HISTORICAL BIOGEOGRAPHY OF PRESENT-DAY
Wilfred T. Neill
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Published 9 December 1957
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HISTORICAL BIOGEOGRAPHY OF PRESENT-DAY FLORIDA
WILFRED T. NEILL
SYNOPSIS: Numerous Floridian plants and animals have geographic ranges
which reflect both environmental conditions of today and geologic and climatic
events of the past, especially those of the Pleistocene. Seven biogeographic areas
are recognized for the state, and the associated faunas and floras are described.
.The present paper is concerned with patterns of animal and plant
distribution in Florida, and the ways in which these patterns may have
come about. The terminology employed should be clear in most
cases, but certain usages should be defined. Thus, by "race" I mean
"subspecies," although the terms are not synonymous in some fields.
The word "Pleistocene" should also be explained. Geologists no longer
recognize a Recent epoch; to them the Pleistocene has not ended
(Flint, 1947; Hibbard, 1949; Ray, 1949). However, from a zoological
point of view, it is desirable to distinguish between the very last part
of post-Pliocene time, characterized by a modern fauna, and the pre-
ceding part when elephants, giant bison, etc. were present in Florida.
The term "recent" (with a lowercase "r") is used in an informal or
local sense to designate these last millenia. Pleistocene and recent
are thus distinguished faunistically. To some, "endemic" means "hav-
ing arisen in the area it now occupies;" to others it means "limited to
a given area," and I have used the word in this latter sense. For con-
venience, the trinomial has been omitted from many scientific names;
and for readability, literature references in some cases have been
placed at the end of the paragraph to which they relate, rather than
scattered throughout the sentences. Finally, my comments on the
ranges of flying organisms, unless otherwise stated, refer only to
breeding ranges and not to areas covered by migrations or other
Every organism is confined to an area where its special environ-
mental requirements are met. However, in order to explain present
distribution patterns, one must consider not only the environmental
conditions that prevail today, but also the different ones that obtained
1 Wilfred T. Neill, author of numerous papers in many fields, including herpe-
tology, anthropology, archeology, and paleontology, is in charge of the Research
Division of the Ross Allen Reptile Institute at Silver Springs, Florida. The present
paper is an outgrowth of a Phi Sigma lecture delivered at the University of
Florida, 15 March 1956. Manuscript received 11 February 1957.-Eu.
BULLETIN FLORIDA STATE MUSEUM
not long ago, geologically speaking. As past conditions cannot be
studied directly, historical biogeography must draw inferences from
paleontological, climatological, and geological data as well as from
the known facts of present-day animal and plant distribution.
The historical approach to biogeography is not the only one; there
is also the ecological (Hesse, et al., 1937). The latter is outside the
scope of the present paper. For information concerning the present
natural features and ecology of Florida, see Alexander (1953), Carr
(1940), Collins and Howard (1928), Cooke (1939), Davis (1940, 1943),
Dice (1943), Fenneman (1938), Ferguson, et al., (1947), Harshberger
(1914), Henderson (1939), Hubbell, et al., (1956), Kurz, (1928, 1942),
Laessle (1942), Mulvania (1931), Odum (1953), Sellards (1910, 1912),
Wright and Wright (1932), and especially Harper (1914, 1921, 1927).
Climatic data are provided by Mitchell and Ensign (1928), Thorn-
thwaite (1931), U.S. Department of Agriculture (1941), Visher (1954),
and Ward and Brooks (1936).
At one time the peculiarities of the Florida biota were explained
simply as a direct result of the geographic position of the state. It
was customary to say that Florida pointed southward, carrying a tem-
perate biota toward the tropics; that the aforesaid peculiarities were
adaptations to a subtropical environment. A good bit of raciation in
southern Florida may actually reflect adjustment to subtropical habi-
tats, abetted in some cases by insulation. Thus, on the Keys, in the
Everglades, or elsewhere in southern Florida, there are local races of
many widespread species, including the short-tailed shrew (Blarina
brevicauda), the eastern mole (Scalopus aquaticus), the raccoon (Pro-
cyon lotor), the mink (Mustela vison), the gray squirrel (Sciurus car-
olinensis), the fox squirrel (S. niger), the rice rat (Oryzomys palustris),
the cotton rat (Sigmodon hispidus), the white-tailed deer (Odocoileus
virginianus), the red-shouldered hawk (Buteo lineatus), the red-bellied
woodpecker (Centurus carolinus), the white-eyed vireo (Vireo griseus),
the redwing (Agelaius phoeniceus), the corn snake (Elaphe guttata),
the rat snake (E. obsoleta), and many others (Neill, 1949; Sherman,
1937, 1952; Sprunt, 1954).
Some widespread stocks occur throughout much of Florida with-
out evident modification therein. Examples are the eastern hognose
snake (Heterodon platyrhinos), the coachwhip (MasticopFlis flagellum),
the six-lined racerunner (Cnemidophorus sexlineatus), the southeastern
five-lined skink (Eumeces inexpectatus), the common musk turtle
(Sternotherus odoratus), the eastern spadefoot (Scaphiopus holbrooki),
and numerous birds (Carr and Goin, 1955; Sprunt, 1954). Indeed,
NEILL: BIOGEOGRAPHY OF FLORIDA
space will not permit discussion of origins in areas remote from Florida
beyond the comment that some animal and plant groups may have
originated in the southern Appalachians (Adams, 1902; Hobbs, 1942;
Ortmann, 1902), and that, among ectotherms, many lines of descent
trace back toward the southwestern United States and northern Mexico
(Blanchard, 1921; Hobbs, 1942; Neill, 1949; Ruthven, 1908). Suffice
it to say that many widespread stocks have reached Florida; that some
of them have undergone raciation in the southern part of the state,
perhaps as a result of the subtropical conditions that prevail there.
However, adjustment to the demands of a subtropical environment
will not explain the generic distinctness of many central Florida en-
demics, or the presence of essentially northern or upland plants and
animals in isolated colonies along the panhandle of the state. One
must search for other factors that may have brought about or modified
patterns of distribution in Florida.
GLACIAL LOWERING OF TEMPERATURE
The Pleistocene was characterized by fluctuations of climate. At
least four times in that epoch great ice sheets formed in both hemi-
spheres. There is still argument as to whether the glaciers were the
cause of, or the result of, a lowering of temperature (Landsberg, 1949).
At any rate, glacial times in North America saw a fairly widespread
chilling. "Over the world the temperature averaged 7 to 14 degrees
colder [than at present]" