving length, seed length, cone length, needle length,

and frequency of serrations on needle margins in loblolly pine (P.

taeda L.). Both of these species have rather continuous ranges.

The cause of random variations in such cases is obscure, although

partial reproductive isolation which is believed to be coamon in
most trees may have a bearing (Wright, 1943).








Slaws Pine

Slash pine, like m y pine species, has suffered a oacfused

neemnclature (Little a d baeam, 1954). Recently, these authors (1952b)

subdivided it into two varieties, P. elliettii angel var. elliottii,

typioel slash pine, and P. elliottii var. d4Mee Little ad Bormsn, South

Florida slamh pine, formally publishing a deseription of the latter.

The range of the two vrietles, as given by Little and Bonn

(1954), are shown in Figure 1. The authors showed the varieties as

being allopetric, the boundary between them being indieaed by the heavy

dashed line in central Florida. At a later date, Lagden (1963) published

a revised rage of the dean variety, extending it northward a considerable

distance a shown by the dotted line in Figure 1. He indicated that

trees of both varieties occur in the arma of overap. lash pine dees

not extend into the Caribben Islids.

Peatwes which, according to Little and IDoma (195k), distinguish

the two varieties are as follows:

Var. elliottii: Needles in fascicles of two and three, ad on ml

seedlings with erect, slender, pencillike stems.

Var. dena~ Needles in faseicles of two (infrequntly three);

seedling with grasslike, alaost steless stage with nry crowded needles,

and thick tap root. The vood of this variety is also heavier ad has

thicker o utnrood than the typieel variety.

Mature trees of the two varieties also differ srawwhat in general

ppiermee. Variety densa is norally shorter, with its stem often

foeuing into large branches sad its crown being generally flat-topped

at open, cared to the ui aly taller and relatively narrow-crwned

typical variety. However, according to mny foresters, these differeaese





































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ad ev the more Arttisettive sedling ehwaaeteristies beeme obscure

in the portions of the species rage whre the two varieties mt,

making it difficult or impossible to separae the tw vaTrieties.

lash pin*, being elatlvely sweeptible to fire inawy, was

originally caflined to pomns, ped orgias, mrl ether wrt aem

(Ceeper, 1957). With te avedet of white ma md fire protection it

hMa inaAed drier arems, whee it grows ?yatrielly with the relatively

fire resistant laongeL a pin (P. pal trlA Ml1.).

Seoth Florida slash pine oeeur in pue stads an flatweeds si es

in the southern part of its rage, while to the mort it is eofimet

to the wetter sites along stroms an in other porly drained or mwqy

area (Lemg9on, 1963). In the sMothern portie of its re there is

nm degree of geogrrepic ie latim betwom the two seestel ees,

eaMse by the 1verglades. The tw "preFes" along the eeest, however,

met in Polk a seeemla Seittee.

A nmber of seed suree studies studiess in which seeds were

selleeted f tress growing in different portion~ of the species ra~ e

sar plante in a s eem eavimmatt) have ben emdateted with slash

pine. Saom of these ampled only the eorther portiae of the species

rage (Tble 1), thile others namlet a relatively breed latitudinal

moe (Table 2). The studies were resigned minly to deteemine variatim

within the rage of *eliettli ealy. Newer, smling in some studies

of the latter greW (Table 2) eKtnled as far south s P rlk Ceosty,

Florida, wvteh is in the area brdert th tm varieties (treittioa

meo). In the "Fleridoe-a ergla" experiment (Table 2), a sinle mree

fell within the rage ef dmes (Collier Cesty, Florida) wv included











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2C 4-e -' 0 * '- O O O




*r 0 -A



(D -P r
\ o 3 'd
o 4 -



4 d 0 0C A 0

+ G\ \ G a



0 J 0\ 0 0
0C to I..






0 ,d to LO ccL
O I r- 0 H -H
U ) O
*i < c1 0 r S *




0 v 5(12 ri 0






O 0 H t U- 7N -

E-1 4 4) O O O 0
SH H : H CM E
0i h (1 H




O H C)




0 H ^i 0 / g 0
H 0 0 0 H
OU H COP
H i r4' 4' 3 5- ,.






13

along with elliottii sources in cne of the seven plantations in the test,

but was not included in the statistical tests indicated.

As seen in Tables 1 and 2, significant differences were found more

frequently in those studies sampling a bread latitudinal zone than in

those sapling only the northern part of the species range. This was

especially true for growth rate. In one experiment, latitudinal growth

rate differences were mainly due to a sample from Polk County, Florida,

in the transition zone and results suggested the existence of natural

hybridization between varieties in that area (Mergcn, 1954; and

Wakeley, 1959). (For further evidences of hybridization see Mergen, 1958.)

In still another experiment, Growth rate was usually moderately superior

among sources from extreme south Georgia and north Florida ( north-central

region ), and it decreased both to the north and south ef this area

(Squillace and Kraus, 1959). These authors suggested that climatic

conditions may be optimum in the north-central region, where superior

growth rate mlay have resulted from relatively strong natural selection

for this trait. Resistance to cold damage in the northern fringe and

unfavorable distribution of rainfall in he southern areas may have

been relatively more important than growth rate in natural selection

in these areas.

The results for survival were similar to those for growth rate--

differences were found more frequently when a broad latitudinal zone

was sampled than when only the northern portion of the species range

was sampled. In both the "Southwide" and the "Florida-Georgia" studies

early survival was usually greater among northern sources than among

southern ones. Some traits, such as stomatal frequency (Mergen, 1958)







ad fusifem rust resoistmee (Henry, 1959), shaed evidenees of

loagltudiaal variaion in the nerth.

several studies other than seed esore tests, hae also provided

information on go gaphic varition in slash pine. A plutatiu user

Gstameville, Florids, coeabSing cloea from phemtypically superior

trees selected in vaeris pertious o the ra ge of elliottli (eTrry

and Vang, 1955) osowe diffieemes ia Sm yielding ability at ahoat

7 yeas of ae (Anowamous, 1962, p. 124). A eaktle &im test in

south Florida, cqparing the two varietUes ef ssh pine, showed

siiafient differemesa in grpeth at survival (Hilum, et al., 1962).

Stemsod specific cavity ma/or smerrood per ceot wre studied in

elliottii tres grwiag in their nmbtral abitatu by several investigators

(Larsom, 1957; Perry and Was, 1958; Wheeler Mlat itehell, 1959 md 1962;

and Geaderd at stricklmd, 196). These studies aread in showing that

specific gravity ad samrweued per ceat increase in gling frm north

to senth through Georgia ad Florida, md fro wet to east through the

northern portion of the species rage. Ike elinal pattern of variatiOb

was shown to be closely associated with seaemal distribution of rainfall,

in admitiae to latitiw au d leegitde. ewever, the two experiaJts

reported 1oa1 by Ecuels (1960), sham in Table 1, acsg t that the

pattern in these weod properties is largely eviremmtal rather tha

gantic. Variation in tim ef poll. ad msed ripeidg bha been

reported by BomsI ad aerer (1956).

As neotd srlier, the Soe stacties de6 t minly with variety

elliottli. The possibility of variation within variety deA~i mr

to have eseeed rtudy.








BASIS FOM VARIATION IN SLASH PIE

This section contains an examination of the environmental

factors thich ay have been instrumental in causing geogr qhic and/or

racial variation to be reported. Information on climate was freely

drawn from U.S. Weather Bureau reports (Weather Bureeu, 1956 and 1959).

Climate within the range of slash pine varies from a eone of

transition between taperate and subtropical conditions in the north to

tropical conditions in the Florida Keys. Taerature variation and

other factors are strongly affected by latitude and proximity to the

Atlantic Ocean or Gulf of NIxice. Smers ore relatively long, wamn,

and humid; winter are relatively mild due to the sextherly latitude

and vra adjacent sea waters, but periodically cool and cold air from

the north invades the region.

Mean January temperatures increase gradually from a lov of about

50F. at the northern extreme in South Carolina to a high of about 70o?.

in the Florida Keys (Fig. 2). No such gradient occurs in suer,

however, man July teeratures averaging about 800-60F. throuaeut

the region. Length of frst-free season increases from a low of

about 240 days at the northern extremes to a high of 365 days in south

Flerida. The spread between daily vmxims and miniam taiperature is

greatly affected by proadaity to the sea, especially during the growing

season. Per example, the een spread for the anths of April through

September varies froa ea little as 140. along the coasts to as high

as 260r. in interior portions of the species rage (Fig. 3).









































0


ON








PEI

-j


C-C
0~

o



~~0
zH

0O 0

ULJ +)
0




Crd


~~+)






I.d

rd







C'Ja
u0

















cli,



CO\




OD













m a)

[13




CL cr
"C
LL L.
C>Q
LL '




C Ea r-I
I o4-3
t~l C>








r 0 0k\1
_I Q, O j
P.4 r-
I, 00 ro
~-ON
tr--4








Hem annual precipitation varies fro as high as inches in

seutheest Florida and southar Loudsisma ad Misisiippi, to a low

as 14 inches at the northern limits in east Georgia (Fig. 4). Although

the pattern is somewhat erratic there is a general tendmcy for decreasing

rainfall from southern Louiiae5a, eaet and northeast to South Carolina

md from south Florida northward.

Seasonal distribution of rainfall skews distinctive patterns.

Precipitation is distributed favorably in the northern portion of the

species range, with highs occurring generally in February and March,

and July ad August. In the south, meit of the total rainfall occurs

in the midsamer months and wintertime drouths are rather ceioon. The

variation expreeed in these terms produces contimuos patterns. These

are well illustrated in maps dmn by Squilllae sad Krams (1959) which

show patterns of rainfall for Janary through April, and June through

September. The same situation is also expressed in Figure 5 which

shows isogras for rainfall frem October through May as a per cent of

ampual. Note that it is low in extreme southwest Florida sad increase

rather uniformly to the north ad northwest.

Estimates of precipitation-evaporation (P-E) ratios were determined

for weather stations within the range of slash pine, using the aethed

described by Thornthwite (1931.) These ratios are measures of

precipitation effectiveness at are estimated from mea meathly pre-

cipitatien and mea~ monthly tea~ nature, utilizing Tho mtlwaite's

formula er his nomogr. (he latter, a grapbieel atMd, was w M

for the present study). eP-1 es wane wonI at

Februwy, March, and April, .io.. ....

because effective rtMwaia


























I 0.
Or


0\



1 01

r0%
) o



me
Sr0
0 T<






a)
'-4





H 0
Idp
Cd







a a)4



a)
-'4
Lr\






ff c


h ^







20























t0 0

od


0

a,











0 0
C )





4-'


OC,




-J ,d l.


C p e0 01
co c








O N
P4
0 r
S












H 0 'd


oA -4 a



I P4
i- z C
U
i CM m



-P (8 h
i- + (
ut-C p
i-l P
(U ^


( -
(-i





21

associated with growth of slash pine than rainfall during other periods,

as reported by Coile (1936). The data showed a distinctive, continuous

pattern (Fig. 6), mach like tht for October-May precipitation per eent.

Hurricanes are comon along the coastal areas (Weather Bureau, 1959).

Chances of hurricane foroe winds are greatest at the southern tip of

Flrida, and the probabilities generally decrease to the north along the

Atlantic coast to southeast Georgia where they increase slightly. On

the Gulf coast, probabilities decrease northward to the Tapa region

but then become high again in west Florida and south Alabea.,

Soils within the range of slash pine are for the most part sandy

in texture, and low in mineral nutrients and moisture holding capacity.

They are often underlain with hardpans 18 to 2~ inches below the surface.

Coastal areas are low and flat while the interior portions are generally

rolling, with gentle hills and ridges mostly under 200 feet in elevation

but reaching as high as 3k5 feet in Florida, and 600 feet in Georgia.

local variations in soil characteristics, frequently associated with

aall differences in elevation (as little as several feet), are eoamen.

These variations strongly affect tree growth (Cooper, 1957).

Forest geneticists are concerned as to whether or not racial

differemees associated with local variations in soils are present.

Edaphic races have been reported fer ame species of plants (Snaydon

and Bradshaw, 1961). obet workers feel that this type of variation

has not developed in slash pin. Until recently, slash pine occurred

only on pond nargis. *Natural selection probably has not had sufficient

time to cause appreciable changes in gene frequencies on the higher areas,

especially since these areas frequently are interspersed with flatweeds.



































C c
t 0 \




"- 0 0 0
0 0 -\
. 4Drl H


0 0
--- -
4-) 0
03 OC




0 ?-t %



- 0 -&C)
4 0

oa




So
SI-
Q


i -P
.J<




z c -'
4I

I $- *\

S*r4 -P 0\
PO 0)\
0


M 0 f









*1-4
F- 4






23

Geological changes during the Pleistocene period (beginning about

3/4 million years ago) undoubtedly had ane bearing on the development

of variation in slash pine. Following the Kansan glaciation,the Florida

peninsula was reduced to a group of small islands extending from Hamilton

County in the north to as far as Highlamds County in the south (MacNeil,

1950). The second shoreline recognized by MacNeil, following the Illinoian

glaciation, shers a similar group of isluads but they were larger and

the mainland extended as far south as Alachua County. During the mid-

Wisconsin glacial recession, much of Florida occurred as part of the

mainland, the peninsula extending as far south as Glades County, with a

number of islands mostly along the east and southwest coasts. The final

and most recent shoreline recognized by MacNeil was of post-Wisconsin

origin. Although the degree of inundation was relatively mall at this

time, a number of islands occurred along coastal regions.







Pasatal Ihterial

the conventi eal seed owee teelique ws used for this study

but with the additional features of: (1) empling paretal materials

to me us ge qambhle varl aie, a (2) milxteiag individ l mother

tree identity in order to study Ibber te variation within stands.

In the fall of 1960, abu comes ad follage emple were collected

from eah ef five (in a few irnstaces le) mother trees at each of 55

stsms scattered lthreegot the rage of lsth pine. Proposed stead

locations were prendesiated -aLly by gridding the are on a ma, with

a spacing interval of ebut 50 miles. Neoever, rimegaeity of the

species rang, nn-feoeeted areas, amd other aeosirations aeseesitated

moving may of the proposed locations so that the actual distribution

of the stuids only faintly resembles a grid (Fig. 1).

It should be noted that systematic amsling of stads leds te a

bia in veriace nd the um idtude of this bla is 1w iMm. An

alternative proedwue weald have been to sa le stesl eaepletely at

randeh or to startify ad emle raRdoly within strata. System ic

sampling wa eboeen beeaue ef a strong desire to inetwe the extremities

of the rage, ad becoeee it vas felt that this mthed would be meet

suitable for elucidating patterns of variation.

Materials were collected through the aid of cooperators. Instructioas

included selection of accessible, natural stas as We as feasible to

the prodesigeated point., with the rCeuirmats that they (1) be at

lest 00 feet y from flowering slash pine platatioma, (2) be of

fruiting age, ad (3) not be selected for aay particular traits.

24








Within each stand, mother trees were selected randomly but with

restrictions that (1) they be dominants or codoinants, possessing mature

cones, (2) they be at least 200 but not more than 1,300 feet apart, and

(3) they have one or more neighbors within 100 feet. In those areas where

the two varieties meet or overlap (transition zone), no attempt was made

to select one or the other variety, because (1) identification of the

varieties in the mature stage is difficult, a noted earlier, and (2) it

was felt that attemptcd selection would prevent the possibility of

determining the population structure of lhe transition sone. Mother

trees within stands were designated "A" through "E". These letters,

combined with stand s (1 through 55), served to identify all

mother trees.

From each tree, 10 to 15 cones and 5 branch shoots were collected

frm the upper and outer portions of the crowns. Most of the materials

were obtained by shooting the out of the trees with a rifle. Plant

materials were seat to Olutee, .Florida, for processing.

Collections were highly successful but, upon receipt of the

materials, the *e le from stand 51 as found to be loblolly pine

rather than slash pine (identification was verified upon sowing of

seed). Hence, this stand was discarded. Also, materials for three

mother trees (291, 48A, sad 48C) were missing. Finally, it was later

determined that mother tree 21D was apparently a hybrid (or backeross)

between slash ad longleaf pines, and hence data from this tree were

eliminated from analyses. These circumstances reduced the number of

stands to 54, and mother trees to 266.


a!iiii nR ........






26

In the late fall of 1960, after eone collection, seven additional

stands were designated (nmaers 56 through 62) ad used for collection

of foliage sales (see Fig. 1 for location of these). Thawe s pplemntery

sales were taken mainly to check em what appewed to be unusual results

from the main sales and to increase sapling intensity in north Florida.

Data from the supplemental sales were not used in statistical anlyses

but were inclated with data from aain sale in elucidating patterns

of variation.

Upon receipt, the unopeed coae were counted and 10 (or less when a

shortage occurred) were selected from each mother tree ad photographed.

The negatives were then projected on a microfilm reader ed the lengths

and dimeters (across broadest portion) of each come were measured.

Cones were dried in the open air; then the seeds were extracted aad

wimaowed with a seed blower which removed practically all empty seed.

Full seed were then counted, weighed, and stored in a refrigerator at

approximately 400F. until plated.

Branch shoots were handled as follows: Eight fascicles were taken

randomly freo the central portion of the first flush of the 1960 incremnt

of each branch shoot (40 fascicles per mother tree). The number of

needles per fascicle was determined on each of them. Then 3 fascicles

were selected randomly from each group of 8 sales (15 per mother tree),

and on these the lengths of fascicles and the lengths of the fascicle

sheaths were measured. Finally, 2 additional needles were selected from

each shoot, again from the central portion of the first 1960 flush of

growth (10 per mother tree) ad the uppemost 2 inches f each was cut

and preserved in foramlin-aceto-ethyl alcohol fluid.








The preserved needle specimens were then used for additional

measurements as follows: The lower 1/8-inch of each section was cu

and examined under a binocular dissecting microscope (45X) and the

following measurements taken: (1) Width of the needle, measured across

the flat surface or surfaces (biaate needles had one flat surface while

ternate needles had two), using an eyepiece micrometer; (2) the number

of rows of stomata on the flat surface or surfaces; ad (3) the number

of staoata in two rows, ea 1.68 millimeters long (the length of the

micrometer scale); for binate needles the second row nearest each edge

of the single flat surface was used, while for ternate needles the

second row nearest the rounded surface van taken from each of the two

flat surfaces. The number of rows of stomata was divided by the total

flat surface width in millimeters to obtain numberr of rows per millimeter

of width." The number of ros per m. of width was then multiplied by

number of stomata per am. of row to obtain number of stomata per square

am. of needle surface.

Freehand cross sections were then cut from the lower end of each

of five needle segments (one per shoot) and wmunted in water on

microscopic slides. These were then examined under a microscope (100X)

and the number of resin ducts and number of layers of hypoderaal cells

determined. The latter measuremeat proved difficult. Invariably there

as a well defined, thin-walled, outer layer of cells. Inside of it

occurred one or more "layers" of thick-walled cells, but these were not

always in true layers, the inneraost frequently containing sporadic,

single cells. However, four points were systematically predesignated

on each section (always between staata) and the number of "layers"

counted at each, to obtain an average for the needle.








Progey MataeIl

Seeds were soe on March ~1-15, 1961, in a nursery at Oltee,

Florida, in two nursery terts. Nursery Tet 1 wa xdigned to obtain

Mcn develgeat of foliage, md for this roemen needs wnee me

in plastic pets 6 inleb in diameter a 6 inews deep. luh design

vs a rmadmied bloek type, with individual tree plots m five

repliationm. FroP oeo to three se*s were som per pot, dApading

wiom the amber wnalable, al t the seedlings r thine to me per

pet son after grmiation.

Nursery %at 2 was designed ma ily to pehduo seedlings in

quatity for outplating, vhish is not rmeeesSw o in this report.

Hwever, the material provide a epportialty to obtain mre liable

sta ,a oned g emindwti an oetyledea n n r then cauld be obtained

froa Nursery Test 1 a hbero vwa used for this pury e.

In Nursery est 2, seds of each their tre ware sewn in ar

plots of 44 sdees eh, with 3 replications. Nut in order to minimize

acpetitie effects, the five =rher trees of each stma were renWtdoed

within sted plets, mnd std pleot were radmined within repliesties.

Seds were awn at a spaciag of 1 inAh within rows ml raen were speed

6 inehes apart.

OaGi ntion wa eeowntd in Nirsery Test 2 a March 29, 1961, ad

again on April 10, 1961. The first count divided by the wneMed eat,

x 100, gwae a inded of the speed r rbe of geamiatioa in per aent,

while the latter coumt (e ireed in per aent of seeds son) alme Wa

sed as a nosure of gelmi6ability. Alms, estylode co ts wear obtained

on up to 10 randeay choee seedlings per row in April, 1961.






29

Total heights and stem diameter outside bark at ground line were

measured on the seedlings of Nursery Test 1 on November 3, 1961.

In the late fall of 1961, foliar samples and measurements were

obtained from the potted seedlings of Nursery Test 1 as follows: First,

counts of the ln r of needles per fascicle were obtained on each of

10 fascicles taken from each seedling. Fascicles were chosen randomly

froa the upper portion of tih first flush of growth. The foliar

material was then handled in a armer similar to that from the parents.

However, here fascicle length and fascicle sheath lengths were measured

on three fascicles obtained from each seedling and the stomatal, resin

duct, and hypoderm measurements were obtained for two needles per

seedling.

Analyses

Single variate analyses

Statistical analyses consisted mostly of two types, single variate

and multivariate. In the single variate analyses the stands e divided

into three groups as follows:

Group i. Stands within the range of the elliottii variety, excluding

those close to the limits of the densa variety, as follows: Nubers 1

through 26, 31 through 40, 52, 5, and 55. Total, 39.

Group 2. Stands arbitrarily considered to be within the transition

zone between the two varieties: Numbers 29, 30, 41, 42, iA, and 45.

Total, 6.

Group 3. Stands within the range of South Florida slash pine as

delineated by Little and Dorman (1954): hKubers 27, 28, 43, 46 through

50, and 53. Total, 9.








Note that the aaaigment of borderline stands in the transition

zome Qepaws inconsistent in om instanees, according to limits of

the varietal ranges shown in Figure 1. The reaso for this is that

the asigment of stands into groups vas made aeerding to the mall-

scale map in Little and DoIn (1954), the most recent available range

arp at the time. fie northern limits of var. dansa shown in Figure 1

were reproduced from Lagdon' (1963) are recent ad detailed asp,

revealing what appears to be inconsistencies.

The purpose of grouping the stands vam to provide a mean for

determining the presence or absenoe of significant atand differences

within varieties. To this extent, limitations imosed by the arbitrary

nature of the groping should be recognized.






31

The analyses of variance for data from parent tree samples were as

follows:

Source of Variation D.F. Expected Mean Squares

2 2 2
Groups of stands (G) 2 7 + kl2 O + kU 0 1

2 2
Stands within roups (S) 51 oT4 + k22 0

2
Mother trees within stands (M) 209 CO-


Total 262

In the above analyses the deficiency in degrees of freedom for

mother trees was due to seven "missing" trees (9D, 21D, 29E, 36B, 48A,

48B, and 48c). Tree 21D wva dropped because of evidence that it was a

hybrid, while the rsaaining missing trees were due to lack of samples.

Coefficients for the variance components for all analyses of

variance were computed using the technique outlined by Gates and Shiue

(1962). For the parent tree analyses the coefficients were as follows:

k12 = 4.870 kkl = 56.464

k22 = 4.869








The analyses of rimoie for progeny data of Nursry Teat 1 were

as follows:

Source of Variation D.F. t peeted Mesa i a re


keplications (1) 4

2a 2 22
Groups of stands (G) 2 Oj + k13 Ui + k1l2 IC + k1 Cg

2 2 2
Stads within grpeps (s) 51 u j + k23 aM + k22 C

2 2
Another trees within stands (M) 209 dj + k33 0jj

2
Error (i) 1043 OR


Total 1309

In the above analyses the deficiencies in degrees of freedom for

mother trees nd error were due to seven "missing" mother trees (21D,

221, 29W, 42B, 4i B, ad 48C) ad five miningg" seedlings (7A-4,

9C-., 38D-1, 46C-4, ad 46D-4). M-ther tree 211 we dropped for reasons

noted earlier, while the reiaing missing items were due to laek of

sMeples.

Ooefficieats oeeputed for the oemponents of variance estimates,

were as follows

k13 = 4.982 kl2 23.746 kU = 2TT.504

k23 4.984 k22 24.278

k33 4.980






33

The aaalyses of variance for progeny data of Nursery Test 2 were as

follows:

Source of Variation D.F. Expected Mean Squares


Replications (R) 2

2 2 2
Groups of stands (G) 2 Uj + kg12 O- + kU G-

2 2
Stands within groups (s) 51 1+ k22 'S


Error 1 (z1) 106


Mother trees within stwads (M) 202 112 + k33 O-M

.2
Error 2 (E2) 404 0


Total 767

In the above analyses the deficiency in degrees of freedom for

mother trees was due to 14 "missing" mother trees (17D, 21), 22E, 25D,

29A, 29C, 29E, 330, 4lB, 413I 48 48C, 53A, and 530). Mother tree

21D wva dropped for reasons noted earlier while the remaining trees were

dropped because of lack of samples.

Coefficients cemputed for the ccponents of variance estimates

for progeny data of Nursery Test 2 were as follows:

kl2 14.061 ku 159.140

kp, 14.223

k33 3.000






34
The main purse of the malyses of variuee w to obtain objective

estates of the degree of variatieio Mseciatd with the freters studied.

To aid in doing this, estimates of compeaets of varier were obtained

using the sen squures comuted in the aalyse of varime and the

"eapeeted oma square" shew above (Saeeer, 1956, p. 261). The

estimated coempoaets obtained in this m r vere finally expressed in

per cent of the total of all eempmrets (xKeludiaR the "replicatima"

eemReat in progeny data).

The c ompoaet of variaoee assocIated with groups as eo idered to

be expressive of the division of the species iant the two varieties ad

the tradition smea. That esuseiate with stands within gro s expresses

the degree of geographic varieties within varieties. These tw oompments

taken together are expreesive f geographic variation for the species as

a whole. If either or both of these ecampats were statistically

siaifieant and appreciable in maaituie, isegrp were druw in an

attempt to eluidate the pattern of geographic variatia for the trait

concerned.

Nete that the above analy ses ws hm bgemoe vari ances. As

vill later be seen, variation was freuetly fead to be greater

in sea pertioes of the species range thra i ethers. This eirematece

affects the validity ea the estimates of variaee eapements and the

significance tests. Hence, the estates and tests should be considered

as appreximaties.








Multivariate analysis

tiltivariate aclysis as employed to eamine the pattern of

geographic variation oonaidering a group of traits asiftaeously.
ghaulanbia' generalizedd distance function" was eboen. (For

discussions of this and other aultivariate techbiqces see Rao, 1952;

B~e~w 1960; Wells, 1962; Wrigt and Ball, 196e; an Mmtieng, 1963.)

This function, B2, presses the Legree of relationship between two

populations, considering sailtanemm uly the group of traits chosen.

The formula for two traits (X1 and X1 is am folles:

D2 (,u It)2 + 1u _112) ya ya2) + (r.-X2 a)2
812 S12 S
in whieh i and 112 are the ewns of trait I for the first and second

populations, respectively; X1 and Zg2 the means of trait 2 for the

see two populations; 512 and S22 the peeled estimates of the variances

of traits 1 and 2; iad 812 the oovariaee of traits 1 and 2.

As can be seen, the manitude of 2 for any two populations

increses with increasing difference in the mnsa for each trait, and

dereases with increasing variane and eovarianee within populations.

Per mare than two traits the formula is more conveniently expressed

as follows: Z S 1 a d
i j ij i j
where i i the een population difference for trait i

and d& the mean population difference for the Jth variable
-1
and Si the element in the inverse of the corariance matrix

oerreMpnding to the ith and Jth variable.






36
Using procedures outlined by Rlo (1952, pp. 345 ad 357), D2 values
were cauted for 17 traits, including 4 fro the parent tree data

(coem legth, come dimeter, seeds per eem, d seed weight), ad 13

from progeny data (total height, stem difmer, amber of termate fascicle,

needle length, sheath length, owv of stomata, steta per m., strmta

per sq. m., resin ducts, hypodemr thickness, gemnability, speed ef

geannation, ad cotyledea manber). Since theee were 54 tands or

"populations" a total of (54) (53) 1,431 values of D2 had to be coe uted.
2
The wek was dore vith IBM 709 electronic computer at the University

ef Florida (Gaouting Cater.






RESULTS AND DISCUSSION

Results of the single variate analyses ad patterns of variation

for indivdual traits will be presented first. Following will be a

recapitulation of the individual trait patterns along with a discussion

of possible causes of variation. Next will be an analysis of the

degree of variation (diversity) among individuals within stands and

among stands within varieties sad their implications. Then follows

the results of the nultivariate analysis, and finally a discussion

of taxonemic considerations.

Single Variate Analyees

Cone dimensions

Mother tree naws of come length varied from 7.0 to 15.5 ca.

(Table 3). Most of the variatien was associated with mother trees

within stnds but stads within group aecownted for a considerable

proportion (22 per cent) of it (Table 4). Since little of the variation

was associated ith groups of stands (6 per cent) the trait was net

distinctive for varieties. The stand-to-stad variation exhibited a

fairly distinctive pattern, however. Cones were relatively short in

southeast Florida and increased to the north (Fig. 7). An east-west

waxiam occurred near the Georgia-Florida beudary (Walton County,

Florida, to Daval County, Florida), abeve which cone length decreased

slightly.

Variance components for come diameter were rather similar to these

for come length, with stands accounting for a sizable proportion

(37 per cent) and with groupings of stands accounting for none of it.

Although te variation mng stands was net associated with varieties,

a fluctuating clinal pattern was apparent (Fig. 8). Cones were thickest
37










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in the collection from Collier County, Florida, ad they deeresed in

diameter toward the north, east, ad south. An eat-veet trough seemed

to occur in the neiglberhood of Pelk Coaty, Florida, ad either extending

seothwest-northeat through the northern portion of the species rage,

with a ainimu at Brantley County, Georgia.

The cone dimnsiom foed here (Table 3) agree fairly well with

values reported by others, seen by the tabulatiae of "eomOr" ranges

below. However, it is dbvlous that these eome dimension re not

particularly useful for identifying varieties.


Authors



Sml (1933, p. 4)

Caker and Totten (1937, p. 19)

Little ad Dorma (1954)

Waseley (1954, p. 198)

west d Arnold (1956, p. 5-6)

ward (1963)

Present study (ranges among
mother tree mans)


Little ad Dorman (1954)

Wakeley (1954, p. 198)

Present study (ranes mosg
mother tree nea a)


Both
elliottii dmeas varieties

Leagth--cetimters

8-12 8-15 --


9-li4


8-11


7-12



8-15


8.2-15.5


k-5


3.1-5


7.0-15.1


Dismter--oentimters

3.5-5.0


*3 2.7-5.0


6-14



6-15


7-16

7.0-15.5


3.3-5.6

?.7-5.3








Seed yield

Seed yield was extremely variable both mong mother trees (1 to 127

seeds per cone) and ong stands (3 to 97 seeds per cone) (Table 3 and

Fig. 9). Much of the variation among either trees was associated with

groups (22 per cent) ad stmads within groups (32 per cent) (Table 4).

Variation mong stead means fell into a irregular clinal pattern

(Fig. 9). Som of the irregularity may be due to differences in stand

density or similar factors not studied. A high occurred in an area

centering at Thomas County, Georgia, with a moderately high ridge

extending to the east sad vest. Yield usually decreased from this

ridge both to the north and south, reaching a extremely low point at

Big Pine Key, Florida.

Since seed crops generally vary from year to year, and since

locality by year interactions are probable (Tousey and Korstian, 1912,

p. 105), one should not assume that the pattern of seed yield per cone

found here would be consistent in time.

The mean sound seed yield found for the whole species, 51 seeds

per cone, is lower than a reported by Wakeley (1954), 60-70 seeds

per cone. The discrepancy may be due to yearly effects as noted above,

or to differences in the degree of winning.

Seed weight

The eems of seed weight for mother trees were extremely variable

(10 to 51 ag. per seed) (Table 3) Much of this variation was associated

with stands ad it exhibited a clear, costly clinal pattern (Table I and

Fig. 10). A nertseast-seuthwest trough occurred in southeast Georgia

extending from Pierce County to Evan County. Seed weight increased in









































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46
all directions from this area. To the srath, a aertheot-southmest high

occurred extending freo Dixie Comty, Florida, to DIu.i Ceaty, Florida.

It then decreased irregularly to the south. ote that the rate of Shage,

however, was not mifora, the drp being the shampest in south Florida.

The mea seed weight for all treeo, 30.6 ag. (vbick eeonerts to

about 14,800 needs per lb.) agre we ll with the reges for slash pine

giWve in the Forest Servioe Woody Plant Seed Meaial (Anonymous, 1948,

p. 269), 13,000 to 16,000 seeds per lb. ad else with the rages of the

mess of 100-ned aplee, 2.8-3.5 grm, givew by W eley (1954, p. 198).

Germiability and speed of gepriaetiea

GeriLnbility of seed varied highly among thker trees (6 to 100

per cent) (Table 5). Sianiflomst amoats of the variation were

asociated with stads and groups (17 ad 6 per cent, respectively)

(Table 6). Geriinability averaged highest in the daeme variety, next

highest in the transition soe, ad lowest in the typical variety.

However, the pattern seemed to contain a large elemt of radeumes

ad sa ilogre were drum (Fig. 11).

The result agree with Mergen ad Hookstra's (1954), in that

significat differeaes a seeed lots from different portics of the

rage of the typical variety were foand ad that no distinctive pattern

occurred. However, the differeces i geaeinability of seed from

comarable areas in the two studies showed little agreement.

Germinability of seed ma of oeone be affected by maturity at

time of collection ad other factors. Althagh attempts were mde to

collect only mature comes, there is no asuramee that all lets were of

the see degree of maturity. Hence, even tbui siptficant stand













Table 5.--Meuws and ranges of variation for progeny
data of Nursery Test 2


a Speed of Cotyledon
Group : Germinability : pee io b :Cotyledon
Sgermination

Per cent Per cent Number

MEANS

1 60.7 67.1 7.43
2 66.7 75.3 7.29
3 73.2 89.4 6.83

All groups 63.3 71.4 7.32

RANGES AMONG SEEDLIN S

1 -* -- 4-12
2 -- 4-13
3 4-10

AMES AMNDG OTH5R TRIED A3E

1 6-96 0-99 6.0-9.4
2 23-91 7-100 6.2-9.3
3 14-100 53-100 5.5-8.0


Per cent of sound seed geminating within 27 days after
sowing.

b 15-day g nation x 100.
27-daw gezraiation












Table 6.--Wemn sqwrtees n esti be at variance components obtained
from anamlyes t varianee of progeny data or Nursery Test 2


: Geriability : o Cotyledon
: germination

MNR SIARas

Replisations 5,027** 135 .199
groups 8,271*- 25,163** 17.743"*
Stanids/G 1*l14* 1,8146* 2.106*
Mirror 1 131 0o .067.
Mother trees/S 833" 978@ .*597**
Error 2 86. 192.. .065--

ETIMItTED CQMPOnH OF VAIANCE--PR CUBT

Grn-pu 6 13 17
Stands/G 17 9 24
IrrOw 21 37 15
Mother trees 43 4 29
Errr 2 13 17 15


* Significant at the 5 per cent level.
- Significant at the 1 per cent level.








49














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differeacee were found they were not neceaearily genetic in ntwre.

Speed of geminstion also vaeed greatly mog mother tees

(from 0 to 100 per cent) (Tale 5). Sipifieemt properties of the

variation were accountd for by goupes ad stemds (13 ad 9 per cent,

respectively) (Table 6). The stand aviation edhibited a distinctive

clinal pattern (Fig. 12). A lav occwurd in Wsre Cotaty, Georgia, which

also tended to ext d westrwd to Holmes Comty, Florida, ad Catalina

Islmd, Mississippi, and ertheo twrd to Georgetoa Conty, South

Carolie, as wll. Speed of gezmintion imeremed both to the merth

ad to the south of the trough.

Evidence of racial variation in speed of geminatimo has also beea

found in lodgepole pine (P. contorts Dougl.)(Critchtield, 1957), eastern

halock (Tsuga medeais (L.) Garr.) (Sterns aRd Olson, 1958), spruce

(Picem) (Schell, 1960), ad ponderosa pine (Callham, 1959 ad 1962).

Like gexriuability, differences in maturity of seed could have had

scm effect upon the differences in speed of germination amog stdts.

However, the nature ad distinctiveness of the treads practically rule

out the possibility that such extremeous factors oould have caused the

pattern. Mere likely it was due to geetic differoenes in the mdi,

brought abont by natural seleetie ad causing differential response to

eviroerMtal stimuli.

It is of interest to speculate en the nature of the gemetic

differences that were apparently present, ad on the particular

envircmsatal factors to which the eeds responded at the planting site.

paft studies suggest that teperature is a ajor enviroma~tal factor.

According tb Callaha (1962), the speed of germination of tree seeds is






































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a

o
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52
governed primarily by toeprture given adequate moisture ad light, with

geainatie prooeeding mot rapidly at meo optiam toemeratwe. Iuperi-
seats by Jones (1961) suggest that pheeoperied was not a preominuat factor
in casing the differences in rate of gerinatie. he shoed that a
single expeware of slash pine seeds to 15 aamite of daylight Saouled the

total garminatieo per ent ever that obtained u r complete darkness.
But illumination periods of 8-, 12-, en 16-hours used ne differences
in either speed of germinatieo or total glerniatieo per seat.

Assuming that temerature was a mjor eavirommetal factor, one
might speculate that the seeds pesesM ed different geetieally-fixd
optimum teperatures ed this would be reflected in different rates of
gemination when the seeds were planted in a eemn environment. Such
was feod to be the case through laboratory tests by Callaha (1959 ad
1962) for pondeessa pine. Hmwer, this seme would net explain why

seeds brought north from south Florida and south freo the northern
limits te Olustee, Florida, garmiated early.

Preeeaee or abeeee of seed dormacy my here been iwmprtat. In

ex ining this possibility, it is well to review what is knom aohut

factor that my be involved. Moet slash pine *eed are shed in October

(Cooper, 1957). Under natural editions, seed tend to gerinsate in

spring, ut when soil moisture is adequate oesierable germinatieo my

oceur in early atmn (berr, 1959). In esoth Florida, eeodities for

early fall gsemination would see to ccur rather frequently because

Oetober rainfall there nerages about 6 inches. In eeatrast, October

Sriafall arerages about 2 inches in the north. In the south, the

winter months are dry (average rain about 2 inches per math) ad

relatively vern, vhile in the north they re wetter (about 4 inches

per maath) and considerably cooler.






53
Stored slash pine eeds show a mild degree of dermancy, germination

being abetted by stratification, while fresh seed do not (Anonymous, 191 ).

These findings on dormncy were most likely based upe work with the

typical variety of slash, although this int is not certain.

It is possible that dormacy may be more characteristic of northern

seeds than southern seeds. In the north, if the seeds.do not germinate

promptly in the fall, there would likely have to be a mechanism built

int the seeds to prevent germination over winter, because of te danger

of cold temperatures to newly germinated seedlings. In the south, e

the other had, there would not seem to be a need for dormacy, because

of the wra winters. In fact, it would seem that gerAination as early

as possible after seed fall would carry a high selective advatage--

propt germination to avoid mortality fros severe winter drouths.

The feet that northern seeds will germinate promptly under favorable

conditions in the fall suggests that oaset of dormancy (if it actually

occurs) is delayed. Prempt fall germination undoubtedly carries a high

selective advantage--trees germinating in the fall obtaining "a heed

start" on those germinating in the spring in regenerating denuded lands.

However, prompt fall germination under suitable weather conditions plus

dormacy when weather conditions fail would seem to be the best ocibination

for the variety. Theee cojectures on dorancy are feasible in view of

the findings with several forage species a Europe, in which it was shown

that germination characteristics of species inhabiting different climates

were closely tied in with dormancy mechenisms (Cooper, 1963).






54
Aaeunng both differential daormn y ad different optiman temperature

requirements, we might attempt to explain the results of the present study.

South Florida seeds gerxmiated earliest because they lacked doracy.

Seeds frso south Georgia ad orth Florida g rainoted late became the

stored seed possessed a mild degree of dormey--hac the seed been

stratified differences m y not have bees foead. Seeds from the extreme

northern limits of the speeles rag garminated promtly beoeese, although

they also posses. moderate dormcy, their optimi teeratwr was

attained sowr, having been moved fron a northerly to southerly direction.

The latter conjecture asaes no differamse in optira typcuratre

requtirents within the northern regnia. Of course these are little

ern them gueses, further eaperimatilon being neesoeery on this

problem.

Cetyleedn ~mber

The number of cotyledons per seedling varied from low as 4 to -

high as 13 (Table 5). Much of the vaiartiom ws oasoclated with stmda

(24 per cent) and graVe of stamds (17 per cemt).

Stad average displayed a distinctive clinal pattern (Fig* 13) tuch

like that for seed weight (Fig. 10). On the average, otyleden numbers

wee higher in the north then in the soath (Table 5). However, as sen

in Figae 13, the pattern is neh mnre subtle tha this, with a law

occurring in the north m well in t the south.

The means ad rges agree fairly well with pervirely reported

values, a indicated in the following tabulation (mees are folleved by

rages. in parentheses) .















































W

LL
co

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C,)
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Author


mlliottii dirme
- NuersI of cetyledBns


tneelmm (1880, pp. 174, 186)a

Butts ad Buchholz (1940)

Little ad Dorms (1954)

Daeoto atiemol FPrest, Mms.

Clinch CeOty, Ga.

HOadry Ceouty, Fla.


56
Both
varieties


8(6-9)b

7-73(5-10)b


7.36(6-9)

7.72(5-10)


6.76(5-8)


Pr eet study (rags are 7-43(4-12) 6.83(4-10) 7.32(4-13
ang seedlings)
a Cited by Little ad Borm (1954)

b Origin not specified

he eerrelatice between cotyledon amer amd seed eight n a s tand

mm basis was .7, highly signifio t; the pooled correlation for mther

trees within stads as .42, alms highly asiifiomt.

Reil variation in re pet to cotyledon mbear hs aLe been found
in loblolly pine (ThoaJbjomsen,1961). The positive correlation between
seed weight and eetyledo number agrees vith findings by Buchhels (1946)
for penterosa pine.
Tetal height
One-yew-old seedling heights varied greatly ad the majority of the

variation (66 per est) vas asseiated with gro~ ings of the stads.
Seedlings in the Derthern portion of the species rage were tallest
(Tables 7 aTd 8, at Figs. 14 anB 15). Variation in the north was
relatively sL1- but heights deceased rapidly going frn north to meuth
through Florida. Thus, the pttera is largely ruat in the morth ad
clinal through Florida. There was also a modest eat-vet gradient


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Figure 15.--0a-year-oldA las pime smalings, baring differmees
in total height a stem dimiter. Upper $tlre reprenumt a
latitudimal tramset thrum k the species rag., the -me a the
exteme left beig from lig Pine Key, Frlrin a e me- a
the extreme ripit from SmC er Corsty, Qergia. Lewr pwhte
shrws diffeuremas betrW a tree from the vwt mst (the tw
trees a left), the interior (e3 ter two), d the east eeo t
(tie two Om riet) of eantraul Florid.





61




..............:::::
iniii: .. ':: ii :" ":':i E :iii :i i mi iiliii;E:::: ..:iiiiM



















::: ........~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~.. .........................::E iE:::::::::EE:.. .:E

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tbeosu central Florid seedlings being tallet in the center of the

state, eat shortest oeang the sets.

In a gnral way these reeouts are in haamay with Little and orams's

(19 ) ume of st height as a diaosttie fetifw for ideatifying varieties.

Iwever, beewme of the gradient in rForida it paemntly would be difficult

to clasify seedling in the transition sme.

The faet that seedlings in the north-eentral region were not

particularly taller thae those at the extraities of the north, seems to

diagree with finding by Sqtillace wd Kraus (1959). Ever, seeds

wre relatively enl m ad germinatian relatively lbte in the north-central

region. fshe two factors apparently had sem effect upon heights. The

within-stand pooled correlation eeefficient between seedling baight mad

seld eight as .31 (sipifilent at the 1 per cent level) msd between

seedling height nd rate of gerdnation, .17 (sigpifient at the 5 per cent

level).

On the ether hrd.n, the serfiority nl early height rowth of tree

fta the north to those of the sacth is great enough to be rel in spite

of soed weigt ad rate of yrerLnute effects. RBeses for this

differesee probably lie in the fact that the seth generally suffers

from artrems of climatic ad other enviramtenl cneiti es more so

tiMh doe the north. Such factors could include poor rainfall distri-

buttio with frepqnt dreaghts in spring nd flooding in samr, disagim

toupietl terms, ad paolbly frequency of fires. In the sewth, natural

selection is probably relatively strong for resir~ta e to these factors,

htbeh mnr came relatively weaer selection for rapid grorh thai in the

north.








Admittedly there are alse climatic extremes in the peripheral

portions of the north. For exmle, relatively oeld temperatures nad

frequent ice stems are characteristic of the area Just south of the

northern limits; tropical sUtor are relatively frequent along the Gulf

coast; rainfall distribution is relatively amfaverable along the coasts

of Georgia ad South Carolina; eeoditions conducive to fusifera rust

dae seem to be ast favorable at the northern extremities (McCulley,

1950).

The east-vet gradient through mch of Florida ay be associated

with the difference between men amxim and mem liniuzm daily

temperatures (Fig. 3)-trees tend to be tall where the temperature

difference is relatively high. This possible association is supported

by findings reported by Krmer (1957) and Mellers (1962)--in laboratory

tests leblolly pine and northern red oak (Quercus rubra L.) grew fastest

under the greatest day-night temperature differential tested

Stea dimter

Variation in stem diameter showed a moderately high racial compement

(25 per t for groups and 6 per cent for stand within groups) aad the

stand ieans exhibited a cliaal pattern (Table 8 ad Fig. 16). Stems

were thickest in the South Florida seedlings ad they decreed rather

uniformly to aertheast-southwest low exteading from Taylor County,

Florida, to Liberty County, Georgia. North of this trough, dimeters

increased slightly, but were not as large as those freo south Florida.

Stema usually were thicker (especially relative to height) along the

coasts of Florida than in the interior.
Thick steps are a indication of a carrot-like taproot. Thus, in
a general vay, the results aree with Little ad Doran's (1954) se of













































k
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this trait as a diagnostic feature. Stands in groups 1, 2, and 3,

averaged 7.1, 7.4, and 8.5 an., respectively. Trees from stands near

the northern limits of the species range had moderately thic stems but

they were taller than South Florida seedlings and hence would not detract

from diagnostic utility of this trait. However, like tetal height, the

difficulty is that because of the clinal nature of the pattern it would

apparently be difficult to classify trees or stands in the transition



Thickness of stem in slash pine seedlings has undoubtedly been

important in natural selection. South Florida seedlings, which charae-

teristically have thick stems, are more resistant to fires t north

Florida seedlings (Ketcha and Bethuan, 1963). Apparently, this

thickening of the hypecotyl, which is mostly dead outer bar also

inner bark and weed, imparts a degree of insulation against heat (Little

and Drnaa, 1954). The thick stem also probably provides a means for

string food, utilizable for sprouting when the crown buras. Hence, the

trait is assunid to have resulted a an adaptive response to fire (Little

and Boman, 1954).

If the trait is an adaptive response to fire, one would expect that

the frequency of natural fires, or the extent of damage from fires,

increases gradually from north to south, following the pattern of variation

in steA thickness. No concrete and reliable data could be foeid to check

this possibility. However, as noted earlier, slash pines in the north

were originally restricted to pends, pond margins, and ether wet areas.

Hence, it is possible that fires in the south invaded slash pine stands

more frequently, and perhaps were more intense, than in the north. Extended






66

late winter and early spring rth.s id ba d w inter taorstn es, ieem

in the mokth, my be faeters affecting the frequmey ad intensity of

fires.

egressieas wer eaulated te tetertnde factors that mijkt hawe

beea involwd in the qaparm t natural seletles a stem dim etr. Ste

dieter (stuad mws in oatitiJrs, Fig. 16) was u as the depaledt

variable. Indepaaatt variables used were s follows: (1) latitude

( sltm vales in degres); (2) the se of preeipitwitem-evtapMrtion

(P-E) ratios for maths of Febrary throv April (stend values, Fig. 6);

ard (3) mee Jaiwry tmperature (etat vales it F., Fig. 2). P-I

ralos (used as a mease of late winter-erly spring drouth) and

Jansry tamperstwe wrre eemsmeered as possible enviremamal faetrs

eaing netwall selection. Laitdle in itself weevl not, of seewse

Ceoe natural seleetilm, but the variable wa inelued to test the

apparently strong latitudinal trea and to see if effects of P-I ratios

at tdmpergture, iantpedientD of latitWue, ooulA be shAm. The aalyses

included simple, mIltiple, ad eurvilinear regressio Results are

sheen below.

Simple Iragraion Analyses

*eeffietats of
StIe diameter (T) m: Regrusie aoeffielante detetinatie

Per eat

Latitude (Xl) -.0232 0.l**

Feb.-Apr. P- ratios (X2) -.o02 15.6

Ja. te erature (x3) .00 36.T**







Multiple and Curvilinear Analyses

Standard partial Coefficients of
Ste diameter (Y) on: regression coefficients deteramiation

Per cent

X amd X2 -.615, -.031 40.2**

X aad X3 -.702, -.072 40.1*

Xl, X2, and X3 -1.111, -.205, -.631 40.8*

xI and X12 -6.649, 6.000 48.1*

Salad X32 -2.765, 3.385 46.8**

** Significant at the 1 per cent level

In the simple regression analyses latitude shoved the strongest

relationship to steal diameter, as indicated by the coefficients of

determination. This suggests that some envireanntal factor, correlated

with latitude, was instrumental in causing the stem diameter pattern.

The regression coefficient for temperature was almost as strong as

latitude, while that for P-E ratios was considerably weaker, but still

highly significant. Multiple regressions showed no significant increase

in the variance accounted for (indicated by the coefficients of determi-

nation) over and above that aceounted for by latitude alone. This wae

due to high intercerrelations between the independent variables. Therefore,

there is n proof that either temperature or P-E ratios had effects

independent of latitude. Because of the reversal in trend ef stem diameter

in the north-central area, curvilinear regressions were tried for latitude

and teaerature. Both regressions accounted for significantly (1 per cent

level) more of the variace above that accounted for by respective linear

regressions. However, latitude still was superior to temperature.






68

Frm the malysis we em oly oaeel te that the latitudinal tread

in sle diameter, with a reversal in the arth-eetral ves, was

sipifieant. Sperature ma P-L b le my hme had am real asoeiation

with the trmA, but sum other emviremmital factor rmt also be involved.

Jedles per fascicle

Both blamat ad ternate faeielcas were fomd In the parental m loes,

but the relative freqacies varied emsiidew ly a- indiested by average

ambers of needles per fscicle (Table 3). Strm differrmees displqed

a very distietive pattern, with a north-south high in eKtrme southeast

ealgia and northest Florid, and another n rthwest-seothent high in

nrth-eentral Florida (Fig. 17). Needles per fascilee iually decreased

grahially war frm thee hi~g A notable feare was that, although

ealers wer lo in a uth Floriae, they wer also usually low at the

emttrities of the species zra Thus, the results do not gee well

with Little and orrma's (195) reeemmedi u-e of this eharector for

sweoating varieties--diff mnees in sepling teetlique mr have eased

the dtaepement. Average ~mer of needles per faeilee in the proenies

w- g-erely higher tha in the premts (Table 7). his my be due to

an effect of tree age, or to the fact that the progmies, being prw in

a nwsery, had a are favoreble eviremmat the trees tader natural

osaditims. A very few proegmy faselles eantained four needles ald o

eateaied five.

The pattern of vsrictim moeg stads in the progenies was somewhat

similar to that in the parents (Fig. 18). However, the twe prewmamet

hirhs fold in the parts were less notieable in the progmies and

alse the difference between sefth Florida ad the rimat r of the species

rage was more proMomood in the progelies.









































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71

The pattern of variation in both parents and progenies seems to be,

in some respects, associated with severity of environment. The low in

south Florida coincides with unfavorable distribution of rainfall and

the low in the extreme north is associated with cold winter temperatures.

Somewhat similar trends have been reported for ponderosa pine. Needles

per fascicle in ponderosa pine tend to be low in eastern portions of the

species range (Weidman, 1939; Haller, 1962; and Wells, 1962), where the

climate is relatively severe and the trees are generally slower growing.

The results agree with Shaw's (1914) statement that in some species of

trees the number of needles per fascicle is dependent upon climatic

conditions, smaller numbers occurring in colder regions.

The apparent relation of needles per fascicle and severity of

climate may be associated with photosynthetic efficiency. It can be

shown that a ternate fascicle has about 20 per cent more leaf surface

area per unit of needle volume than a binate fascicle of the same

diameter and length. Thus, a ternate fascicle, having more surface

area for absorption of light and for exchange of gases per unit of

chlorophyll-bearing tissue, may be more efficient photosynthetically

than a binate one. A binate type, on the other hand, would seem to be

an adaptation for conserving moisture loss or for frst hardiness, at

the expense of growth efficiency. High frequency of ternate fascicles

then may be an adaptation to vigorous growth in optimum climate while

a tendency toward a preponderance of binate ones an adaptation to less

favorable climate. These possibilities would seem to be worthy of

further study.







INedle length

Needle length in the part trees exhibited a rather complicated

pattern of variation mO sat s (Fig. 19). In eneiral, needles avraged

leader within the rages of variety daen the in the north (Table 3).

However, the tendency wea not unifeim highs recurring in the earth as

wvll as in the seth. Needles tended to be relatively long in the

coastal wree, suggesting a possible tie-in with the difference between

mewn minial-neen unmwa toperatures (Fig. 3). But the corelation

eofflcint between these tne variales w u iemagifioat (r -.23).

The pattern in the preoenies was slyler, eeatait ng a strong

slamnt of clina.l variation (Fig. 20). N edles vere generally long in

smutkh Forida (secepting at the mtrmew tip) and they tedLr sed mrthwwd

te a northest-southwest lov through south Georgia, and then increased

above th.s area. The pattern vaguly resembles that in the parent in

*tat needles were, on the average, longest in the ieuth (Table 7).

The ranges in lengths ef needles for parent material re cepared

agitast those shewn by ethers below.
Both
Author elliottil deas varieties

- Centimeters -
9erler (1931) 15-30
Eaml (1933, p. 4) 18-30
Ceker mnd Totten (1937, p. 19) 15-23a
West sn Arnold (1956, p. 5-6) 18-30 18-30

Present study rangess meug 15-27 18-31 15-31
other tree mans)

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Fascicle sheath length

Variation in fascicle sheath length in the parental data was strongly

associated with stands, none of it being associated with groups (Table 4).

But the pattern of stand variation was rather intricate (Fig. 21). A

significant feature was that a pronounced north-south low occurred

through the center of Florida and southeast Georgia.

In the progenies the stand component of variation was significant

but rather small, 11 per cent (Table 8). Stand means displayed no

particular trends, with a large element of randomness (Fig. 22).

The ranges of variation in sheath length found in the parental data

do not agree very well with reports by others as seen below. The dis-

crepancies my be due to differences in maturity of the foliage sampled,

or to differences in technique of measurement (such as inclusion or

exclusion of frayed ends).

Authors elliottii densa

- Centimeters -

De Vall (1941a) 0.8-1.3 1.0-1.4

West and Arnold (1956, p. 5-6) 1.3 and under 1.6

Present study (ranges are among 1.2-2.3 1.1-2.3
mother tree means)

De Vall (1940) considered fascicle sheath length to be very diagnostic,

it being unaffected by climate, soil type, tree age, etc., and that the

character was useful to separate slash and longleaf pine.

Stomatal measurements

Results of the three measures of stomatal frequency were similar in

that (1) in the parental data only mall amounts of variance were associated



























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78

with groups or stands, with the patterns of the stand meons being largely

randc; and (2) in the progenies it was possible to show patterns for the

stand means, although they were samewhat erratic (Figs.23 through 28).

A camon feature vas a tendency for stomatal frequency (r.1 three types

of measurements) to average relatively high in the north and low in the

south, and also soue tendency for a high to occur in the north-central

area.

Mergen (1958) found a clinal pattern for stomta per ma. increasing

from est to east in slash pine progenies from 12 sources encompassing

ruch of the northern part of the species range in Georgia and Florida.

The pattern was curvilinear, however, with most of the variation occurring

in the east. His pattern is only vaguely apparent in the progeny data

of the present study--a high occurred in east Georgia but another high

occurred in the extreme western portion of the species range.

Thorbjornsen (1961) found geographic variation in stomata per m.

in natural stands of loblolly pine. His pattern ws somewhat similar to

Mergen's, frequency tending to be highest in the eastern part of the range.

But the trend was not uniform, the pattern appearing to be somewhat random

eat of the Mississippi river. He also found a rather strong positive

correlation of stcaSta per m. with a drought index, the ratio of May-

August precipitation over average suaer temperature. A check for a

similar relationship was sought in the present data for slash pine, with

no success--if anything there was a slight negative trend. Apparently

the relationship Thorbjornsen found was mainly due to the very low

sumer rainfall west of the Misisissippi being coincident with low stomatal

frequency in that area. If so, the lack of a relationship for slash pine
is not surprising.










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85

Thames (1963), sapling loblolly pine seedlings originating from

areas in Caldwell and Cherokee Counties, Texas, northwest Georgia, and

Crosett, Arkansas, found stomatal frequencies (both stomata per mrm. and

stomata per sq. nm. of needle surface) to be lowest in the two Texas

sources, which agrees with Thorbjornsen's results. Although there were

only two sources east of the Mississippi the two traits showed no

consistent east-vest trend in this region.

Thames (1963) found no significant racial difference in number of

rows of stoata in loblolly pine and this was also found to be true for

provenances of European larch (Larix decidua Mill.) (Gathy, 1959).

Low stomatal frequency a y be an adaptation to xeric conditions as

suggested by Thames (1963). High stmnatal frequency may be associated

with photosynthetic efficiency as found in Ribes by Bjurman (1959).

Number of resin ducts

The number of ducts in parental foliage averaged 6.90 per needle,

ranging froa 2 to 13 among individual needles, and from 3.0 to 10.2

among mother tree means (Table 3). Trees of the densa variety averaged

slightly more ducts than those of the elliottii variety or those in the

transition sone, but the differences attributable to such groupings were

not significant (Table 4). Stands-within-groups was significant but

accounted for only 9 per cent f the variance. The pattern among stand

means was rather intricate, highs occurring in south-central Georgia,

and also along the coasts of Florida (Fig. 29). The low in extreme

southeast Florida agrees with d reported by De Vall (1941b).

The high mother tree compenent (89 per cent) may be largely due to

environmental edification rather than to genetic differences among
















































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87

trees. White and Beals (1963) showed that resin duct frequency in pond

pine (Pinus serotina Michx.) was related to tree age, growth rate, vertical

position in crown, and "crown exposure side." Their findings suggest

further that even the stand variance may be due to environmental modifi-

cation rather than racial effects.

In the progenies the numbers of ducts were uch fever, averaging

2.40 and ranging from o0. to 5.0 aong seedling means (Table 7). Complete

absence of ducts was extremely rare, being found in the sample of two

needles from a single seedling. "Twos" and "threes" were the most common.

Very little of the variation in progenies was associated with groups

or stands, error accounting for most of it (Table 8). The pattern of

variation among stand means was largely random (Fig. 30). These results

do not agree well with those of Mergen (1958), who found that slash

pine seedlings fro the central and northeastern counties of Florida

and southeastern Georgia had the fewest ducts.

The absence of a distinct difference in number of resin ducts in

parental foliage between the varieties of slash pine agrees with Little

and Dorman's (1954) findings, but not entirely with those of others as

indicated in the tabulation below.























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Author elliottii densa

- Numbers of ducts -

De vail (1941a) 3-5 4-9

De Vail (1945) 2-3a 4-9a

Little and Dorman (1954) 2-8b 3-9b

West and Arnola (1956, p. 6) 3-4 5-10

Present study (ranges among 3-10 4-9
mother tree means)

a Resin droplets visible with a hand lens on a cut surface
in this case.

b For natural stands; the authors showed generally fewer ducts
for plantations, whch may have been an a effect.

Thickness of hypoderm

Although the thickness of hypoderm in the parents averaged only

slightly greater in the densa variety than in elliottii the differences

were significant, 37 per cent of the variance being associated with

groups of stands (Tables 3 and 4). The stand means displayed a clinal

pattern, increasing frno north to south, through much of Florida and a

random one in the north (Fig. 31).

In the progenies the results were completely different. Groups and

stands accounted for relatively small (although significant) portions of

the variation, 7 per cent each (Table 8). North Florida progenies had

slightly thicker hypoderms, on the average, than south Florida ones

(Table 7). But the over-all pattern of stand means showed no clear cut

trends, and contained a large element of randomness (Fig. 32).

The outer, thin-walled hypoderm layer was invariably present in both

parent and progeny material. In the parents at least one fairly continuous,







































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92

inner, thick-valled layer we preset. In the pregenies, horver, the

inner "lyer" often oemsisted of sporadic thiek-wlled cells.

Ike results for parent toees agree fairly vll with Dexma and

Little (195I), although the mrait k of the differences they reported

between elliettii (twe, rarely thr layers) and dema (three to four,

rarely two or five) were greater the i f d here (Table 3). This mw

hwve been due to the fact that only current yea's needles were used

in the prm t study. The poorly developed hypodem fond in seedlings

is probably a ag effect. Because of this ea should aot oenelude

that thm variation in thickness of hypedem in mtw trees is net

gEaetic in nature. In a racial variation study vith pederesa pine,

Veidman (1939) did find that geographi difference in this trait were

inherited to a large eteat.

Little and Dorwa (195~), vh studied Caribbem pine as wll -

slash pine, suggested a peeeible tie-in with cllate, thick hypedF r

being assoeeited vith a deemt dry sees for these subtropical ma

trpical pines. In ponderose pine thick hypoder seem to be seeciated

with sevre climtes (WeidLa, 1939).

Diseissien of Individual Trait Variation

At this point the individual trait patterns ad the omyonmts

of vaerice found in the analyses hall be suamrimel, ad the causes

and nature of the patterns sehll be explored frme the genetic standpoint.

Six of the 12 trait stwuAed in the parents ad 11 of the 13 studied

in the progenies showed siificant difference (either at the 5 or the

1 per cent level) mang gr ps of stads. The prevalence of these

difference vuw not surprising stoee they enempn e the whole species




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PAGE 1

GEOGRAPHIC VARIATION IN SLASH PINE {Pinus elliottii Engelm.) By ANTHONY E. SQUILLACE A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA April, 1964

PAGE 2

AGRICULTURAL LIBRARY 'fiiiiii

PAGE 3

ACKItoWLEDGEMENTS The author gratefully acknowledges the assistance of his supervisory committee: Drs. A. T. Wallace (Chairman), W. O.Ash, A. D. Conger, R. E. Goddard, C. M. Kaufman, and G. R. Noggle. Special gratitude is also due the following organizations for assistance in collecting seed and foliar samples used in the study: Buckeye Cellulose Corporation, Foley, Florida; Continental Can Company, Incorporated, Savannah, Georgia; Florida Forest Service; Georgia Forestry Commission; International Paper Company, Baihbridge, Georgia; School of Forestry, University of Florida; South Carolina Commission of Forestry; West Virginia Pulp and Paper Corporation, Georgetown, South Carolina. Statistical computations were done at the University of Florida Computing Center and financed jointly by that unit, the School of Forestry of the University, and the Southeastern Forest Experiment Station. The author is grateful to these organizations and to personnel who helped with the work. In this effort, special thanks are due Mr. John C. Barnes who did most of the programming and Dr. A. E. Brandt for statistical counsel! . Finally, the author is very grateful to the Southeastern Forest Experiment Station for providing facilities, materials, and technical help and to the many persons of the Olustee Naval Stores and Timber Production Laboratory who helped in various ways on the project. ii

PAGE 4

TABLE OF CONTENTS Page LIST OF TABLES iv LIST OF FIGURES v INTRODUCTION 1 REVIEW OF LITERATURE ..... k General ..... k Slash Pine 8 BASIS FOR VARIATION IN SLASH PINE 15 PROCEDURE ...allParental Material • 2k Progeny Material • ..28 Analyses 29 Single varlate analyses 29 Multivariate analysis 35 RESULTS AND DISCUSSION 37 Single Variate Analyses 37 Cone dimensions ............ .. 37 Seed yield £3 Seed weight 1*3 Germlnability and speed of germination k6 Cotyledon number 54 Total height 56 Stem diameter • 63 Needles per fascicle 68 Needle length 72 Fascicle sheath length 75 Stomatal measurements ................... 75 Number of resin ducts . 85 Thickness of hypoderm 89 Discussion of Individual Trait Variation •• 92 Diversity Among Individuals Within Stands 97 Diversity Among Stands 105 Multivariate Analysis .................... 106 Nomenclature! Considerations 117 SUMMARY AND CONCLUSIONS 119 LITERATURE CITED ...... 122 APPENDIX 130 ill

PAGE 5

LIST OF TABLES Table Page 1. Summary of slash pine seed source tests vhich sampled a relatively narrow latitudinal zone 11 2. Summary of slash pine seed source tests vhich sampled a relatively vide latitudinal zone 12 3. Means and ranges of variation for parental data 38 k. Mean squares and estimates of variance components obtained from analyses of variance of parent tree data ... 39 5. Means and ranges of variation for progeny data of Nursery Test 2 ^7 6. Mean squares and estimates of variance components obtained from analyses of variance of progeny data of Nursery Test 2 US 7« Means and ranges of variation for progeny data of Nursery Test 1 57 8. Mean squares and estimates of variance components obtained from analyses of variance of progeny data of Nursery Test 1 . 58 9« Coefficients of variation for parental data — per cent 99 10. Coefficients of variation for progeny data of Nursery Test 1 — per cent 100 11. Coefficients of variation for progeny data of Nursery Test 2 — per cent 101 12. D values (x 10), vith stands arranged in order of decreasing similarity to 8 stands in the north-central region 107 13* Average vithinand betveen-cluster D values (x 10), clusters formed as described in text and arranged in order of decreasing similarity to "North-central (vest)" cluster 3 Ill lU. D values (x 10) for stands in a transect going from stand 24 (north-central region) southvard through the center of Florida to stand kf (south Florida) 116 iv

PAGE 6

LIST OF FIGURES Figure Page 1. Ranges of the two varieties of slash pine and locations of stands sampled • 9 2. Mean January temperatures •••••• 16 3* Average difference between mean maximum and mean minimum temperature (°F.) during months of April through September 17 4. Mean annual precipitation* •••• 19 5. Precipitation from October through May as per cent of mean annual precipitation • 20 6. The sum of precipitation-evaporation ratios for months of February through April •••••• 22 7* The pattern of stand variation in cone length • • • • ko 8. The pattern of stand variation in cone diameter* ....... kl 9* The pattern of stand variation in sound seed yield per cone •••••• * kk 10* The pattern of stand variation in seed weight. * * 1*5 11* The pattern of stand variation in seed germinability k9 12* The pattern of stand variation in speed of seed germination ...•••.•••.• 51 13* The pattern of stand variation in number of cotyledons per seedling* •• ••••• 55 Ik. The pattern of stand variation in heights of seedlings 59 15* One-year-old slash pine seedlings* showing differences in total height and stem diameter* •••••• 6l 16. The pattern of stand variation in stem diameter* ....... 6k 17* The pattern of stand variation in average number of needles per fascicle in parent trees 69

PAGE 7

LIST OF FIGURES (continued ) Figure *£* 18. The pattern of stand variation in average number of needles per fascicle in progenies. ••• 70 19. The pattern of stand variation in needle length in parent trees. ..... ..... 73 20. The pattern of stand variation in needle length in progenies T 1 *21. The pattern of stand variation in fascicle sheath length in parents 16 22. The pattern of stand variation in fascicle sheath length in progenies. 77 23. The pattern of stand variation in number of rovs of stomata per mm. of needle vidth in parents 79 24. The pattern of stand variation in number of rows of stomata per mm. of needle width in progenies 80 25. The pattern of stand variation in number of stomata per mm. of needle length in parents. 81 26. The pattern of stand variation in number of stomata per mm. of needle length in progenies 82 27* The pattern of stand variation in number of stomata per sq. mm. of needle surface in parents 83 28. The pattern of stand variation in number of stomata per sq. urn. of needle surface in progenies 6k 29* The pattern of stand variation in number of resin ducts per needle in parents • 86 30. The pattern of stand variation in number of resin ducts per needle in progenies. •••• 88 31. The pattern of stand variation in number of layers of hypoderm in parents • $0 32. The pattern of stand variation in number of layers of hypoderm in progenies 91 vi

PAGE 8

LIST OF FIGIBfflB (continued) Figure Page 33* Averages of D values between each stand and eight stands within the north-central region, showing the degree of similarity to that region 109 3^» Delineation of clusters of stands for use in determining relationships 113 35* Diagrammatic representation of the approximate degree of similarity among clusters of stands according to average betweencluster D values Ill* vii

PAGE 9

lflTRQDUCUOK When a plant species occurs over a vide geographic range, individuals or populations growing in different localities frequently display differences in one or more traits* This phenotypic variation associated with locality (geographic variation) may he due to environmental or genetic factors, or interactions hetveen them. Environmental differences are a consequence of modifications caused by habitat factors* Genetic variation associated with locality (racial variation), on the other hand, is due to such mechanisms as mutation, natural selection, hybridization, or combinations of these factors. It basically results from the fact that the individuals within populations differ genetically* The genetic heterogeneity between individuals is caused by mutation or hybridisation. It is maintained by Intricate mechanisms inherent in most species, enhancing chances of survival of the species in a constantly changing environment. This genetic variation among individuals is the basis for racial variation. If the localities are characterized by different environments, and if some degree of reproductive isolation is present, racial variation will occur. Plants that are genetically most suited to their particular habitat will survive and reproduce In greater numbers than those not so well endowed. Some degree of reproductive isolation is necessary because If interbreeding occurs randomly throughout a species range, natural selection in a given locality would merely result in a change in the mean of the whole species. In forest trees, sufficient isolation is provided by the limited distance of pollen and seed dispersal.

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2 Although natural selection Is the most Important cause of racial variation, it is believed that such variation nay also result from chance fluctuations in gene frequencies (genetic drift) leading to fixation of genes* Genetic drift is most apt to occur in small, isolated populations and environmental differences need not he present. Geographic variation occurs in characteristic patterns, depending upon the nature of the forces that caused it. Since climatic factors are often important natural selection forces, and since climate often changes gradually over a species range, the pattern of racial variation frequently is continuous or clinal. However, relatively uniform and discontinuous habitats may cause relatively discrete populations or ecotypes. Likewise, present or past Isolation may cause ecotypes or combinations of both clinal and ecotypic variation. Needless to say, geographic variation In forest trees is common, and it is of great interest to forest land managers and forest scientists. The nature of geographic variation (i.e., the proportion of environmental and genetic components) Is important to land managers because if differences in economically important traits are genetic they must use care in selecting sources of seed for forest planting. Likewise, forest geneticists are keenly aware of the possibilities of capitalising on racial variation in development of superior strains. Taxonomists are interested in patterns of variation in their attempts to classify trees on both the species and subspecies level. The present study was designed mainly to Investigate the nature and patterns of geographic and racial variation for a number of characteristics in slash pine (Pinus elliottil Kngelm.), one of the

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3 more important commercial trees of the Southeast* Secondary objectives were (l) to search for causes of patterns of variation that sight he found, and (2) to compare the magnitude of variation associated with localities against that associated with individuals within localities*

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REVIEW OF LITERATURE General It is probably safe to say that Geographic variation has been studied in all commercially important forest tree species and in many of the noncommercial. ly Important ones, Langlet (1938) summarized much of the early work. Several recent publications include brief reviews of much of the past literature: Dorman (1952), Critchfield (1957) , Echols (195=3), Squillace and Bingham (1958), Callahan (19^2), and Langlet (1963). These studies liave demonstrated that racial variation is prevalent in forest trees, although some species such as red pine (?. resinosa Ait.) shoved no, or relatively small, variation in some traits (Bucliman and Buchman, 1962; and Wright et al., 19^3) • As might be expected, differences were found to be greatest, or most prevalent, where the species range covered a lar^e geographic area, such as ponderosa pine (P. ponderosa Laws.) and Scotch pine (P. sylvestris L.). However, variation lias been found even in trees having a relatively small geographic range, such as sand pine (P. clausa (Chapm.) Vasey) (Little and Dorman, 1952a), and western white pine (P, monticola Dougl.) (Squillace and Bingham, 1958)*

PAGE 13

5 Many of the patterns reported contained an element of continuous or clinal variation. Where the variation is a result of gradual changes in climatic or geographic features, and where complete reproductive isolation is absent, one might, of course, expect the variation in plant characteristics to he continuous. Stebbine (1950> P* ^0 expressed the opinion that most species with a continuous range, encompassing changes in latitude or climate, will be found to possess clines for physiological characteristics adapting them to conditions prevailing in various parts of their range* Numerous patterns showing continuous variation associated with rainfall have been reported (Larson, 1977; Thorbjornsen, I96I; Goddard and Strickland, 1962; and Squillace and Silen, 19^2) • Elevational trends were reported by Callaham and Liddlcoet (1961) and Crltchfield (1957). Numerous Instances of gradual changes associated with latitude or length of photqperlod have been found (Langlet, 1936; and Schoenixe and Brown, 1963). One frequently also sees in the literature evidences of ecotypic patterns of variation (for examples, see Wright, 19^4; Pauley and Perry, 195^; Vaarta^a, 195^; Squillace and Bingham, 1958; and Wella, I962) . However, some of these authors used the term broadly, applying it to patterns which are genetic and adaptive but not necessarily discontinuous. Too, there is often some question aa to whether the ecotypic variation occurs exclusive of other types.

PAGE 14

Theoretically, distinct ecotypes vith no element of continuity can occur in a species having ideographical isolation, and in vhich genetic adaptation to a uniform habitat (such as soil or exposure) has occurred. Ilowever, since the habitat vithin a species range or vithin parts of a species range often varies continuously, combinations of patterns are more likely. Thus, it is possible to visualize a situation in vhich a species occurs in geographically isolated groups, vith ecotypic variation occurri among groups as a result of adaptation or genetic drift, or both. But vith the climate varying continuously through the range we could have clinal variation occurring both vithin and between the ecotypes. This may indeed be the situation in some species such as ponderosa pine, in vhich elevational gradients were reported by Callaham and Liddicoet (1961), and in vhich ecotypes were delineated by Wells (1962). In this same species, Squillace and Silen (I962) pointed out apparent clinal variation associated vith climatic variables but acknovledged that likelihood that discontinuities also occurred; irregularities in a clinal pattern were illustrated by Callaham and Hasel (1961). Clausen et aL. (19^8) found clinal trends for height of plant between climatic races of Achillea lanulosa . In Scotch pine, Wright and Baldvin (1957) and Wright and Bull (19°3) delineated broad ecotypes vithin the species range, vhile Langlet (1936) pointed out that clinal variation for certain characteristics occur both vithin and between ecotypes of this species.

PAGE 15

The existence or nonexistence of the two kinds of variation often becomes a natter of degree, with interpretation highly subject to the opinions of the investigator and confused by terminology. It is no wonder that considerable discussion and debate have resulted on this problem (Turesson, 193&; Eaegri, 1937; Langlet, 1936, 1959> and 1963; Kriebel, 1956; and Callaham, 1962). Until more concrete terminology and guidelines for classification are available (if indeed ever) the wise investigator will describe his pattern of variation as best he can without attempting to classify it categorically (Langlet, 19^3) • Another type of variation noted rather frequently in the literature is random variation. Here differences among stands sampled within the species range may be real but exhibit no distinctive geographical trends or patterns such as clines or ecotypes. This type of variation is likely to occur where the species range is discontinuous in the present or had been so at so:ae time in the recent past, as exemplified by the random pattern found in the major portion of the range of European black pine ( Pinus nigra Arnold) by Wright and Bull (1962) • However, random differences have been found for seed germination in slash pine by Mergen and Hoekstra (195*0 • Likewise, Thorbjornsen (1961) reported random variation for wing length, seed length, cone length, needle length, and frequency of serrations on needle margins in loblolly pine (P. taeda I..). Both of these species have rather continuous ranges. The cause of random variations in such cases is obscure, although partial reproductive isolation which is believed to be common in most trees may have a bearing (Wright, 19^3) •

PAGE 16

8 Slash Pine Slash pine, like many pine species, has suffered a confused nomenclature (Little and Dorman, 195*0 • Recently, these authors (1952b) subdivided it into two varieties, P. elliottii Engelm. var. »niottli, typical slash pine, and P. elliottii var. densa Little and Dorman, South Florida slash pine, formally publishing a description of the latter. The ranges of the two varieties, as given by Little and Dorman (195*0 $ are shown in Figure 1. The authors showed the varieties as being allopatric, the boundary between them being indicated by the heavy dashed line in central Florida. At a later date, Lengdon (1963) published a revised range of the densa variety, extending It northward a considerable distance as shown by the dotted line in Figure 1. He indicated that trees of both varieties occur in the area of overlap. Slash pine does not extend into the Caribbean Islands. Features which, according to Little and Dorman (195*0, distinguish the two varieties are as follows: Var * elliottii ; Needles in fascicles of two and three, and normal seedlings with erect, slender, pencillike stems. Var. densa : Needles in fascicles of two (infrequently three); seedling with grasslike, almost stemless stage with many crowded needles, and thick tap root. The wood of this variety is also heavier and has thicker cummerwood than the typical variety. Mature trees of the two varieties also differ somewhat in general appearance. Variety d ensa is normally shorter, with its stem often forking into large branches and Its crown "being generally flat-topped and open, compared to the usually taller and relatively narrowcrowned typical variety. However, according to many foresters, these differences

PAGE 18

10 and even the more distinctive seedling characteristics become obscure in the portions of the species range where the two varieties meet, making it difficult or impossible to separate the two varieties. Slash pine, being relatively susceptible to fire injury, was originally confined to ponds, pond margins, and other wet areas (Cooper, 1957). With the advent of white man and fire protection it has invaded drier areas, where it grows sympatrically with the relatively fire resistant longleaf pine (P. palustris Mill. ) . South Florida slash pine occurs In pure stands on flatwoods sites in the southern part of its range, while to the north it is confined to the wetter sites along streams and in other poorly drained or swampy areas (Langdon, 19^3)* In the southern portion of its range, there is some degree of geographic isolation between the two coastal areas, caused by the Everglades. The two "prongs" along the coast, however, meet in Polk and Osceola Counties. A number of seed source studies (studies in which seeds were collected from trees growing in different portions of the species range and planted in a common environment) have been conducted with slash pine. Some of these sampled only the northern portion of the species range (Table l), while others sampled a relatively broad latitudinal zone (Table 2). The studies were designed mainly to determine variation within the range of elliottli only. However, sampling in some studies of the latter group (Table 2) extended as far south as Polk County, Florida, which is in the area bordering the two varieties (transition zone). In the "Florida-Georgia" experiment (Table 2), a single source well within the range of denaa (Collier County, Florida) was included

PAGE 19

1 £ 25 a •H U ID a H "J to o 1 3 i •3 o P 1 5 8 *P • CO "j s •H CO U O -C P 3 "S P co © o O •H P ctj o rd H M Q en O nJ en o CM & H P P E CO 0) •H P n a* -: •J ••; i 0) 3 CO 01 CO -p in a) P O a ^ o O CD _ a 3 a) *-. :: H I H co 5 •H O u o

PAGE 20

12 P Tt «M P to . 0) >tf o H O o u CQ 5 1 O 3 § P CO $ 1 § •H o o H 8 o t 3 OJ l/\ •H O H H ltn G O P a O CO Ih CJ cy •H H cO -P 3 +? CO c (0 8 n 5 P (0 tH CO !M O O i^y to o o > C3 (!) I f. Cu o o CC 1 e p 10 10 p o 3 00 r? & 4) 0) CO CO ^

PAGE 21

13 along with elUcttii sources in one of the seven plantations in the test, out vac not included in the statistical tests indicated. As seen in Tables 1 and 2, significant differences vere found more frequently in those studies sampling a broad latitudinal zone than in those sampling only the northern part of the species range. This was especially true for growth rate. In one experiment, latitudinal growth rate differences were mainly due to a sample from Polk County, Florida, in the transition zone and results suggested the existence of natural hybridization between varieties in that area (Mergen, 195^, and Wakeley, 1959). (For further evidences of hybridization see Mergen, 1958.) In still another experiment, growth rate was usually moderately superior among sources from extreme south Georgia and north Florida ( north-central region ), and it decreased both to the north and south of this area (Squillace and Kraus, 1959) • These authors suggested that climatic conditions may be optimum in the north-central region, where superior growth rate may have resulted from relatively strong natural selection for this trait. Resistance to cold damage in the northern fringe and unfavorable distribution of rainfall in the southern areas may have been relatively more important than growth rate in natural selection in these areas* The results for survival were similar to those for growth ratedifferences were found more frequently when a broad latitudinal zone was sampled than when only the northern portion of the species range was sampled. In both the "Southwide" and the "Florida-Georgia" studies early survival was usually greater among northern sources than among southern ones. Some traits, such as stomatal xrequency (Mergen, 1958)

PAGE 22

I* and fusiform rust resistance (Henry, 1959) * showed evidences of longitudinal variation in the north* Several studies other than seed source tests, have also provided Information on geographic variation in slash pine. A plantation near Gainesville. Florida, containing clones from phenotypically superior trees selected in various portions of the range of elllottii (Perry and Wang, 1955) shoved differences in gum yielding ability at about 7 years of age (Anonymous, 19&2, p* 12U). A cattle damage test in south Florida, comparing the two varieties of slash pine, shoved significant differences in growth and survival (Hilmon, et al., 1962). Stemvood specific gravity and/or sunmerwood per cent were studied in elllottii trees growing In their natural habitats by several investigators (Larson, 1957; Perry and Wang, 1958; Wheeler and Mitchell, 1959 and I962; and Goddard and Strickland, 1962). These studies agreed In shoving that specific gravity and summerwood per cent Increase in going from north to south through Georgia and Florida, and from west to east through the northern portion of the species range. The cllnal pattern of variation was shown to be closely associated with seasonal distribution of rainfall, in addition to latitude and longitude. However, the two experiments reported upon by Echols (i960), shown In Table 1, suggest that the pattern in these wood properties is largely environmental rather than genetic. Variation In time of pollen and seed ripening has been reported by Dorman and Barber (1956) • As noted earlier, the above studies dealt mainly with variety elllottii . The possibility of variation within variety dense seems to have escaped study.

PAGE 23

BASIS FOB VARIATION IH SLASH PIHE This section contains an examination of the environmental factors "Which may have been instrumental in causing geographic and/or racial variation to he reported. Information on climate was freely drawn from U.S. Weather Bureau reports (Weather Bureau, 1956 and 1959) • Climate within the range of slash pine varies from a ssone of transition between temperate and subtropical conditions in the north to tropical conditions in the Florida Keys. Temperature variation and other factors are strongly affected by latitude and proximity to the Atlantic Ocean or Gulf of Mexico. Summers are relatively long, warm, and humid; winters are relatively mild due to the southerly latitude and warm adjacent sea waters, but periodically cool and cold air from the north invades the region. Mean January temperatures increase gradually from a low of about 50°F. at the northern extreme in South Carolina to a high of about 70°F. in the Florida Keys (Fig. 2). Ho such gradient occurs in summer, however, mean July temperatures averaging about 80°-82°F. throughout the region. Length of frost-free season increases from a low of about 240 days at the northern extremes to a high of 3^5 days in south Florida. The spread between daily maximum and minimum temperature is greatly affected by proximity to the sea, especially during the growing season. For example, the mean spread for the months of April through September varies from as little as 1^°F. along the coasts to as high as 26°F. in interior portions of the species range (Fig. 3)« 15

PAGE 24

16

PAGE 25

17

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18 Mean annuel precipitation varies from as high as 6k inches in southeast Florida and southern Louisiana and Mississippi, to as low as kh inches at the northern limits in east Georgia (Pig. k)» Although the pattern is Bonevhat erratic there is a general tendency for decreasing rainfall from southern Louisiana, east and northeast to South Carolina, and from south Florida northward. Seasonal distribution of rainfall shows distinctive patterns. Precipitation is distributed favorably In the northern portion of the species range, with highs occurring generally in February and March, and July and August. In the south, most of the total rainfall occurs in the midsummer months and wintertime drouths are rather common. The variation expressed in these terms produces continuous patterns, These are well illustrated in maps drawn by SqulUace and Kraus (1959) which show patterns of rainfall for January through April, and June through September. The same situation is also expressed in Figure 5 which shows isograms for rainfall from October through May as a per cent of annual. Note that it is low in extreme southwest Florida and increases rather uniformly to the north and northwest. Estimates of precipitation-evaporation (P-E) ratios were determined for weather stations within the range of slash pine, using the method described by Thornthwalte (1931.) These ratios are measures of precipitation effectiveness and are estimated from mean monthly precipitation and mean monthly temperature, utiliting Thornthwaite's formula or his nomogram. (The latter, a graphical method, was used for the present study) • P-E ratios were determined for months of February, March, and April, and sunned. These months were chosen because effective rainfall during this period may be more closely

PAGE 27

19

PAGE 28

20 fc

PAGE 29

21 associated with growth of slash pine than rainfall during other periods, as reported by Coile (1936). The data showed a distinctive, continuous pattern (Fig. 6), much like that for October-May precipitation per cent. Hurricanes are caramon along the coastal areas (Weather Bureau, 1959)* Chances of hurricane force winds are greatest at the southern tip of Florida, and the probabilities generally decrease to the north along the Atlantic coast to southeast Georgia where they increase slightly. On the Gulf coast, probabilities decrease northward to the Tampa region but then become high again in west Florida and south Alabama. Soils within the range of slash pine are for the most part sandy in texture, and low in mineral nutrients and moisture holding capacity. They are often underlain with hardpans 18 to 24 inches below the surface. Coastal areas are low and flat while the interior portions are generally rolling, with gentle h 1.1,1 e and ridges mostly under 200 feet in elevation but reaching as high as 3>v5 feet in Florida, and 600 feet in Georgia. local variations in soil characteristics, frequently associated with small differences in elevation (as little as several feet), are common. These variations strongly affect tree growth (Cooper, 1957). Forest geneticists are concerned as to whether or not racial differences associated with local variations in soils are present. Edaphic races have been reported for some species of plants (Snaydon and Bradshaw, 1961) . «bst workers feel that this type of variation has not developed in slash pine. Until recently, slash pine occurred only on pond margins. Natural selection probably has not had sufficient time to cause appreciable changes in gene frequencies on the higher areas, especially since these areas frequently are interspersed with flatwoods.

PAGE 30

22

PAGE 31

23 Geological changes during the Pleistocene period (beginning about 3/4 million years ago) undoubtedly had some bearing on the development of variation in slash pine* Following the Kansan gleciation, the Florida peninsula was reduced to a group of small islands extending from Hamilton County in the north to as far as Highlands County in the south (MacNeil, 1950). The second shoreline recognized by MacNeil, following the Illinoian glaciation, shows a similar group of islands but they were larger and the mainland extended as far south as Alachua County. During the midWisconsin glacial recession, much of Florida occurred as part of the mainland, the peninsula extending as far south as Glades County, with a number of islands mostly along the east and southwest coasts. The final and most recent shoreline recognized by MacHeil was of post-Wisconsin origin. Although the degree of inundation was relatively small at this time, a number of islands occurred along coastal regions.

PAGE 32

PROCKDURK Parental Material The conventional seed source technique was used for this study but with the additional features of: (1) sampling parental materials to measure geographic variation, and (2) maintaining individual mother tree Identity in order to study mother tree variation within stands* In the fall of i960, mature cones and foliage samples were collected from each of five (in a few instances less) mother trees at each of 55 stands scattered throughout the range of slash pine. Proposed stand locations were predesignated mainly by gridding the area on a map, with a spacing interval of about 50 miles. However, irregularity of the species range, non-forested areas, and other considerations necessitated moving many of the proposed locations so that the actual distribution of the stands only faintly resembles a grid (Fig. 1). It should be noted that systematic sampling of stands leads to a bias in variance and the magnitude of this bias is unknown. An alternative procedure would have been to sample stands completely at random or to stratify and sample randomly within strata. Systematic sampling was chosen because of a strong desire to include the extremities of the range, and because it was felt that this method would be most suitable for elucidating patterns of variation. Materials were collected through the aid of cooperators. Instructions included selection of accessible, natural stands as near as feasible to the predesignated points, with the requirements that they (l) be at least too feet away from flowering slash pine plantations, (2) be of fruiting age, and (3) not be selected for any particular traits* 24

PAGE 33

25 Within each stand, mother trees -were selected randomly hut with restrictions that (l) they be dominants or codominants, possessing mature cones, (2) they be at least 200 but not more than 1,300 feet apart, and (3) they have one or more neighbors within 100 feet. In those areas where the two varieties meet or overlap (transition zone), no attempt was made to select one or the other variety, because (l) identification of the varieties in the mature stage is difficult, as noted earlier, and (2) it was felt that attempted selection would prevent the possibility of determining the population structure of the transition zone* Mother trees within stands were designated "A" through "E". These letters, combined with stand numbers (l through 55), served to identify all mother trees. From each tree, 10 to 15 cones and 5 branch shoots were collected from the upper and outer portions of the crowns. Most of the materials were obtained by shooting them out of the trees with a rifle* Plant materials were sent to Olustee, Florida, for processing* Collections were highly successful but, upon receipt of the materials, the sample from stand 51 was found to be loblolly pine rather than slash pine (identification was verified upon sowing of seed). Hence, this stand was discarded. Also, materials for three mother trees (29E, kQk, and 48C) were missing. Finally, it was later determined that mother tree 21D was apparently a hybrid (or backcross) between slash and longleaf pines, and hence data from this tree were eliminated from analyses. These circumstances reduced the number of stands to 54, and mother trees to 266*

PAGE 34

26 In the late fall of i960, after cone collection, seven additional stands were designated (numbers 56 through 62) and used for collection of foliage samples (see Fig. 1 for location of these). These supplementary samples were taken mainly to check on what appeared to he unusual results from the main samples and to increase sampling intensity in north Florida. Data from the supplemental samples were not used in statistical analyses hut were included with data from main samples in elucidating patterns of variation. Upon receipt, the unopened cones were counted and 10 (or less when a shortage occurred) were selected from each mother tree and photographed. The negatives were then projected on a microfilm reader and the lengths and diameters (across broadest portion) of each cone were measured. Cones were dried in the open air; then the seeds were extracted and winnowed with e seed blower which removed practically all empty seed. Full seed were then counted, weighed, and stored in a refrigerator at approximately 'K)°F. until planted. Branch shoots were handled as follows: Eight fascicles were taken randomly from the central portion of the first flush of the i960 increment of each branch shoot (ho fascicles per mother tree). The number of needles per fascicle was determined on each of these. Then 3 fascicles were selected randomly from each group of 8 samples (15 per mother tree), and on these the lengths of fascicles and the lengths of the fascicle sheaths were measured. Finally, 2 additional needles were selected from each shoot, again from the central portion of the first i960 flush of growth (10 per mother tree) and the uppermost 2 Inches of each was cut and preserved in formalin-aceto-ethyl alcohol fluid.

PAGE 35

27 The preserved needle specimens were then used for additional measurements as follows: The lower l/8-inch of each section was cut and examined under a binocular dissecting microscope (h%) and the following measurements taken: (1) Width of the needle, measured across the flat surface or surfaces (binate needles had one flat surface while ternate needles had two), using an eyepiece micrometer; (2) the number of rows of stomata on the flat surface or surfaces; and (3) the number of stomata in two rows, each 1.68 millimeters long (the length of the micrometer scale); for binate needles the second row nearest each edge of the single flat surface was used, while for ternate needles the second row nearest the rounded surface was taken from each of the two flat surfaces. The number of rows of stomata was divided by the total flat surface width in millimeters to obtain "number of rows per millimeter of width." The number of rows per mm. of width was then multiplied by number of stomata per mm. of row to obtain number of stomata per square mm. of needle surface. Freehand cross sections were then cut from the lower end of each of five needle segments (one per shoot) and mounted in water on microscopic slides. These were then examined under a microscope (100X) and the number of resin ducts and number of layers of hypodermal cells determined. The latter measurement proved difficult. Invariably there was a well defined, thin-walled, outer layer of cells. Inside of it occurred one or more "layers" of thick -walled cells, but these were not always in true layers, the innermost frequently containing sporadic, single cells. However, four points were systematically predeslgnated on each section (always between stomata) and the number of "layers" counted at each, to obtain an average for the needle.

PAGE 36

28 Progeny Material Seeds were sown on March lU-15, 1961, In a nursery at Olustee, Florida, in two nursery tests. Nursery Test 1 was designed to obtain maximum development of foliage, and for this reason seeds were sown in plastic pots 6 inches in diameter and 6 inches deep. The design was a randomised block type, with individual tree plots and five replications. Prom one to three seeds were sown per pot, depending upon the number available, and the seedlings were thinned to one per pot soon after germination. Nursery Test 2 was designed mainly to produce seedlings in quantity for outplanting, which is not encompassed In this report. However, the material provided an opportunity to obtain more reliable data on seed germination and cotyledon number than could be obtained from Nursery Test 1 and hence was used for this purpose. In Nursery Test 2, seeds of each mother tree were sown in row plots of Uk seeds each, with 3 replications. But in order to minimise competition effects, the five mother trees of each stand were randomised within stand plots, and stand plots were randomised within replications. Seeds were sown at a spacing of 1 inch within rows and rows were spaced 6 Inches apart. Germination was counted in Nursery Test 2 on March 29, 1961, and again on April 10, 1961. The first count divided by the second count, z 100, gave an index of the speed or rate of germination in per cent, while the latter count (expressed in per cent of seeds sown) alone was used as a measure of germlnability. Also, cotyledon counts were obtained on up to 10 randomly chosen seedlings per row in April, 1961.

PAGE 37

Total heights and stem diameter outside bark at ground line vere measured on the Beer) lings of Nursery Test 1 on November 3, I961. In the late fall of I96I, foliar samples and measurements vere obtained from the potted seedlings of Nursery Test 1 as follows: First, counts of the number of needles per fascicle were obtained on each of 10 fascicles taken from each seedling. Fascicles were chosen randomly from the upper portion of the first flush of growth. The foliar material was then handled in a manner similar to that from the parents. However, here fascicle length and fascicle sheath lengths were measured on three fascicles obtained from each seedling and the stomatal, resin duct, and hypoderm measurements were obtained for two needles per seedling. Analyses Single variate analyses Statistical analyses consisted mostly of two types, single variate and multivariate. In the single variate analyses the stands were divided into three groups as follows: Group 1. Stands within the range of the elliottii variety, excluding those close to the limits of the densa variety, as follows: Numbers 1 through 26, 31 through ho, 52, 5h, and 55. Total, 39. Group 2. Stands arbitrarily considered to be within the transition zone between the two varieties: Nuribers 29, 30, kl, k2, Uh, and h$. Total, 6. Group 3* Stands within the range of South Florida slash pine as delineated by Little and Dorman (195*0 * Numbers 27, 28, U3, 46 through 50, and 53* Total, 9.

PAGE 38

30 Note that the assignment of borderline stands in the transition zone appears inconsistent in some instances, according to limits of the varietal ranges shown in Figure 1. The reason for this is that the assignment of stands into groups vas made according to the smallscale map in Little and Dorman (195^)» the most recent available range map at the time. The northern limits of var. dense shown in Figure 1 were reproduced from Langdon's (19&3) aore recent and detailed map, revealing what appears to be inconsistencies. The purpose of grouping the stands vas to provide a means for determining the presence or absence of significant stand differences within varieties. To this extent, limitations imposed by the arbitrary nature of the grouping should be recognized*

PAGE 39

31 The analyses of variance for data from parent tree samples vere as follows; Source of Variation P.F. Expected Mean Squares 2 2 2Groups of stands (G) 2 "^M + k 12 ^S + k H m 2 2. Stands within groups (S) 51 0"^ + k^ cr i 2. Mother trees within stands (m) 209 o^j Total 262 In the above analyses the deficiency in degrees of freedom for mother trees was due to seven "missing" trees (9B, 21D, 29E, 36B, 48A, 48B, and 48c). Tree 21D was dropped because of evidence that it was a hybrid, while the remaining missing trees were due to lack of samples. Coefficients for the variance con3>onents for all analyses of variance were computed using the technique outlined by Gates end Shiue (1962). For the parent tree analyses the coefficients were as follows: k l2 4.870 1m m 56.464 kgg « 4.869

PAGE 40

32 The analyses of variance for progeny data of Nursery Test 1 were as follows: Source of Variation P.P. Expected Mean Squares Replications (B) k 2 2. 2 2 Groups of stands (0) 2 cr£ + kjo C^ + kj^ ^ • k ll °~G 2. 2 Z Stands within groups (S) 51 °1b + 1*23 C^u ^22 ^ Mother trees within stands (M) 209 ^ * koo ^ Error (E) 1043 0^ Total 1309 In the above analyses the deficiencies in degrees of freedom for mother trees and error were due to seven "missing" mother trees (21D, 22E, 295, 42B, 42P, 48A, and 48c) and five "missing" seedlings (7A-4, 9C-4, 38D-I, 46C-4, and 46P-4) . Mother tree 21D was dropped for reasons noted earlier, while the remaining missing items were due to lack of samples* Coefficients computed for the components of variance estimates, were as follows: k l3 « 4.982 k 12 23-746 k u • 277.504 k 23 a 4.984 kgg m 24.278 k 33 . 4.980

PAGE 41

33 The analyses of variance for progeny data of Kursery Test 2 were as follows : Source of Variation D»F. Expected Mean Squares Replications (R) 2 2 2 2 Groups of stands (G) 2 crz + k^ °~s + ^11 °~G 2 2 Stands within groups (S) 51 ^g. + k 22 °~i A 2 Error 1 (E x ) 106 ff^ Mother trees within stands (M) 202 <^ k 3 3 cr^ 2 Error 2 (E 2 ) 1*04 ff^ Total 767 In the above analyses the deficiency in degrees of freedom for mother trees was due to Ik "missing" mother trees (17D, 21D, 22E, 2$D, 29A, 29C, 29E, 33C, kl£, kSk, U8B, h8c, 53k, and 53C) . Mother tree 21D was dropped for reasons noted earlier while the remaining trees were dropped because of lack of samples. Coefficients computed for the components of variance estimates for progeny data of Nursery Test 2 were as follows: kj^ 14.061 ku = 159-lto k22 14.223 k 3 3 m 3»000

PAGE 42

3* The main purpose ef the analyses ef variance was to obtain objective estimates of the degree of variation associated with the factors studied. To aid in doing this, estimates of components of variance were obtained using the mean squares computed in the analyses of variance and the "expected mean squares" shown above (Snedecor, 1956, p. 26l). The estimated components obtained in this manner were finally expressed in per cent of the total of all components (excluding the "replication" component in progeny data). The component of variance associated with groups was considered to be expressive of the division of the species into the two varieties and the transition zone. That associated with stands within groups expresses the degree of geographic variation within varieties. These two components taken together are expressive of geographic variation for the species as a whole. If either or both of these components were statistically significant and appreciable In magnitude, isograms were drawn in an attempt to elucidate the pattern ef geographic variation for the trait concerned. Bote that the above analyses assume homogeneous variances. As will later be seen, variation was frequently found to be greater in some portions of the species range than in others. This circumstance affects the validity of the estimates of variance components and the significance teats. Hence, the estimates and tests should be considered as approximations.

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35 Multivariate analysis Multivariate analysis was employed to examine the pattern of geographic variation considering a groin) of traits simultaneously. Mahalanobis' "generalised distance function" vas chosen. (For discussions of this and other multivariate techniques see Rao, 1952; Howell, I960; Veils, 1962; Wright and Bull, 19&; and Namtoong, 1963. ) This function, D , expresses the degree of relationship between two populations, considering simultaneously the group of traits chosen. The formula for two traits (x^ and Xg is as follows: in which Xjjl and X^ are the means of trait 1 for the first and second populations, respectively; X21 and X22 "the means of trait 2 for the same two populations; S^ and Sg the pooled estimates of the variances of traits 1 and 2; and S^ the covariance of traits 1 and 2. As can he seen, the magnitude of Vr for any two populations Increases with increasing difference In the means for each trait, and decreases with increasing variance and covariance within populations. For more than two traits the formula is more conveniently expressed as follows: D^« Z Z S " X d d i J II 1 J where d i B tiie mean population difference for trait i and a > the mean population difference for the jth variable J -1 and 8^ , m the element in the inverse of the covariance matrix corresponding to the 1th and Jth variable.

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36 Using procedures outlined by Rao (1952, pp. 3^5 and 357), D 2 values were confuted for 17 traits, including k from the parent tree data (cone length, cone diameter, seeds per cone, and seed weight), and 13 from progeny data (total height, stem diameter, number of temate fascicles, needle length, sheath length, revs of stomata, stomata per mm*, stomata per sq. mm*, resin ducts, hypoderm thickness, gendnahillty, speed of germination, and cotyledon number). Since there were 5k stands or "populations" a total of (5*Q (53) 1*^31 values of D 2 had to he computed. 2 The work was done with an IBM 709 electronic computer at the University of Florida Computing Center.

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RESULTS AND DISCUSSION Results of the single vallate analyses and patterns of variation for individual traits vlll be presented first* Following will be a recapitulation of the individual trait patterns along with a discussion of possible causes of variation. Next will be an analysis of the degree of variation (diversity) among Individuals within stands and among stands within varieties and their implications. Then follows the results of the multivariate analysis, and finally a discussion of taxonomic considerations. Single Variate Analyses Cone dimensions Mother tree means of cone length varied from 7*0 to 15*5 cm. (Table 3) • Host of the variation was associated with mother trees within stands but stands within groups accounted for a considerable proportion (22 per cent) of it (Table k). Since little of the variation was associated with groups of stands (6 per cent) the trait was not distinctive for varieties. The stand-to -stand variation exhibited a fairly distinctive pattern, however. Cones were relatively short in southeast Florida and increased to the north (Fig. 7)* An east-west maximum occurred near the Georgia-Florida boundary (Walton County. Florida, to Duval County. Florida), above which cone length decreased slightly. Variance components for cone diameter were rather similar to those for cone length, with stands accounting for a sizable proportion (37 per cent) and with groupings of stands accounting for none of it. Although the variation among stands was not associated with varieties. a fluctuating clinal pattern was apparent (Fig. 8) . Cones were thickest 37

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-.. 38 ! 5 5-p to a P< o to H SB,<5

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39 jj

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ko m u o •p o LU

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kl

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4 2 in the collection from Collier County, Florida, and they decreased in diameter toward the north, east, and south. An east-vest trough seemed to occur in the neighborhood of Polk County, Florida, and another extending southwest-northeast through the northern portion of the species range, with a mini mum at Brantley County, Georgia. The cone dimensions found here (Table 3) agree fairly well with values reported by others, as seen by the tabulation of "common" ranges below* However, it is obvious that these cone dimensions are not particularly useful for identifying varieties. Authors elliottii densa Both varieties Small (1933# P« 4) 8-12 Coker and Totten (1937, p. 19) Little and Dorman (195*0 9-14 Wakeley (1954, p. 198) West and Arnold (195$, p. 5-6) 8-11 Ward (1963) Present study (ranges among 8*2-1 mother tree means) Little and Dorman (1954) 4-5 Wakeley (1954, p. 198) Present study (ranges among 3.1-5.3 mother tree means) Lengthcentimeters 8-15 7-12 8-15 6-14 6-15 — m*

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h3 Seed yield Seed yield was extremely variable both among mother trees (l to 127 seeds per cone) and among stands (3 to 97 seeds per cone) (Table 3 and Fig* 9) • Much of the variation among mother trees was associated vith groups (22 per cent) and stands vithin groups (32 per cent) (Table h). Variation among stand means fell into an irregular dinal pattern (Fig. 9)* Soma of the irregularity may be due to differences in stand density or similar factors not studied. A high occurred in an area centering at Thomas County, Georgia* vith a moderately high ridge extending to the east and vest* Yield usually decreased from this ridge both to the north and south, reaching an extremely low point at Big Pine Key, Florida* Since seed crops generally vary from year to year, and since locality by year Interactions are probable (Tourney and Korstian, 1S&2, p* 105), one should not assume that the pattern of seed yield per cone found here would be consistent in time* The mean sound seed yield found for the whole species, 51 seeds per cone, is lower than that reported by Wakeley (195*0, 60-70 seeds per cone* The discrepancy may be due to yearly effects as noted above, or to differences in the degree of winnowing* Seed weight The means of seed weight for mother trees were extremely variable (10 to 51 mg. per seed) (Table 3) . Much of this variation was associated with stands and it exhibited a clear, mostly clinal pattern (Table h and Fig. 10). A northeast-southwest trough occurred In southeast Georgia extending from Pierce County to Evans County. Seed weight increased in

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Uh

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45

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k6 all directions from this area. To the south, a northeast -southwest high occurred extending from Dixie County, Florida, to Duval County, Florida* It then decreased Irregularly to the south, note that the rate of change, however, was not uniform, the drop being the sharpest in south Florida. The mean seed weight for all trees, 30. 6 mg. (which converts to about 14,800 seeds per lb.) agrees well with the ranges for slash pine given in the Forest Service Woody Plant Seed Manual (Anonymous, 1°A8# p. 269), 13,000 to 16,000 seeds per lb. and also with the ranges of the means of 100-seed samples, 2.8-3.5 grams, given by Wakeley (195^, p. 198). Germlnabillty and speed of germination Germlnability of seed varied highly among mother trees (6 to 100 per cent) (Table 5) • Significant amounts of the variation were associated with stands and groups (17 and 6 per cent, respectively) (Table 6) • Germlnability averaged highest in the densa variety, next highest in the transition zone, and lowest in the typical variety. However, the pattern seemed to contain a large element of randomness and no lsograms were drawn (Fig. 11). The results agree with Mergen and Hoekstra's (195*0 • in that significant differences among seed lots from different portions of the range of the typical variety were found and that no distinctive pattern occurred. However, the differences in germlnability of seed from comparable areas in the two studies showed little agreement. Germlnabillty of seed may of course be affected by maturity at time of collection and other factors. Although attempts were made to collect only mature cones, there is no assurance that all lots were of the same degree of maturity. Hence, even though significant stand

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Table 5.— Means and ranges of variation for progeny data of Nursery Test 2 47 Group Germinability" Per cent Speed of germination 13 Per cent Cotyledons Number MEANS 1 2 3 All groups 60.7 66.7 73*2 63.3 67.1 75.3 89.4 71.4 7.43 7.29 6.83 7.32 RANGES AMONG SEEDLINGS 1 2 3 1 2 3 RANGES AMONG MOTHER TREE MEANS 6-96 23-9^ 14-100 0-99 7-100 53-100 4-12 4-13 4-10 6.0-9.4 6.2-9.3 5.5-8.0 sowing. b Per cent of sound seed germinating vithln 27 days after 15-day germination 100 27-day germination

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kS Table 6.— Mean squares and estimates off variance components Obtained from analyses off variance off progeny data off Nursery Test 2 Germinahility Speed off germination Cotyledons

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^9 » ».

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differences vere found they were not necessarily genetic in nature. Speed of germination also varied greatly among mother trees (from to 100 per cent) (Table 5). Significant proportions of the variation vere accounted for by groups and stands (13 and 9 per cent, respectively) (Table 6). The stand variation exhibited a distinctive clinal pattern (Fig. 12) • A lov occurred in Ware County, Georgia, which also tended to extend westward to Holmes County, Florida, and Catalina Island, Mississippi, and northeastward to Georgetown County, South Carolina, as well. Speed of germination Increased both to the north and to the south of the trough. Evidence of racial variation in speed of germination has also been found in lodgepcle pine (P. contorta Dougl.)(Critchfield, 1957) $ eastern hemlock ( Tsuga canadensis (L.) Carr.) (Stearns and Olson, 1958), spruce ( Picea ) (Schell, i960) , and ponderosa pine (Callaham, 1959 «nd 1962). Like germinability, differences in maturity of seed could have had some effect upon the differences In speed of germination among stands. However, the nature and distinctiveness of the trends practically rule out the possibility that such extraneous factors could have caused the pattern. More likely it was due to genetic differences in the seeds, brought about by natural selection and causing differential response to environmental stimuli. It is of interest to speculate on the nature of the genetic differences that were apparently present, and on the particular environmental factors to which the seeds responded at the planting site. Past studies suggest that temperature is a major environmental factor. According to Callaham (1962), the speed of germination of tree seeds is

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51

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52 governed primarily by tender ature, given adequate moisture and light, with germination proceeding most rapidly at some optimum temperature. Experiments by Jones (1961) suggest that photoperiod was not a predominant factor in causing the differences in rate of germination. He shoved that a single exposure of slash pine seeds to 15 minutes of daylight doubled the total germination per cent over that obtained under complete darkness. But illumination periods of 8-, 12-, and 16-hours caused no differences in either speed of germination or total germination per cent. Assuming that temperature was a major environmental factor, one might speculate that the seeds possessed different genetically-fixed optimum temperatures and this would be reflected in different rates of germination when the seeds were planted in a common environment. Such was found to be the case through laboratory tests by Callaham (1959 and I962) for ponder© s a pine. However, this alone would not explain why seeds brought north from south Florida and south from the northern limits to Olustee, Florida, germinated early* Presence or absence of seed dormancy may have been important. In examining this possibility, it is well to review what is known about factors that may be involved. Most slash pine seed are shed In October (Cooper, 1957)* Under natural conditions, seed tend to germinate In spring, but when soil moisture is adequate considerable germination may occur in early autumn (Derr, 1959)* la south Florida, conditions for early fall germination would seem to occur rather frequently because October rainfall there averages about 6 Inches. In contrast, October rainfall averages about 2 Inches in the north. In the south, the winter months are dry (average rain about 2 inches per month) and relatively warm, while in the north they are wetter (about k inches per month) and considerably cooler.

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53 Stored slash pine seeds show a mild degree of dormancy, germination being abetted by stratification, vhile fresh seed do not (Anonymous, 1S&8) • These findings on dormancy were most likely based upon work with the typical variety of slash, although this point is not certain. It is possible that dormancy may be more characteristic of northern seeds than southern seeds. In the north, if the seeds do not germinate promptly in the fall, there would likely have to be a mechanism built into the seeds to prevent germination over winter, because of the danger of cold temperatures to newly germinated seedlings* In the south, on the other hand, there would not seem to be a need for dormancy, because of the warm winters. In fact, it would seem that germination as early as possible after seed fall would carry a high selective advantageprompt germination to avoid mortality from severe winter drouths. The fact that northern seeds will germinate promptly under favorable conditions in the fall suggests that onset of dormancy (if it actually occurs) is delayed. Prompt fall germination undoubtedly carries a high selective advantage— trees germinating in the fall obtaining "a head start" cm those germinating in the spring in regenerating denuded lands. However, prompt fall germination under suitable weather conditions plus dormancy when weather conditions fail would seem to be the best combination for the variety. These conjectures on dormancy are feasible in view of the findings with several forage species in Europe, in which it was shown that germination characteristics of species inhabiting different climates were closely tied in with dormancy mechanisms (Cooper, 1963) •

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54 Assuming both differential dormancy and different optimum temperature requirements, we might attempt to explain the results of the present study. South Florida seeds germinated earliest because they lacked dormancy. Seeds from south Georgia and north Florida germinated late because the stored seed possessed a mild degree of dormancy— had the seed been stratified differences may not have been found. Seeds from the extreme northern limits of the species range germinated promptly because, although they also may possess moderate dormancy, their optimum temperature vas attained sooner, having been moved from a northerly to southerly direction. The latter conjecture assumes no difference in optimum temperature requirements vlthln the northern region. Of course these are little more than guesses, further experimentation being necessary on this problem. Cotyledon number The number of cotyledons per seedling varied from as low as k to as high as 13 (Table 5) • Much of the variation vas associated with stands (24 per cent) and groups of 6tands (17 per cent). Stand averages displayed a distinctive cllnal pattern (Fig. 13) much like that for seed weight (Fig. 10). On the average, cotyledon numbers were higher in the north than in the south (Table 5). However, as seen In Figure 13, the pattern is much more subtle than this, with a low occurring in the north as well as in the south. The means and ranges agree fairly well with previously reported values, as indicated in the following tabulation (means are followed by ranges In parentheses).

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55

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56 Both Author elliottll dense varieties . . Numbers of cotyledons Engelmann (2.880, pp. nk, 186)* 8(6-9) b Butts and Buchhols (19*0) 7.73(5-10) b Little and Doxman (195^) DeSoto Rational Forest, Miss. 7.36(6-9) Clinch County, G*. 7.72(5-10) Hendry County, PI*. 6.76(5-8) Present study (ranges are 7.^3(^12) 6.83(^-10) 7.32(^-13) among seedlings) a Cited by Little and Doxman (195*0 b Origin not specified The correlation between cotyledon number and seed weight on a stand mean basis was .72, highly significant) the pooled correlation for mother trees within stands was .42, also highly significant. Racial variation in respect to cotyledon number has also been found in loblolly pine (Thorb jornsen,196l) • The positive correlation between seed weight and cotyledon number agrees with findings by Buchholz (19*6) for ponderosa pine. Total height One-year-old seedling heights varied greatly and the majority of the variation (66 per cent) was associated with groupings of the stands. Seedlings in the northern portion of the species range were tallest (Tables 7 and 8, and Figs. Ik and 15). Variation in the north was relatively small but heights decreased rapidly going from north to south through Florida. Thus, the pattern is largely random in the north and cllnal through Florida. There was also a modest east-west gradient

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Figure 15.— One-year-old slash pine seedlings, shoving differences in total height and stent diameter. Upper photo represents a latitudinal transect through the species range, the one on the extreme left being from Big Pine Key, Florida, and the one on the extreme right from Sumter County, Georgia* Lower photo shows differences between trees from the west coast (the two trees on left), the interior (center two), and the east coast (the two on right) of central Florida.

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61 WVWttWim 53^5 %te 2tfl>3 ZlbS 2#V< I Z^A-5 IR-t)-l \Vb-5 ?0*/Y5 W-5

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62 through central Florida, seedlings being tallest in the center of the state, and shortest along the coasts. In a general way these results are in harmony with Little and Dormsn's (195^) use of stem height as a diagnostic feature for identifying varieties* However, because of the gradient in Florida it apparently would be difficult to classify seedlings in the transition zone. The fact that seedlings in the north-central region were not particularly taller than those at the extremities of the north, seems to disagree with findings by Squillace and Kraus (1959) • However, seeds were relatively small and germination relatively late in the north-central region. These two factors apparently had some effect upon heights. The wi thin-stand pooled correlation coefficient between seedling height and seed weight was .31 (significant at the 1 per cent level) and between seedling height and rate of germination, .17 (significant at the 5 per cent level). On the other hand, the superiority in early height growth of trees from the north to those of the south is great enough to be real in spite of seed weight and rate of germination effects. Reasons for this difference probably lie in the fact that the south generally suffers from extremes of climatic and other environmental conditions more so than does the north. Such factors could Include poor rainfall distribution with frequent droughts in spring and flooding in summer, damaging tropical storms, and possibly frequency of fires. In the south, natural selection is probably relatively strong for resistance to these factors, which may cause relatively weaker selection for rapid growth than in the north.

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63 Admittedly there ere also climatic extremes In the peripheral portions of the north* For example, relatively oold temperatures and frequent ice storms are characteristic of the area just south of the northern limits; tropical storms are relatively frequent along the Gulf coast; rainfall distribution is relatively unfavorable along the coasts of Georgia and South Carolina; conditions conducive to fusiform rust damage seem to be most favorable at the northern ex tr e mi ties (McCulley, 1950). The east-vest gradient through much of Florida may be associated with the difference between mean maximum and mean minimum dally temperatures (Fig* 3)— trees tend to be tall where the temperature difference is relatively high* This possible association is supported by findings reported by Kramer (195?) and Hellmers (1962)— In laboratory tests loblolly pine and northern red oak ( Quercus rubra L.) grew fastest under the greatest day-night temperature differential tested* Stem diameter Variation in stem diameter showed a moderately high racial component (25 per cent for groups and 6 per cent for stands within groups) and the stand means exhibited a clinal pattern (Table 8 and Fig. 16). Stems were thickest in the South Florida seedlings and they decreased rather uniformly to a northeast-southwest low extending from Taylor County, Florida, to Liberty County, Georgia* Forth of this trough, diameters Increased slightly, but were not as large as those from south Florida* Stems usually were thicker (especially relative to height) along the coasts of Florida than In the Interior. Thick stems are an indication of a carrot-like taproot. Thus, In a general way, the results agree with Little and Dorsum's (195*0 use of

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6k

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65 this trait as a diagnostic feature. Stands in groups 1, 2, and 3, averaged 7.1, 7.k, and 8*5 cm., respectively. Trees from stands near the northern limits of the species range had moderately thick stems but they were taller than South Florida seedlings and hence vould not detract from diagnostic utility of this trait. However, like total height, the difficulty is that because of the clinal nature of the pattern it vould apparently be difficult to classify trees or stands in the transition cone. Thickness of stem in slash pine seedlings has undoubtedly been Important in natural selection. South Florida seedlings, which characteristically have thick stems, are more resistant to fires than north Florida seedlings (Ketcham and Bethune, 1963)* Apparently, this thickening of the hypocotyl, which is mostly dead outer bark but also inner bark and wood, Imparts a degree of Insulation against heat (Little and Dorman, 195*0 • The thick stem also probably provides a means for storing food, utllisable for sprouting when the crown burns. Hence, the trait is assumed to have resulted as an adaptive response to fire (Little and Dorman, 195**0 • If the trait is an adaptive response to fire, one would expect that the frequency of natural fires, or the extent of damage from fires, increases gradually from north to south, following the pattern of variation In stem thickness. No concrete and reliable data could be found to check this possibility. However, as noted earlier, slash pines in the north were originally restricted to ponds, pond margins, and other wet areas. Hence, it is possible that fires in the south Invaded slash pine stands more frequently, and perhaps were more intense, than in the north. Extended

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66 late winter and early spring drouths and high winter temperatures, common in the south, may he factors affecting the frequency and intensity of fires. Regressions were calculated to determine factors that might have been involved in the apparent natural selection on stem diameter. Stem diameter (stand means in centimeters, Fig. 16) was used as the dependent variable. Independent variables used were as follows: (1) latitude (stand values in degrees); (2) the sum of precipitationevaporation (P-R) ratios for months of February through April (stand values, Fir. 6); and (3) mean January temperature (stand values in °F., Fig. 2). P-R ratios (used as a measure of late winter-early spring drouth) and January temperature were considered as possible environmental factors causing natural selection. Latitude in itself could not, of course, cause natural selection, but the variable was included to test the apparently strong latitudinal trend and to see if effects of P-S ratios and temperature, independent of latitude, could be shown. The analyses included simple, multiple, and curvilinear regressions. Results are shown below. Simple Regression Analyses Coefficients of Stem diameter (Y) on : Regression coefficients determination Per cent Latitude (X x ) -.0232 1»0.1»* Feb.^Apr. P-B ratios (X 2 ) —00V2 15.6»* Jan. temperature (X 3 ) .0090 36. T**

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67 Multiple and Curvilinear Analyses Stem diameter (Y) on:

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68 From the analysis we can only conclude that the latitudinal trend in stem diameter, with a reversal in the north-central area, vas significant. Temperature and P-B ratio may hare had some real association with the trend, but some other environmental factor must also be involved. Weedles per fascicle Both binate and ternate fascicles were found in the parental samples, but the relative frequencies varied considerably as indicated by average numbers of needles per fascicle (Table 3). Stand differences displayed a very distinctive pattern, with a north-south high in extreme southeast Georgia and northeast Florida, and another northwest-southeast high in north-central Florida (Fig. 17) * Needles per fascicle usually decreased gradually away from these highs. A notable feature was that, although numbers were low in south Florida, they were also usually low at the extremities of the species range. Thus, the results do not agree well with Little and Dorman's (1954) recommended use of this character for separating varieties— differences in sampling technique may have caused the disagreement. Average number of needles per fascicle in the progenies was generally higher than in the parents (Table 7). This may be due to an effect of tree age, or to the fact that the progenies, being grown in a nursery, had a more favorable environment than trees under natural conditions. A very few progeny fascicles contained four needles and one contained five. The pattern of variation among stands In the progenies was somewhat similar to that in the parents (Fig. 18). However, the two pronounced highs found in the parents were less noticeable in the progenies and also the difference between south Florida and the remainder of the species range was more pronounced in the progenies.

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69

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TO

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71 The pattern of variation in both parents and progenies seems to be, in some respects, associated with severity of environment. The low in south Florida coincides with unfavorable distribution of rainfall and the low in the extreme north is associated with cold winter temperatures. Somewhat similar trends have been reported for ponderosa pine. Needles per fascicle in ponderosa pine tend to be low in eastern portions of the species range (Weidman, 1939; Haller, 19^2; and Wells, 1962), where the climate is relatively severe and the trees are generally slower growing. The results agree with Shaw's (191*0 statement that in some species of trees the number of needles per fascicle is dependent upon climatic conditions, smaller numbers occurring in colder regions. The apparent relation of needles per fascicle and severity of climate may be associated with photo synthetic efficiency. It can be shown that a ternate fascicle has about 20 per cent more leaf surface area per unit of needle volume than a binate fascicle of the same diameter and length. Thus, a ternate fascicle, having more surface area for absorption of light and for exchange of gases per unit of chlorophyll-bearing tissue, may be more efficient photosynthetically than a binate one. A binate type, on the other hand, would seem to be an adaptation for conserving moisture loss or for frost hardiness, at the expense of growth efficiency. High frequency of ternate fascicles then may be an adaptation to vigorous growth in optimum climate while a tendency toward a preponderance of binate ones an adaptation to less favorable climate. These possibilities would seem to be worthy of further study.

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72 Heedle length Needle length In the parent trees exhibited a rather complicated pattern of variation among stands (Fig. 19). In general, needles averaged longer within the range of variety dansa than in the north (Table 3). However, the tendency was not uniform, highs occurring in the north as well as in the south. Needles tended to be relatively long in the coastal areas, suggesting a possible tie-in with the difference between mean minimum-mean maximum temperatures (Fig. 3). But the correlation coefficient between these two variables was nonsignificant (r • -.23). The pattern in the progenies was simpler, containing a strong element of clinal variation (Fig. 20). Needles were generally long in south Florida (excepting at the extreme tip) and they decreased northward to a northeast -southwest lov through south Georgia, and then increased above this area. The pattern vaguely resembles that in the parents in that needles were, on the average, longest in the south (Table 7). The ranges in lengths of needles for parent material are compared against those shown by others below. Author Harlow (1931) Small (1933* p. h) Coker and Totten (1937# p. 19) West and Arnold (1956, p. 5-6) Present study (ranges among mother tree means) a Rarely, 10-25

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73 Si
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7h

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75 Fascicle sheath length Variation in fascicle sheath length in the parental data was strongly associated with stands, none of it "being associated with groups (Table h). But the pattern of stand variation was rather intricate (Fig. 21). A significant feature was that a pronounced north-south low occurred through the center of Florida and southeast Georgia. In the progenies the stand component of variation was significant hut rather small, 11 per cent (Table 8) . Stand means displayed no particular trends, with a large element of randomness (Fig. 22) • The ranges of variation in sheath length found in the parental data do not agree very well with reports hy others as seen below. The discrepancies may be due to differences in maturity of the foliage sampled, or to differences in technique of measurement (such as inclusion or exclusion of frayed ends). Authors elliottii densa Centimeters De Vail (19*aa) O.8-I.3 1.0-1.4 West and Arnold (1956, p. 5-6) 1.3 *nd under 1.6 Present study (ranges are among 1.2-2.3 1.1-2.3 mother tree means) De Vail (19^0) considered fascicle sheath length to be very diagnostic, it being unaffected by climate, soil type, tree age, etc., and that the character was useful to separate slash and longleaf pine. Stomatal measurements Results of the three measures of stomatal frequency were similar in that (l) in the parental data only small amounts of variance were associated

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76

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77

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73 with groups or stands, with the patterns of the stand means being largely random; and (2) in the progenies it was possible to show patterns for the stand means, although they were somewhat erratic (Figs. 23 through 28). A common feature was a tendency for 6tomatal frequency (all three types of measurements) to average relatively high in the north and low in the south, and also some tendency for a high to occur in the north-central area. Mergen (1958) found a dinal pattern for stomata per mm. increasing from west to east in slash pine progenies from 12 sources encompassing much of the northern part of the species range in Georgia and Florida. The pattern was curvilinear, however, with most of the variation occurring in the east. His pattern is only vaguely apparent in the progeny data of the present study—a high occurred in east Georgia but another high occurred in the extreme western portion of the species range. Thorbjornsen (19^1) found geographic variation in stomata per mm. in natural stands of loblolly pine. His pattern was somewhat similar to Mergen' s, frequency tending to be highest in the eastern part of the range. But the trend was not uniform, the pattern appearing to be somewhat random east of the Mississippi river. He also found a rather strong positive correlation of stomata per mm. with a drought index, the ratio of MayAugust precipitation over average summer temperature. A check for a similar relationship was sought in the present data for slash pine, with no success— if anything there was a slight negative trend. Apparently the relationship Thorb jornsen found was mainly due to the very low summer rainfall west of the Mississippi being coincident with low stomatal frequency in that area. If so, the lack of a relationship for slash pine is not surprising.

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8k 00 D 1 CM to CO u P-4

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85 Thames (1963), sampling loblolly pine seedlings originating from areas in Caldwell and Cherokee Counties, Texas, northwest Georgia, and Crosett, Arkansas, found stomatal frequencies (both stomata per mm. and stomata per sq. mm. of needle surface) to be lowest in the two Texas sources, which agrees with Thorbjornsen's results. Although there were only two sources east of the Mississippi the two traits showed no consistent east-west trend in this region. Thames (I963) found no significant racial difference in number of rows of stomata in loblolly pine and this was also found to be true for provenances of European larch ( Larix decidua Mill.) (Gathy, 1959)* Low stomatal frequency may be an adaptation to xeric conditions as suggested by Thames (19^3) • High stcmatal frequency may be associated with photosynthetic efficiency as found in Ribes by Bjurman (1959) • Number of resin ducts The number of ducts in parental foliage averaged 6.9O per needle, ranging from 2 to 13 among individual needles, and from 3.0 to 10.2 among mother tree means (Table 3)« Trees of the densa variety averaged slightly more ducts than those of the elliottii variety or those in the transition zone, but the differences attributable to such groupings were not significant (Table U). Stands-wi thin-groups was significant but accounted for only 9 per cent of the variance. The pattern among stand means was rather intricate, highs occurring in south-central Georgia, and also along the coasts of Florida (Fig. 29). The low in extreme southeast Florida agrees with data reported by De Vail (19*Hb) . The high mother tree component (89 per cent) may be largely due to environmental modification rather than to genetic differences among

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86

PAGE 95

87 trees. White and Beals (1963) showed that resin duct frequency in pon^ pine ( Pinus serotina Michx.) was related to tree age, growth rate, vertical position in crown, and "crown exposure side." Their findings suggest further that even the stand variance may be due to environmental modification rather than racial effects. In the progenies the numbers of ducts were much fewer, averaging 2.k0 and ranging from 0.0 to 5.0 among seedling means (Table 7). Complete absence of ducts was extremely rare, being found in the sample of two needles from a single seedling. "Twos" and "threes" were the most common. Very little of the variation in progenies was associated with groups or stands, error accounting for most of it (Table 8). The pattern of variation among stand means was largely random (Fig. 30). These results do not agree well with those of Mergen (1958)* who found that slash pine seedlings from the central and northeastern counties of Florida and southeastern Georgia had the fewest ducts. The absence of a distinct difference in number of resin ducts in parental foliage between the varieties of slash pine agrees with Little and Dorman's (195*0 findings, but not entirely with those of others as indicated in the tabulation below.

PAGE 96

88

PAGE 97

89 Author elliottii densa . Numbers of ducts De Vail (l^la) 3-5 *-9 De Vail (19^5) 2-3* fc-9* Little and Dorman (195*0 2-8 b 3-9 b West and Arnold (1956, p. 6) 3-k 5-10 Present study (ranges among 3-1° *•*§ mother tree means) a Resin droplets visible with a hand lens on a cut surface in this case. b For natural stands; the authors showed generally fewer ducts for plantations, which may have been an age effect. Thickness of hypoderm Although the thickness of hypoderm in the parents averaged only slightly greater in the densa variety than in elliottii the differences were significant, 37 per cent of the variance being associated with groups of stands (Tables 3 and h) • The stand means displayed a clinal pattern, increasing from north to south, through much of Florida and a random one in the north (Fig. 31) • In the progenies the results were completely different. Groups and stands accounted for relatively small (although significant) portions of the variation, 7 per cent each (Table 8). North Florida progenies had slightly thicker hypoderms, on the average, than south Florida ones (Table 7) • But the over-all pattern of stand means showed no clear cut trends, and contained a large element of randomness (Fig. 32) « The outer, thin-walled hypoderm layer was invariably present in both parent and progeny material. In the parents at least one fairly continuous,

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90

PAGE 99

91 P-4

PAGE 100

92 inner, thick-walled layer was present. In the progenies, however, the inner "layer" often consisted of sporadic thick-walled cells. The results for parent trees agree fairly veil with Dorman and Little (195*0, although the magnitude of the differences they reported between elliottii (two, rarely three layers) and dense (three to four, rarely two or five) were greater than found here (Table 3). This may have been due to the fact that only current year's needles were used in the present study. The poorly developed hypodexm found in seedlings Is probably an age effect. Because of this one should not conclude that the variation in thickness of hypodexm In mature trees is not genetic in nature. In a racial variation study with ponderosa pine, Heidman (1939) did find that geographic differences in this trait were inherited to a large extent. Little and Dorsum (1954), who studied Caribbean pine as well as slash pine, suggested a possible tie-in with climate, thick hypodexm being associated with a dormant dry season for these subtropical and tropical pines. In ponderosa pine thick hypodexm seems to be associated with severe climates (Weidman, 1939)Discussion of Individual Trait Variation At this point the individual trait patterns and the components of variance found in the analyses shall be summarized, and the causes and nature of the patterns shall be explored from the genetic standpoint. Six of the 12 traits studied in the parents and 11 of the 13 studied in the progenies showed significant differences (either at the 5 or the 1 per cent level) among groups of stands. The prevalence of these differences was not surprising since they encompassed the whole species

PAGE 101

93 range and in seme instances reflect varietal differences. However, 10 of the 12 parental traits and 12 of the 13 progeny traits studied showed significant differences among stands within groups. Thus, geographic variation (both phenotypic, as evidenced by parental traits and genetic, as evidenced by progeny traits) seems to be the rule rather than the exception in slash pine, even when considering the varieties as separate taxonomic entities. In some traits, variation associated with location of the stands was relatively high and in others it was low. Here we are considering variation over the whole species range, which is expressed by the magnitude of the group and stands-within-groups components of variation, taken together. In the parents, this total stand-to-stand variation was relatively high for cone dimensions, seed yield and weight, needles per fascicle, needle length, sheath length, and hypoderm thickness; it was relatively weak or absent for stomatal measurements and resin ducts. In the progenies, total stand-to-stand variation was high for total height, stem diameter, needles per fascicle, needle length, speed of germination, and cotyledon number, while such variation was relatively weak for sheath length, stomatal measurements, resin ducts, and hypoderm thickness. Germinability also showed strong differences associated with locality of source but variation, in this case, may not have been genetic. The patterns of stand-to-stand variation differed among traits but most of them showed continuity in one form or another. Seven of the traits showed clear, clinal trends with a single distinct reversal: cone length, seed yield, and seed weight in the parents; speed of germination, cotyledon number, stem diameter, and needles per fascicle in the progenies.

PAGE 102

Nine others also showed continuity, but the trends vere rather highly fluctuating and sometimes intricate, with two or more reversals: cone diameter, needles per fascicle, needle length, fascicle sheath length, and resin duct6 in parents; needle length, rows of stomata, stomata per mm., and stomata per sq. mm. in progenies. Two traits showed a random pattern in the north and a clinal trend in the south: hypoderm thickness in parents and total height in progenies. Five showed statistically significant differences among groups and/or among stands within groups hut no distinct geographic trends or ecotypes were apparent: rows of stomata and stomata per mm. in parents; germinabllity, fascicle sheath length, and hypoderm thickness in progenies. Finally, two showed no significant stand differences: stomata per sq. mm. in parents and resin ducts in progenies. As was also indicated above, the patterns contained reversals, where clinal trends changed direction. These were evidenced by definite "highs" or "lows" within interior portions of the species range. In approximately half of the traits a reversal occurred in the north-central region. Some traits showed several clearly defined reversals. Since clinal trends were associated with these, and since this type of variation likely results from adaptation to continuous environmental factors, the reversals were taken to be indications that two or more environmental factors were involved in causing the pattern and that interactions and/or curvilinear effects occurred. For example, winter temperatures may have a strong effect on a particular trait in the extreme north, with only a weak effect in the south. The opposite could be true for winter precipitation and if both of these factors affected a single trait a reversal could occur.

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95 It is pertinent at this point to consider the nature of the clinal patterns from the genetic standpoint. Natural selection operates on individual traits, and, in doing so, it changes the gene frequencies at the loci involved. Different selection pressures in different portions of the species range then may cause differences in gene frequencies (Dobzhansky, 1951> P» 176). Thus, considering a particular trait, a clinal pattern may be viewed as a gradient in frequencies of the gene or genes affecting that trait. As a result of the gradient in gene frequencies there will he a similar gradient in genotypic frequencies. In other words, although it may sometimes be convenient to consider a cline as a gradually changing "t/pe tree," it is more realistic to consider it as a gradual change in the proportion of the different possible types of individuals. Of course, if the trait under consideration is affected by a number of genes and/or if environmental effects occur, various intergrades may be found. A consequence of this situation is that unless complete fixation, or "loss of genes," has occurred in one or more areas, one can expect to find deviant individuals in all parts of the species range. An example seems to be available in slash pine— Perry and Wang (1957) found that about k per cent of seedlings in a South Florida slash pine nursery bed did not show a "grass stage" and that various intergrades were present. If the interpretation of a cline, based on a gradient in gene frequencies, is correct then one should be cautious in speculating on the origin of deviants— they may frequently be just as much a part of the population in the area found as are normal seedlings.

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96 The magnitude of genetic variation among trees within stands vs. that due to stand location is of particular interest to tree improvement workers— the comparison is important in judging the relative merits of within stand and "between stand selection. The parental data are of little value in considering this question because the estimated components of variance contain environmental effects along with genetic ones and the two kinds cannot be separated. The progeny data, on the other hand, can be used to study the question posed, excepting where maternal effects (nongenetic effects associated with maternal parents and due to maternal half-sibs having a more uniform environment than progenies not so related) are present. Maternal effects are probably not great in trees except where the trait is related to morphological and physiological factors of the seed. Thus, in the progeny data, germinability, speed of germination, and cotyledon number likely contain maternal effects and this is evidenced by the fact that the mother tree component for these was unusually large in comparison to error. The maternal effect in cotyledon number is due to the strong relation of this factor with seed weight. Seedling height and stem diameter possibly contain small maternal effects because of their relatively weak association with seed weight. The remaining progeny traits likely contain no maternal effects. For the reasons discussed above only the progeny data of Table 8 should he considered in comparing wi thin-stand vs. between stand variation. In the 10 traits of Table 8 the mother tree component of variance was usually not greatly different from the stand-wi thin-group component. In four of the traits the mother tree component was much less than the group

PAGE 105

97 component. Thus, even if one considers the varieties as separate taxonomic entities, genetic variation within stands was usually not much greater than standtostand variation. The data suggest that genetic gains are feasible through selection among stands as well as among individuals within stands in slash pine. Diversity Among Individuals Within Stands The degree of variation among trees within stands is of interest in determining the genetic structure of the transition zone. If the two varieties are actually distinct and occur sympatrlcally within the transition zone, one would expect the variation among mother trees within stands to he greater in that area than elsewhere. This is so because mother trees were selected at random with no consideration of varietal differences (which, in any event, are not distinct in mature trees). If introgressive hybridization has occurred (recently enough to still be apparent) one would not only expect greater variation amoug mother trees but also among seedlings within progenies. In order to study this problem, coefficients of variation (C*s) were computed as outlined below: 1. In the parental data variances were computed among mother tree means within stands (5 or less per stand), for each trait, and C's were obtained from these (making 3k C's for each of 12 traits). 2. In the progeny data of Nursery Test 1, two kinds of C's were obtained: a. C's were computed among mother tree means within stands (5 or less per stand) as in "1" above (5^ C's for each of 10 traits). b. Variances were computed among the five (or less) seedlings of each progeny (mother tree) and then pooled for each stand, and C's were computed therefrom. Thus, each C here was based upon 25 or less seedlings and there were 5^ C's for each of 10 traits.

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98 3» In the progeny data of Nursery Test 2, C's were computed among mother tree means as in "1" above (5U C's for each of 3 traits). Pooled, within group averages of the C's outlined above were then obtained in order to compare the magnitude of diversity among elllottii, transition, and densa stands. Results are shown in Tables 9 (lower part), 10 (central and lower parts), and 11 (lower part). Contrary to expectation, C's were not generally highest in the transition zone. In some cases the group averages differed little, while in others large differences occurred. In two of them, germinability and speed of germination (Table 11), average C's were high in elliottil stands and low in transition stands. But on the whole there was a tendency for these measures of variation to be highest in densa stands, intermediate in transition stands, and lowest in the elliottil stands. This is apparent in the following tabulation, showing the numbers of average C's for each group classified according to their relative magnitude. (For stomata per mm. of length in parental data, where groups 1 and 2 had equal averages, a value of l/2 was entered in both "highest" and "intermediate" classes; a similar procedure was followed in other cases where group averages were equal.) Group Highest Intermediate Lowest 1

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1 I 1 £ s 5 5 V I ON 2 •3 a co £3 I n'i u • A i jt iaco I r• • • to ft h If II a> o . * # . ,. « , to 111 « w 1, 0) « o co p, o o k 5 c 1 fO^tIA IA CO LA CVJ I CO • • • I • CO LA 0\| CO \0 Hb-| Jt • • • I • mvo la | ia t-t-O I ON • • • I • coco.^ I co ONCOCVJ I IA • • • ] • fO-dco| .=! H40I ON • • • I 4 t>CMA J CO O OCO I ON O VO tA OO CVJ • • * COVO t^ LA LA H W CO • • • CVJ l>fc t-vo ON • • tt cola la O HCO • • • LAO ON H O •-( H I * • t-OMA CO H « H -4" ON -3& as rl CVfOH H CVJ H J| [*• • • I • IA 0\ON | VO LAHCO I ON • • • I • lAOjfr I LA H CJ H I H lALACO | H • • • I q onco j o VOVO H LA • • • I • vOvOVO I VO CO t^LA J t*• • • I • CO b-C0 I CO CVJ nO -=*• t VO • • • l • CO ONO\ | CO 99 HvO-sf • • • COCO H CO ONCJ • • • 0>ONH COVO o ONVO t«LA .St CO • • • co CO co ^r covo • • • CM H CM r-i H rt ON CO O 3 H CO LA CO s a H CVJ COH 3 I 10 I IS •P c to (3 I ! efl

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100 I i I Mil lib S « lit VO OCO • • • vo fOiA H^W.ON t—iAiA I ia CM W t~ • • • POO t• • • W cow torn.* -4CO ON t-tACO VO.SfVO • * • .tfVOVO VO f^ ON HOW • • • lAONON 00 00 H • • • H WOO H W IA o co vo ON w 9 IA ON lACOco • • • onvooo iavo.* • • • t»t-vo COH ON • • • J*J* to O H ON • • • ONVO H COW IA VO t»t^ OniaOn co mo\ • • • cocoh. C\ W IA • • • r4 r4 ri h w m w ON w W IA W 8*31 9 w VO # OHl vo vo t-V0 I vo ON vo * d IA ON ^ 1ACO I H 333 I 4 ONW ON t-ONVO a «* » Woo CO I vo • • • I • CO ON ON I CO t^w. 333 IAIA O w a & Jt ONOO J C • • • \ • 333 3 $8tt W* CJIAO 3^8 w • o w on j M HI I HOIMH to to I 1 E

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101 Table 11.— Coefficients of variation for progeny data of Nursery Test 2— per cent Group Gerninability Speed of germination Cotyledons

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102 A chi -square test of independence vas computed on the data of the above tabulation (Snedecor, 1956* p. 225). The null hypothesis of independence vas rejected (P < .025). But since the average C's were not highest in the transition zone, the results present no evidence of recent hybridization or of the presence of a "mixture" of individuals of the two varieties in the transition zone. In order to examine wi thin-stand diversity more closely, the individual stand C's were plotted on maps as was done for trait values* Diversity was frequently found to be lowest in the north-central region, the coastal area of Georgia, and north-central Florida. It tended to be high in south Florida, and moderately high in central Florida, the west, and the northern fringe area. Speed of germination and genainability were notable exceptions— as expected from the group averages discussed earlier, their patterns were largely opposite to those shown for most traits. It is pertinent at this point to explore the possible causes of the patterns of diversity. The pattern shown by the bulk of the traits shall be considered first. One possibility lies in the existence of islands during the Pleistocene, many of which occurred in Florida. Presumably, many of the islands were very small at times, permitting fixation of genes by genetic drift. Migration following subsidence of the ocean level could then cause a mixing of different genotypes from different islands and from the mainland. This, however, would not explain why the coastal areas of Florida tended to show more diversity than those in the interior. Stands in the coastal areas must have resulted through migration from the interior islands or peninsulas

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103 after each subsidence of the ocean level. Similarly, this gives no explanation for the moderately high diversity in the west and the northern fringe area. Another possibility (not necessarily exclusive) is that high diversity was due to the presence of critical and highly fluctuating environmental factors. As noted earlier, the extremities of the species range are generally characterized by more severe climatic factors than interior portions. In some cases these factors are fluctuating or occur sporadically, such as the alternating drouth and flooding in the south (Langdon, 1958b) , tropical storms in the south and coastal regions, and ice storms in the extreme north. Under such conditions the populations Involved must maintain high diversity in order to survive. That is, they must maintain a variety of genotypes, some well suited to the extremes of the environmental factors and some to normal conditions. The diversity may he maintained by heterozygote preference (balanced polymorphism), as shown by Dobzhanaky (1951# P» 117) in Drosophila populations. Under less critical and/or stable conditions, on the other hand, there is less need for maintaining highly divergent types, with natural selection favoring those most suited to the favorable or stable conditions. Why did speed of germination and germinability show a trend opposite to that for most traits— the tendency for high C's in the north-central area and low ones elsewhere? A reasonable explanation is that strong natural selection for rapid germination has occurred in the south due to prevalence of adequate moisture in October and winter drouth. That is, the selection was probably strong enough to eliminate or greatly reduce the number of types that fail to germinate

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l6k promptly, ahead of the coining vinter and early spring drouthy season, thus causing low -variation in this trait. In the north-central area, on the other hand, maintenance of variability in respect to speed of germination may he most conducive to survival of the population. Here conditions favoring fall germination occur sporadically and there is probably a need for maintaining both dormant and nondormant types. Germlnability may merely be related to speed of germination through pleiotropy, explaining vhy It tended to follow the pattern for speed of germination. The hypothesis suggested by the results is consistent with commonly accepted theory of evolution and speciation in that species are so constituted as to attain a balance between fitness of individuals to the prevailing environment and heterogeneity, providing maximum likelihood of survival of the species as a whole in a changing environment (Dobzhansky, 1951* P« 108, and others). The heterogeneity is provided by mechanisms inherent in the species such as balanced polymorphism and others. It Is only a step further to surmise that the magnitude of the heterogeneity will depend upon intensity of the factors causing it-the severity and degree of fluctuation of environmental conditions, and the nature of the trait (i.e., the degree of its adaptiveness) under consideration . Although the explanations for diversity within stands seem logical, they are actually little more than guesses, further study being needed on this subject*

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105 Diversity Among Stand* Thus far the degree of variation among Individuals within stands has been considered. Another question of interest concerns differences in the degree of variation among stands within portions of the species range. In order to examine this question, coefficients of variation were computed among stand means within the three groupings of stands already described. She data are shown in the upper parts of Tables 9, 10, and 11. The results followed a pattern similar to that for variation within stands— •C's were highest in dense stands, intermediate in transition stands, and lowest in elliottii stands. The pattern is seen more clearly in the following tabulation, showing the numbers of between-stand C's for each group classified according to their relative magnitude. Gro u p Highest Intermediate Lowest 1 H-l/2 6 14-1/2 2 7 10-1/2 7-1/2 3 13-1/2 8-1/2 3 Totals 25 25 25 A cM -square test of independence was computed on the above data and the null hypothesis of independence was rejected (P < .01). What factors might have caused greater variation among stands in the south compared to the north? The fact that individuals within stands in the south were also more variable may have had some effect, since the variation in stand means depends partially upon variance among individuals. However, if the variation among stands was due entirely to variation among individuals, the differences between groups would have been

PAGE 114

106 considerably less. For example, in that case, the stand C's would have been approximately 1 a 0.U5 as great as the mother tree C's, because there were usually five mother trees per stand. Similarly, the stand C's would have been only 1 0.2 as great as the seedling C's because vW there were usually 25 seedlings per progeny. That this was not so is apparent in the data. It is possible that differences in stand variation were due largely to the fact that sampling was less intensive, geographically, in the south than in the north— that is, on the average, stands sampled were furthest apart in the south. Another possibility lies in the existence of islands during the Pleistocene. As noted earlier, these occurred to a greater extent in central and south Florida than in the north. Effects of genetic drift, presuming they occurred, may have then persisted in some degree to the present time. Still another possible explanation is that variation in soils and some climatic factors is greater in the south than in the north. Although concrete data on this comparison is lacking, Harper (1927) stresses the importance of high habitat variation in the ecology of the south. High habitat variation could, of course, cause high genetic diversity among stands through natural selection. Multivariate Analysis Table 12 gives D values obtained from the Mahalanobis' distance function analysis decribed earlier. Note that the tabulated data are the square roots of the distance functions, D 2 , and that they were then multiplied by 10 to eliminate decimals without losing accuracy. The

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PAGE 116

108 magnitude of each indicates the degree of similarity (not necessarily true relationship in the genetic sense) between the respective two stands, taking into account simultaneously the 17 traits used in the analysis. Thus, a relatively low D between two stands indicates a relatively high degree of similarity, while a high one indicates dissimilarity. In general, the results agreed well with results of the single variate analyses. Examination of the D values immediately revealed that D's between stands in the north-central region and those in the south were greatest. In order to examine this point further a group of 8 stands (Nos. Ik, 15, 16, 18, 19, 20, 24, and 3*0 within the northcentral region, which showed a very low wi thin-group average D, were selected* Then the D value between each of the other stands and those eight were averaged to obtain a value indicative of the degree of similarity to stands in the north-central region. For example, for stand no. 1, the D values between stand no. 1 and the 8 selected northcentral stands were 39, 46, 40, 42, 47, 39, 38, and 35 (from Table 12); the average of these is approximately 4l. Comparable averages for the eight north-central stands chosen were also obtained by computing average D values among them. For example, for stand no. 14, the D values between stand no. Ik and the other 7 north-central stands were 26, 29, 24, 26, 36, 30, and 34; the average of these is approximately 29* The average D values, computed in this manner, are shown in Figure 33 (also, in Table 12 the stands are arranged according to the magnitude of these averages). Note that the data in Figure 33 revealed a familiar pattern, with a northsouth clinal trend and a reversal in the north-

PAGE 117

109 CO TJ -H H o * m -P
PAGE 118

110 central region. The gradient ie steep in central Florida. In the vhole northern region an east-vest pattern is also apparent — stands vithin the northcentral region were more closely similar to each other than to those to the east or west. It is important to note that Figure 33 expresses only the similarity of each stand to those in the north-central region. Thus, stands having roughly equal averages are not necessarily closely related to each other, although this is frequently true as will be seen later. In order to examine relationships among stands in various portions of the species range, the "cluster technique" described by Rao (1952) was used. The process began by first selecting pairs of adjacent stands which showed relatively small D values. These pairs formed the nuclei for clusters. Additional stands were added to each, the requirement for acceptance being that the proposed addition does not greatly increase the average D and that it fit better than in other clusters. In forming the clusters it was found that the average D usually increased with the addition of new stands, frequently because of the existence of clinal variation. Thus, the number of clusters formed was highly arbitrary. However, in view of the fact that the main purpose of clustering was to show relationships between clusters rather than to designate ecotypes, the procedure was considered satisfactory. The result of the clustering process is shown in Table 13 • A total of 10 clusters, containing from 1 to 10 stands each, were formed. Note that the wi thin-cluster averages (the value on the extreme right of each row of values) is smaller than the between-cluster averages in each case, which shows the effectiveness of the clustering procedure. With a few

PAGE 119

•3 if O P Pt, i o> u I 4 Is s3 I p 3d B J5 ft) I £ ft) U 3 O P O C ffl £%£ to p" co CO p p a w 1 1 I i CO 0O 1A ffl t W ro ro Fg rj

PAGE 120

112 exceptions, the stands within clusters are contiguous Geographically (Pig. 3^). One of the exceptions is the "Western (coastal)" clusterstand 11, curiously, is widely separated from 5 and 6. The fact that stand Ik fitted better with the "Forth-central (west) " group rather than with the "Northern fringe" was also puzzling. The relatively large withincluster averages for "Central Florida" and "South Florida" are apparently a consequence of high stand-tostand variation noted earlier in the single-variate analyses. The approximate degree of similarity among clusters is shown in Figure 35, which is based upon the data of Table 13. Note that the figure does not show all possible D values and is not drawn to scale accurately— an impossibility with only two dimensions. Nevertheless, clusters appearing close together in the figure are relatively similar, while those far apart are dissimilar. As can be seen, clusters near to each other geographically tend to be relatively similar, largely because of clinal trends. However, note several exceptions. For example, "Northern fringe" is more similar to "Central Florida" (average D between these two clusters 70^ than is "North-central (west)" (average D between "Central Florida" and "North-central (west)"« 77) $ even though "Northern fringe" is furthest from "Central Florida" geographically. The same situation is true for the "Northeast" cluster. This seemingly anomalous situation is apparently a consequence of the trend reversals commonly occurring in the north-central region, pointed out earlier. The "Western (coastal)" and "Northern fringe" clusters curiously hang together and the reason for this is obscure. The "North Florida" cluster is more similar to those in the south than are clusters in the north, as might be expected because of the clinal trends.

PAGE 121

113

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114 North-central (east) North-central (vest) Western North Florida South Florida Western (coastal) Northern fringe Florida Keys Figure 35 • — Diagrammatic representation of the approximate degree of similarity among clusters of stands according to average between-cluster D values . "Northeastern" cluster, not shown above, is very similar to "Western." For average D values not shown above, see Table 13 .

PAGE 123

115 A test for clinal vs. ecotypic variation was made by a procedure similar to that discussed by Wells (1962) and Wright and Bull (1963) • A transect extending from stand 2U in the north-central region southward through the approximate center of Florida to stand kj was delineated. D values between the stands represented on this transect are compiled in Table Ik, Note that D values for geographically contiguous stands (those on the extreme right) are smaller than those to the left (noncontiguous stands), and that they generally increase from right to left within a row or from top to bottom within a column. This shows that contiguous stands are more similar to each other than noncontiguous ones, and that the further two stands are apart geographically the greater is their dissimilarity. The values change relatively more rapidly near the center of the transect than they do at the ends. This is a consequence of the relatively steep gradient in trait values in central Florida, shown earlier, for a number of individual traits. The change in the rate of change in central Florida, however, hardly justifies delineation of ecotypes as the variation is largely clinal to the north, to the south, and across, the central area. Two other transects were formed— one extending from the north-central region southward along the east coast of Florida and the other beginning in the same region and extending southward along the west coast of Florida. The results in both cases were similar to those of Table 1^. In the above analysis, stands in the north-central region were used as starting points to test for latitudinal dines. The reason for tills was that above this area the trends change direction, as shown in Figure 33, and in many of the individual trait patterns. Because of the limited

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116 Table lU. — D values (x 10) for stands In a transect going from stand 24 (north-central region) south-Herd through the center of Florida to stand 47 (south Florida) Stand ; 24 ; 55 .' 31 | 42 ! 44 \ 45 \ 46 * ^7 55

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117 "breadth of the northern fringe area it is difficult to prove a dinal trend with the use of D values hut there is little question that it exists. Observation of Figure 33 and many trait patterns shows that changes northward from the north-central area are usually gradual. The D values show no evidence of an unchanging longitudinal cline in the north. This, however, does not mean that racial variation does not exist in the north, nor does it mean that changes are not gradual. The study of clusters, as weU as the individual trait patterns, showed that longitudinal variation does occur in the north. The pattern, however, is not a simple cline. The clusters delineated in the north could he considered as ecotypes, hut with the qualification that changes "between ecotypes are gradual. Another way to descrihe it might he to say that the longitudinal variation is continuous hut highly fluctuating. nomenclature! Considerations In view of the fact that most of the traits studied showed continuous variation, one may question the division of the species into varieties. The differences "between slash pines in the north and those at the extremes of the species range certainly are striking in several respects and they are genetic to a large extent. It seems proper therefore to ascribe different names to these extreme types. The common name "South Florida slash pine," and even its scientific name, have hecome well accepted and the separation certainly serves a purpose. It is "better, for example, to prescribe silvicultural treatments separately for the two varieties than to prescribe a single treatment for the whole species, or to label seed as "being of one or the other variety rather than to lahel it merely "slash pine."

PAGE 126

118 However, there are those vho feel that subdivision in the presence of clinal variation is misleading and does more harm than good, "because it gives a false impression of homogeneity within the taxonomic subgroups, disguises gradients among subgroups, and discourages study of variation among subgroups (Huxley, 1938; and Langlet, 1959 and I963). This viewpoint certainly has merit. Subdivision also tends to Impart a certain degree of "smugness," causing laxity among both forest managers and researchers. It becomes tempting, for example, to assume that trees at the extreme southern tip of Florida would require exactly the same silvicultural treatment as those in central Florida because they are both South Florida slash pine, while trees ,5ust beyond the "boundary line" require a different treatment because they are of a different "species" (many foresters have actually elevated the subdivision to a species level in their thinking and conversation). Irrespective of nomenclature, one should keep in mind that South Florida slash pine and typical slash pine may not be discrete genetic entities cleanly separated from each other morphologically, physiologically, or geographically; that many traits show clinal variation both within and between the varieties; and that for some purposes, especially (but not limited to) seed collection, it is therefore highly desirable to specify the exact geographic origin of material rather than merely specifying its varietal name.

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SUMMARY AMD CONCLUSIONS The main purpose of this study was to determine patterns of geographic variation for a number of morphological and physiological traits of cones, seeds, foliage, and seedlings in slash pine, and to determine the causes of such variation vhere found. Mature cones and foliage samples were collected from each of 5 trees in 5^ natural stands scattered throughout the species range in the fall of i960. Seeds extracted from the cones were sown in a nursery at Olustee, Florida, in the spring of the following year, and foliage samples were collected from the resulting seedlings in the fall of I96I. Data were taken on 12 traits in the parents and 13 traits in the progenies, and were subjected to analyses of variance to determine the proportions of variance associated with groups of stands, stands within groups, and mother trees within stands. The parental data gave information on phenotypic variation associated with locality while the progeny data, for the most part, gave information on the extent of genetic variation associated with locality of source. Isograms were drawn to elucidate patterns of variation where justified. Regression analyses were employed to study relations with climatic factors. A distance function was used to study a group of traits simultaneously. Major findings and conclusions follow. 1. Most of the traits studied showed significant differences associated with the geographic source of the material. In the parental data such stand-to-stand variation was relatively strong for cone dimensions, seed yield per cone, seed weight, needles per fascicle, needle length, fascicle sheath length, and hypoderm thickness, while it was relatively weak or absent for various measures of stomatal frequency and frequency of resin ducts. In the progeny data, stand variation was strong for total 119

PAGE 128

120 height, stem diameter, needles per fascicle, needle length, gerndnability, speed of germination, and cotyledon number, while it was relatively weak for sheath length, stomatal frequency, resin duct frequency, and hypoderm thickness. 2. Most traits showed some type of dinal or continuous variation, containing one or more trend reversals. The clinal patterns apparently resulted from genetic adaptation to gradients in environmental factors. The trend reversals were probably due to the existence and interaction of two or more factors affecting each trait. Random variation, possibly due to genetic drift, was found in a few instances. 3. Many traits showed a generally northsouth trend through Georgia and Florida with a reversal in the north-central region (extreme south Georgia and north Florida). This general pattern probably resulted from the latutudin&L gradient in winter temperatures (or similar factors) and in seasonal distribution of rainfall. Curvilinearity or interactions of these could be the cause of the reversal. k. Longitudinal variation also existed in the north but was usually not as pronounced as latitudinal variation. The longitudinal pattern for most traits could be described as being continuous but highly fluctuating. 5* Multivariate analysis similarly revealed a latitudinal gradient through Florida and Georgia, which contained a reversal in the northcentral region and which was relatively steep in central Florida. Thus, stands in the north-central region were less similar to those in south Florida than were those in other portions of the north. 6* Variation among trees within stands tended to be least within the north-central region, the coastal area of Georgia, and north-central Florida, and greatest in south Florida and other extremities of the species range. This was believed to be due to the existence of severe environmental factors in the latter group, which probably fluctuate greatly in time, resulting in maintenance of a greater variety of genotypes than in the central areas. 7» Variation among stands tended to be low in the north and high in the south. This may have been partly due to prevalence of islands in Florida during Pleistocene times, causing stand variation through genetic drift, and possibly to higher variation among habitats in the south than in the north. 8. Trees growing within the ranges of the two varieties showed dissimilarity in several respects, but patterns were usually continuous both within and between varieties. No evidence of the existence of two distinct types (representative of varieties) was found within the transition zone. Likewise, no evidence was found to suggest that trees in the transition zone are hybrids between dense and ^1 i 1 ottii varieties. Hybridization and introgression may have occurred during the Pleistccene or earlier but if so, subsequent natural selection has apparently obscured it.

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121 These conclusions were based largely on the fact that diversity among trees within stands was not greatest in the transition area* 9. The sampling design used, although much more intensive than that employed in past slash pine studies, contained several deficiencies. A greater intensity of sampling in central and south Florida would have given a better measure of differences in stand-to-stand variation in different areas. More mother trees per stand and more progenies per mother tree would have given a "better measure of variation within stands, an important consideration in studies of this nature. Finally, it may have been preferable to delineate zones for sampling purposes and select samples randomly within zones. These and other deficiencies of the study should be considered in evaluating its results.

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LITERATURE CITED Anonymous. I9U8. Woody plant seed manual. U.S. Forest Serv. Misc. Pub. Ho. 65^. Ul6 pp. . 1962. Florida Agricultural Experiment Stations, Annual report for the fiscal year ending June 30, I962, P» 12 1 *. Barrett, James P. I962. Relation of relative oleoresln yielding potential to geographic seed source of slash pine. Ph. D. Thesis, Duke Univ. 52 pp. . 1963a. Slash pine gum flow unaffected by seed origin. Forests and People 13(2): 18-19. . 1963b. Slash pine gum flow unaffected by seed origin. Nav. Stores Rev. 73(7): *•!• Bethune, James E. i960. Geographic seed source in connection with fusiform rust of slash pine. Office Rpt., Southeast. Forest Expt. Sta., Asheville, N. C, March 23, I960. 7 pp. Bjurman, B. 1959. The photosynthesis in diploid and tetraplold Ribes satigrum . Physiol. Plantarum 12: I83-I87. Buchhols, John T. 19^6. Volumetric studies of seeds, endosperms, and embryos in Pinus ponderosa during embryonic differentiation. Bot. Gas. 108(2): 232-2WT Buckman, Robert E. and Roland G. Buchman. 1962. Red pine plantation with U8 sources of seed shows little variation in total height at 27 years of age. Lake States Forest Expt. Sta. Tech. Note No. 6l6. 2 pp. Butts, Dorothy, and J. T. Buchhola. 19^0. Cotyledon numbers in conifers. Trans. 111. Acad. Sci. 33: 58-62. Callaham, Robert Z. 1959. Temperature and seed germination for races of ponderosa pine. Proc. 9th Internatl. Bot. Cong. Vol. 2 Abs.: 57-58. . 1962. Geographic variability in growth of forest trees. In "Tree Growth," edited by Theodore T. Kozlowski. Ronald Press Co., New York, pp. 3H-325* , and A. A. Hasel. I96I. Pinus ponderosa : Height growth of wind-pollinated progenies. Silvae Genetica 10: 33-^2. 122

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123 Callaham, R. Z., and A. R. Lid&icoet. I96I. Altitudinal variation at 20 years in ponderosa and Jeffrey pines. Jour. Forestry 59(11): 8ll4~820« Clausen, Jens, David D. Keck, and William M. Hiesey. 19^8. Experimental studies on the nature of species. III. Environmental responses of climatic races of Achillea . Carnegie Inst, of Washington, D.C. Pub. 58I, 129 pp. Coile, T. S. 1936. The effect of rainfall and temperature on the annual radial growth of pine in the southern United States. Ecol. Monog. 6: 533-562. Coker, William Chambers, and Henry Roland Totten. 1937* Trees of the southeastern United States. Univ. north Carolina Press, Chapel Hill. ^17 pp. Cooper, J. P. I963. Species and population differences in climatic response. In "Environmental control of plant growth," edited by L. T. Evans. Academic Press, New York and London, pp. 38l-l»00. Cooper, Robert W. 1957* Silvical characteristics of slash pine. Southeast. Forest Expt. St a. Paper No. 8l: 13 pp. Critchfield, William B. 1957. Geographic variation in Pinus contorta . Maria Moors Cabot Found. Pub. No. 3: lib pp. Derr, Harold J. 1959. Time of year for direct seeding. In "Direct seeding in the South," A symposium. Duke Univ., Durham, N. C. pp. IIU-II9. , and T. R. Dell. i960. Where should ve get slash pine seed for Louisiana? Forests and People 10(2): 30-31. , and Hans Enghardt. I960* Is geographic seed source of slash pine important? South. Lbrmn. 201(2513) : 95-96. De Vail, Wilbur B. 19*»0. A diagnostic taxonomic constant for separating slash and longleaf pines. Proc. Fla. Acad. Sci. 4(1939) : H3-H5* . 19^1a. The taxonomic status of Pinus caribaea Mor. Proc. FTaT Acad. Sci. 5(19^0): 121-132. . 19^-lb. The taxonomic status and ecological variations of certain southern pines. M.S. Thesis, Univ. of Fla., 125 PP» . 19^5 • A bark character for the identification of certain Florida pines. Proc. Fla. Acad. Sci. 7(19^): 101-103. Dobzhausky, Theodosius. 1951« Genetics and the origin of species. Columbia Univ. Press, New York. Third Ed., Revised, 36^ pp.

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124 Dorman, Keith W. 1952. Hereditary variation as the basis for selecting superior forest trees. Southeast. Forest Expt. Sta. Paper So. 15, 88 pp. , and John C. Berber. 1956". Time of flowering and seed ripening in southern pines. Southeast. Forest Expt. Sta. Paper Ho. 72, 13 pp. Echols, Robert M. 1958. Variation in tracheid length and wood density in geographic races of Scotch pine. Yale Univ. School of Forestry Bui. No. 6h, 52 pp. I960. Variation in specific gravity, tracheid dimensions, and proportion of sunmcrwood in slash pine trees from different geographic sources. Unpublished Office Bpt., dated July 26, i960, Southern Forest Expt. Sta. Engelmann, George, i860. Revision of the genus Pinus and description of Pinus ELLiottii. Acad. Sci. St. Louis Trans, k: I6I-I89. Faegri, Knut. 1937» Some fundamental problems of taxonomy and phylogenetics. Bot. Rev. 3: UoO-^23. Gates, Charles E., and Cherng-Jiann Shiue. 1962. The analysis of variance of the S-stage hierarchal classification. Biometrics 18: 529-536. Gathy, P. 1959* Contribution 4 l'etude des races du melere d'Europe ( Lerix decidua Kill.) (The races of L. deeidus ) . Trav. Sta. Rech. Groenendaal (Ser. B) No. 22, 20 pp."" (Seen in Forestry Abs* 22(1): 386). Goddard, R. E., and R. K. Strickland. 1962* Geographic variation in wood specific gravity of slash pine. TAPPI ^5(7): 606-608. Greene, James T. I962. A seed source study of slash pine within the state of Georgia. Tree Planters' Rotes Ec. 51: U-l4. Haller, J. R. I962. Variation in needle number in Pinus ponderosa . Abs. in Amer. Jour. Bot. ^9(6) part 2: 675-676. Harlow, W. M. 1931. The identification of the pines of the United States, native and introduced, by needle structure. N. Y. State Col. Forestry Tech. Pub. 32, 21 pp. Harper, Roland M. 1927* Natural resources of southern Florida. Fla* State Geol. Surv. Ann. Rpt. 18(1927): 27-206. Hellmers, Henry. 1962. Temperature effect on optimum tree growth. In "Tree Growth," edited by Theodore T. Koilowski. Ronald Press Co., New York, pp. 275-237.

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125 Henry, B. W. 1959* Diseases end insects in the southwide pine seed source study plantations during the first five years. Proc. Fifth South. Conf . on Forest Tree Impr., pp. 12-17* Hilmon, J. B., C. E. Lewis, and J. E. Bethune. 1962. Highlights of recent results of range research in Southern Florida. Proc. Soc. Amer. Foresters, Atlanta, Ga», pp. 73-76. Howell, John F. i960. Habitat-related variability in the cave-dwelling minnow, Hybopsis harperi . Ph. D. Thesis, Univ. of Fla., 85 pp. Huxley, J. S. 1938. Clines: an auxiliary taxonomic principle. Nature 142(3587): 219-220. Jones, L. I96I. Effect of light on germination of forest tree seed. Proc. Internatl. Seed Testing Assoc. 26(3): 437-452. Ketcham, D. E., and J. E. Bethune. 1963» F i re resistance of South Florida slash pine. Jour. Forestry 61(7): 529-530. Kramer, Paul J. 1957* Some effects of various combinations of day and night temperatures and photoperiod on the height growth of loblolly pine seedlings. Forest Sci. 3(l): ^5-55» Kriebel, Howard B. 1956. Some analytical techniques for tree race studies. Proc. Soc. Amer. Foresters I956: 79-82. Langdon, 0. Gordon. 1958a. Early trends in a slash pine seed source study in South Florida. Southeast. Forest Expt. Sta. Res. Note No. 123, 2 pp. 1958b. Cone and seed size of South Florida slash pine and their effects on seedling size and survival. Jour. Forestry 56(2): 122-127. • 1963» Range of South Florida slash pine. Jour. Forestry 5315): 384-385. Langlet, 0. I936. Studier fiver tallens fysiologiska variabilitet och dess samband med klimatet. (Studies of physiological variation in pine and its relation to climatt..) Medd. f. Statens Skogsf firsfiksanstalt . 29: 219-470. 1938. Proveniensftirsfik med olika trttdslag. (Provenance research with different tree species.) Skogsvardsffir. Tidskr. 36: 55-278. • 1959* A cline or not a cline— a question of Scots pine. Silvae Genetica 8: 13-22.

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126 Langlet, 0. 1963* Patterns end terms of lntraspecific ecological variability. Nature 200(4904): 347-348. Larson, Philip R. 1957* Effect of environment on the percentage of summerwood and specific gravity of slash pine. Yale Univ. School of Forestry Bui. No. 63, 90 pp. Little, Elbert L., Jr., and Keith W. Dorman. 1932a. Geographic differences in cone-opening in sand pine. Jour. Forestry 50(3): 204-205. , and . 1952b. Slash pine ( Pinus elliottii ), its nomenclature and varieties. Jour. Forestry 50(12): 9IB-923. . • m and . 1954. Slash pine ( Pinus elliottii ) including South Florida slash pine. Southeast. Forest Expt. Sta. Paper No. 36, 82 pp. MacNeil, F. S. 1950. Pleistocene shorelines in Florida and Georgia. U.S. Geol. Surv. Prof. Paper No. 221-f, pp. 95-107. McCulley, R. D. 1950. Management of natural slash pine stands in the flatwoods of south Georgia and north Florida. U.S. Dept. Agr. Circ. No. 845, 57 pp. Mergen, Francois. 1954. Variation in 2-year-old slash pine seedlings. Southeast. Forest Expt. Sta. Res. Note No. 62, 2 pp. • 1958. Genetic variation in needle characteristics of slash pine and in some of its hybrids. Silvae Genetica 7(1): 1-9. , and P. E. Hoekstra. 1954. Germination differences in slash pine from various sources. South. Lbrmn. 189(2364): pp. 62, 64, 66» Namkoong, Gene. I963. Comparative analyses of introgression in two pine species. Ph. D. Thesis, N. C. State Col., 76 pp. Nikles, D. G. I962. Tree breeding in Queensland 1957 to 1962. Queensland Dept. of Forestry, Brisbane (Paper for 8th British Commonwealth Forestry Conf ., East Africa, 1962), 27 pp. Pauley, Scott S., and Thomas 0. Perry. 1954. Ecotypic variation of the photoperiodic response in Populus . Jour. Arnold Arboretum 35s 167-188. Perry, Thomas 0., and Chi Wu Wang. 1955« Seed orchards for the South. Proc. Third South. Conf. on Forest Tree Impr., pp. 71-74. , and . 1957* Cooperative forest genetics research program. Univ. of Fit., School of Forestry Res. Rpt. No. 4, 27 pp.

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127 Perry, Thomas 0., and Chi Vu Vang. 1958. Variation in the specific gravity of slash pinewood and its genetic and silvi cultural implications. TAPPI kl(k): 178-180. Rao, C. Radhakrishna. 1952. Advanced statistical methods in Diametric research. John Wiley & Sons., New York, 390 pp. Schell, 6. I960. Kelmschnelligheit als Erbeigenschaft. (The heritability of gerainative energy.) StLvae Genetiea 9(2): U8-53. Schoenike, R. B., and B. A. Brown. 19^3* Variation in bark thickness of jack pine seed sources. Minn. Forestry Notes No. 130, 2 pp. Shaw, George R. 191^. The genus Pinus . Arnold Arboretum Pub. 5, 96 pp. Sherry, S. P. 19^7The potentialities of genetic research in South African forestry. Brit. Empire Forestry Conf . Proc. 19^7, Upp. Small, John Kunkel. 1933* Manual of the southeastern flora. Author, New York, 155 1 * PP« Snaydon, R. V., and A. D. Bradshaw. I961. Differential response to calcium within the species Festuca ovina L. The New Phytologlst 60(3): 219-23^. Snedecor, George V. 1956. Statistical methods. 5th Ed., Iowa State Univ. Press, Ames, 53k pp. SquiUace, A. E., and R. T. Bingham. 1958. Localized ecotypic variation in western white pine. Forest Sci. Ml): 20-3k. , and J. F. Kraus. 1959* Early results of a seed source study of slash pine in Georgia and Florida. Proc. Fifth South. Conf. on Forest Tree Impr., pp. 21-3 1 *. , and Roy Silen. 1962. Racial variation in ponderosa pine. Forest Sci. Monog. 2, 27 pp» Stearns, F., and J. Olson. 1958. Interactions of photoperiod and temperature affecting seed germination in Tsuga canadensis . Amer. Jour. Bot. ^5(1): 53-58. Stebbins, G. Ledyard, Jr. 1950. Variation and evolution in plants. Columbia Univ. Press, New York, 6U3 PP» Switzer, G. L. 1959* The influence of geographic seed source on the performance of slash pine on the Northeast Mississippi Experimental Forest. Miss. Agr. Expt. Sta. Inform. Sheet 652, 2 pp. Thames, John L. 1963* Needle variation in loblolly pine from four geographic seed sources. Ecol. Mt(l): 168-169.

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128 Thorbjornsen, Eyvind. I96I. Variation patterns in natural stands of loblolly pine. Proc. Sixth South. Conf . Forest Tree Impr., pp. 25-44. Thornthwaite, C. Warren. 1931* The climates of North America according to a nev classification. Geog. Rev. 21: 633-655. Tourney, James W., and Clarence F. Korstian. 1942. Seeding and planting in the practice of forestry. John Wiley & Sons, Nev York, 520 pp. Turesson, G. 1936. Rassenokologie und Pflanzengeographie. Bot. Notiser: 420-437. Vaartaoa, Olli. 1954. Photoperiodic ecotypes of trees. Canad. Jour. Bot. 32: 392-399. Wakeley, Philip C. 1954. Planting the southern pines. Agr. Monog. No. 18, Forest Serv., U.S. Dept. Agr., 233 PP« . 1955* Set-backs and advances in the southwide pine seed source study. Proc. Third South. Conf. Forest Tree Iagpr., pp. 10-13. • 1959. Five-year results of the southvide pine seed source study. Proc. Fifth South. Conf. Forest Tree impr., pp. 5-11. . I96I. Results of the southwide pine seed source study through I96O-6I. Proc. Sixth South. Conf. Forest Tree Impr., pp. 10-24. Ward, Daniel B. I963. Contributions to the flora of Florida— 2, Pinus ( Pinaceae ) .Castanea 23: 1-10. Weather Bureau. 1956. Climatic summary of the United States— supplement for 1931 through 1952. Alabama, Florida, Georgia, Louisiana, Mississippi, and South Carolina. Climatography of the United States Ho. 11-1 (1956), 11-6 (i960), 11-7 (1956), 11-14 (1956), 11-18 (1958), 11-33 (1956). Weather Bureau. 1959* Climates of the States: Alabama, Florida, Georgia, Louisiana, Mississippi, and South Carolina. Climatography of the United States Ko. 60-1, 60-3, 60-9, 60-lS, 60-22, 6O-3S. Weidman, R. H. 1939* Evidences of racial influence in a 25-year test of ponderosa pine. Jour. Agr. Res. 59: 855-887. Wells, Osborn 0. 1962. Geographic variation in ponderosa pine (Pinus ponderosa Dougl. ex Lavs.). Ph. D. Thesis, Mich. State Univ., 112 pp. West, Erdman, and Lillian E. Arnold. 1956. The native trees of Florida. Univ. of Fla. Press, Gainesville, 218 pp. Revised edition.

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129 Wheeler, P. R., and H. L. Mitchell. 1959* Specific gravity variation in Mississippi pines* Proc. Fifth South. Conf . Forest Tree Ing>r., pp. 87-96, , and . 1962. Specific gravity variation in Mississippi pines. U.S. Forest Prod. Lab. Bpt. No. 2250, k pp. White, John B., and H. 0. Beals. 1963. Variation in number of resin canals per needle in pond pine. Bot. Gas. 12k(h) : 251-253* Wright, Jonathan W. I9M. Ecotyplc differentiation in red ash. Jour. Forestry 1*2(8) : 591-597* , and Henry I. Baldwin. 1957* The 1938 International Union Scotch pine provenance test in Rev Haxqpshire. Silvae Genetics 6(1/2): 2-14. , and W. Ira Bull. 1962. Geographic variation in European black pine— two-year results. Forest Sci. o(l): 32-V2. , and . 1963* Geographic variation in Scotch pine. SHvae Genetica 12(1) : 1-25* * 1 and Gero Mitschelen. 19^3* Geographic variation in red pine, 3-year results. Quart. Bui. Mich. Agr. Sacpt. Sta. ^5(4): 622-630. Wright, Sewall. 19^3. Isolation by distance. Genetics 28: U^-138.

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APPENDIX

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KEY TO APPENDIX TABLE 1 Column no . Item 1 Mother tree identification. The first digit indicates group number; the second and third, stand number; and the fourth, mother tree number. 2 Sum of the lengths of seven cones—inches. Decimal between second and third digits. 3 Sum of the diameters of seven cones — inches. Decimal betveen second and third digits. 4 Average number of seeds per cone. 5 Number of seeds veighed. 6 Total weight of seeds indicated in column 5-milligrams. Column 6 divided by column 5 gives average seed weight. 7 Number of ternate fascicles in a sample of kO fascicles. 8 Sum of the lengths of 15 fascicles — millimeters. 9 Sum of the lengths of 15 fascicle sheaths — millimeters. 10 Sum of the numbers of rows of stomata on the flat surface (or surfaces) of five needles. 11 Sum of the flat surface widths of five needles — micrometer units. (100 micrometer units = 1.68 mm.) Col; 10 x 1 = number of rows of stomata per mm. of Col. 11 .0168 needle width. 12 Sum of the numbers of stomata counted in 10 stomatal rows, each 1.68 mm. long. These values, divided by 16.8, give numbers of stomata per mm. Also, Col. 10 x Col. 12 x _1 = number of stomata per Col. 11 10(.l68 2 )~ sq. mm. 13 Sum of the numbers of resin ducts counted in each of five needles. 1^ Sum of the numbers of hypoderm layers counted at four points in each of five needles. These values, divided by 20, give average numbers of layers of hypoderm per needle. 131

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132 Appendix Table 1. — Parent tree data 2.345 6 78 9 10 11 12 13 14 Lull

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Appendix Table 1 continued 133

PAGE 142

Appendix Table 1 continued 134 1

PAGE 143

135 1 1345 1351

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Appendix Table 1 continued 136 2294

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137 Appendix Table 1 continued

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KEY TO APPENDIX TABLE 2 Column no . Item 1 Seedling identification. The first digit indicates group number; the second and third, stand number; the fourth, mother tree number; and the fifth, seedling number. 2 Total height of seedling — centimeters. 3 Stem diameter of seedling — millimeters. k Data not pertinent to the study. 5 Number of ternate fascicles in a sample of 10 fascicles. 6 Sum of the lengths of three fascicles — millimeters. 7 Sum of the lengths of three fascicle sheaths — millimeters. 8 Sum of the numbers of rows of stomata on the flat surface (or surfaces) of two needles. 9 Sum of the flat surface widths of two needles-micrometer units. (100 micrometer units = 1.68 mm.) Col. 8 x 1 _ number of rows of stomata per mm. Col. 9 .0168 of needle width. 10 Sum of the numbers of stomata counted in four stomatal rows, each 1.68 mm. long. These values, divided by 6.72 give numbers of stomata per mm. Also, Col. 8 x Col. 10 x 1 = number of stomata Col. 9 .0^(1.68^) per sq. mm. 11 Sum of the numbers of resin ducts counted in each of two needles. 12 Sum of the numbers of hypoderm layers counted at four points in each of two needles. These values, divided by 8 , give average numbers of layers of hypoderm per needle . 138

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139 Appendix Table 2.— Progeny data of Nursery Test 1

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140 TO 2 52" 10253 10254 10255 1C311 10312 1C313 10314 L"0"3T5" 10321 10322 1C323 T0T24" 1C325 10331 1C332 1C333 10334 1C335 10341 10342 Appendix Table 2 continued _2_ v3F ii-lii_lQE12 ~rr 13 13 13 09 12 "22 iT6\;4tj60ltJ^C3 72 10 3 9~7j P3 13 1 :>9 6"2 OT 17 0505240C9C0 223 09 361 15 1? 149 61 04 34 C7C772C3150635 10 425 26 L5 166 61 06 37 08138305401079 LO 435 30 17 170 59 06 "22 O8C92h033C0656 09 454 19 15 162 67 04 24 070630016:3406 04 426 18 15 140 56 04 "24 U9C954023505ol 10 4 00 DJ 17 16 7 51 04 TT 29 C7085GO35C0695 10 423 26 18 164 64 C5 12 "25 07123603880643 07 540 27 16 170 56 "06 12 23_ 06C67102000502 10 426 30 15 170 56 06 16 25 06C450018C0352 05 390 20 15 158 60 04 16 27 07077202330434 10 389 30 16 166 64 04 16 TO" C7t80402oC.vJt.42 08 3
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Appendix Table 2 continued 141 1

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Appendix Table 2 continued 1U2 J. 8 10 11 12 1C654 10655

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Appendix Table 2 continued 1*3 10 11 12 1C911 10912

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Appendix Table 2 continued Ikk 11115 11121 11122 11123 _2_ 37 27 L9 2C G9 l L6500575u912 C7C3770173O333 06C456C1120254 07C566023005G7 10 10 10 09 521 371 408 423 J_ 29 21 19 24 _8 15 150 16 161 11 142 14 145 10 5 6 62 62 5 9 11 04 5 05 04 12 10 12 09" 10 11124 11125 1 1 1 3 r 11132 11133 11134 11212 11213 11214 11215 11221 11222 24 G7G7 r <5G228o552 09 488 30 10120003720712 10 462 07067C0320U658 ~06 342 07C550020703 35 1G 408 0810820470u985 09 472 G5CC540315 n 600 10 399 31 23 26 24 20 26 19 25 22 19 12 154 16 160 14 15 6" 18 174 13 140 14 155 5 3 04 5 9 06 58" 05 5 7 06 58 05 58 04 10 09 09 09 14 11 11135 11141

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11322 11323 11324" 11325 11331 11332 Appendix Table 2 continued 8 41 21 26 31 21 ~ZT 26 1 8 27 22 24 26 T T6T 4 o5o~l 5 30304 1315771260 178C "oacgarc27oobC2 091368041 10719 09067704320792 07075501920443 C7C568o2G4u394 07125C1.254' 596 0606660T520373 U8C709029C^502 07C783O230O413 G5C512C118<'208 C71C9CC28 00 6G0 08124006O0I132 C7C8621 245G527 10 4 20 08506 06 413 10 4 64 C9 444 09 448 iu 20 19 21 26 15 19 11 15 18 16 9 T52 TT 169 5 9 129 "82 160 65 166 54 158 62 1*5 10 11 12 04 04 04 04 06 14 14 14 16 14 14 TY73T 11334 11335 11341 11342 11343 11344 11345" 11351 11435 11441 11442 11443 11444 11445 36 23 TO 07 08 10 10 09 10 09 09 474 510 406 390 4 36 362 451 494 490 27 2 6 15 19 21 25 21 25 25 14 15 14 14 18 13 17 lb 20 163 56 1 5 7 5 8 15 1 60 1 5 7 6 1 148 52 14 2 6 2 179 70 161 156 70 5 8 04 05 04 06 08 06 05 05 05 37 C71C2C048J0684 23 ,,06 0490015 10 345 24 06053101400229 10 090575C227C415 20 07069102250268 34 C8C992055CL802 06 491 0932 7 ~09 37 I 10 528 10 452 10 413 26 21 15 18 15 26 21 14 10 11 16 15 17 -j 150 159 129 165 169 56 55 63 57 06 _°j4_ 04 07 61 57 04 06 T6 14 ri 13 14 12 16 16 16 11352 11353

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Appendix Table continued 1^6

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147

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Appendix Table 2 continued 148 1

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Appendix Table 2 continued 149 1

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Anpendix Table 2 continued 150 1

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151 12554 12 5 5 5 12611 12 612 2 9 Lo'O 7400242 03 8 31 o^ioo003151173 32 0/077002950663 31 0307 002650 5 2 5 Appendix Table 2 continued 10 10 10 01 407 496 551 551 2/ 34 29 17 8_ 16 21 17 11 JL.. 15. J 186 150 120 10 5 5 54 58 61 11 05 06 06 04 12 15 16 14 13 12 613 12614 12615 1262 i_ 12622 12623 3 7 u /08650500082-O 06 504 22 16 13 7 69 05 12 33 07092003 1505 70 OJ 541 2b 16 14b 67 06 09 25 08089503650655 10 522 30 14 150 59 05 16 34 07 149504300944 10_487 27_ 14. 155 65 04_ 13 2b 07103003720662 06 463 17 13 151 61 04 12 31 0/070202780661 09 514 25 13 157 62 04 15 13123 13124 13125 13131 13132 13 133 12624 12625

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152 Appendix Table 2 continued

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Appendix Table 2 continued 153 1

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Appendix Table 2 continued 154 1

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155 1

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Appendix Table 2 continued 156 1

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157 Appendix Table 2 continued 1

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158 Appendix Table 2 continued 1

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Appendix Table 2 continued 159 1

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160 Appendix Table 2 continued

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161 Appendix Table 2 continued 1

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162 Appendix Table 2 continued

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Appendix Table 2 continued 163 34742 34 74 3 34744 34745 10 100592023 J0532 L2 09082503390732 10 09082002880734 11 090909038 10720 _5_ 04 05 01 02 508 554 507 577 _7 2b lo lo 2a _8_ 12 13 12 11 130 123 118 122 JLO 11 60 04 52 04 58 04 56 05 _12 11 11 12 11 34751 34752 34753 34 7 54 34753 34821 09 12048803000620 08 532 17 12 12v 08 09042501500310 _07 564 21 12 130 16 W092002950639 07 638 33 12 146 05 ^06039800900265 03_411 17 10 121 08028001020258 05 504 lo 12 142 10066002410765 04 633 22 lb 162 0/ 09 60 04 09 58 04 10 61 04 13 6 5 4 13 5 3 04 09 5 3 04 11 34822 3482_3_ 34324 34825 34841 34842 08 07049001920528 09 08067702020719 06 03003500210044 6 09063 9020205 7 4 09 07052601810562 09 09063101500492 04 571 _Q5_70 7 05 700 0_7_565 05 561 09 594 25 15 33 la 21 20 12 14 15 11 15 1 I 122 130. 152 127 141 149 04 05 59 55 60 05 50 05 57 54 04 0b 11 11 11 10 10 10 34843 34844 3484 5 34851 34852 34853 10 08059001470615 08 07044 L01200368 09 10077002200644 11 10066803250548 09 09033601910378 11 0b0672019u06 2 9 09 497 04 551 08 516 09 4 37 0-3 4 62 05 652 20 20 Id 16 21 2o 14 135 12 141 12 142 14 121 id 132 14 137 5b 5 9 61 73 51 57 04 04 05 04 04 14 09 11 10 11 10 34854 _34_85_5_ 34911 _3_49 1 2_ 34913 34914 11 08040002240418 1 1 10078302500724 551 4 67 06 il0630018>0463 09 12064503150583 09035502500528 JO/5002750708 12 12 07 09 06 534 8 434 09 5 39 06 52 3 20 2J, 21 lo 2'+ 16 13 132 14 121 13 133 13 146 12 133 10 130 60 56 04 04 57 49 04 04 09 12 11 1 L 59 60 04 04 13 12 34915 34921 34922 349 23 34924 34925 09 09053502100333 0=> 0804730 1760507 07 08050501530590 03 0603400092035o 08 03 561 549 32 17 12 12 133 136 56 b2 04 04 10 11 09 03054901820367 07 06036000900247 10 525 _09__495 07 615 05 444 16 lo 24 23 10 121 11 123 16 170 13 150 57 5 ) 58 67 04 04 14 12 04 04 09 09 34931 34932 3493 3 34934 34935 34941 13 12060203320595 11 100595023^0750 13 10072304000340 13 _11064503J00898 11 10 09085202680743 10058902600544 09 10 07 09 05 09 636 544 697 60b 656 574 34 31 23 19 35 19 14 150 18 170 14 143 15 155 13 161 10 136 60 60 60 6 64 04 05 04 _04 08 04 10 12 08 13 10 12 34942 34943 34944 _3494 5 349 51 34952 09 07042001200315 10 10052102500916 11 13060002550749 8 090 5350192 6 6 5 13 08060303220794 05 0/032101000299 07 564 00_53 6 03 498 09 5 42 566 531 08 07 la 20 1 / lo 27 17 10 1 3 0b 13 12 10 133 130_ 126 125 52 5 9 6d 5 5 121 142 55 5b 04 04_ 04 04 05 06 10 JLL 15 12 10 11 34953 34954 34955 35011 05 060400007b0226 07 07041501310389 13 03053202330531 18 100633 035 4094 3 04 04

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164

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KEY TO APPENDIX TABLE 3 Column no. Item 1 Row plot identification. The first digit indicates group number; the second and third, stand number; the fourth, mother tree number; and the fifth, replicate number. 2,3*^ Data not pertinent to the study. 5 Number of seeds sown. 6 Number of seeds germinated as of 3/29 • 7 Number of seeds germinated as of U/lO. Col. 7 x 100 germinability in per cent. Also, Col. 5 Col. 6 x 100 = speed of germination in per cent. Col. 7 8 Sum of the numbers of cotyledons on a sample of seedlings (see Col. 9) . 9 Number of seedlings on which cotyledon counts were made. Col. 8 = number of cotyledons per seedling. Col. 9 10, 11 Data not pertinent to the study. 165

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166 Appendix Table 3. — Progeny data of Nursery Test 2 10 11 10111

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Appendix Table 3 continued 167 1

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168 Appendix Table 3 continued 1

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Appendix Table 3 continued 169 1

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Appendix Table 3 continued 170 1

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Appendix Table 3 continued 171 1

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Appendix Table 3 continued 172 1

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Appendix Table 3 continued 173

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174 1

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Appendix Table 3 continued 175

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176 1

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Appendix Table 3 continued 177 1

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Appendix Table 3 continued 178 1

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Appendix Table 3 continued 179 1

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Appendix Table 3 continued 180 1

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Appendix Table 3 continued 181 1

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BIOGRAPHICAL SKETCH Anthony E. Sqtdllace was born Septeaaber 16, 1915# at Kinney, Minnesota. In June, 1933* he was graduated from Martin Hughes High School* After 3 years of temporary employment with the Civilian Conservation Corps and U.S. Forest Service, he resumed schooling at the Virginia Junior College, and University of Minnesota, earning a Bachelor of Science degree in Forestry from the latter in lyhQ. From 19^0 to 19^2 he was employed by the Consolidated Water Power and Paper Company at Grand Marais, Minnesota. From I9U3 to 19^5 he served with the U.S. Army in the United States and Europe. In 19*16 he began permanent employment with the U.S. Forest Service, serving as Research Forester at stations in Montana, Washington, and Florida, and, aside from interruptions for further schooling, has continued in this position to the present time. He obtained a Master of Science degree in Forestry and Botany at the University of Montana in 1955, and enrolled in the Graduate School of the University of Florida in I960. Anthony E. SquiUace is married to the former Dorothy Alice Babbinl and is the father of three children. He is a member of the Society of American Foresters, XI Sigma Pi, Phi Sigma, and Gamma Sigma Delta.

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This dissertation vaa prepared under the direction of the chairman of the candidate's supervisory committee and has bees approved by all members of that committee. It vaa submitted to the Dean of the College of Agriculture and to the Graduate Council, and vas approved as partial fulfill went of the requirements for the degree of Doctor of Philosophy. April 18, 196k M. A. Brooker Dean, College of Agriculture Supervisory Committees L. S. Grinter Dean, Graduate School , , . ,^, ^_ — V. 6. Ut A. D. Conger

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Ill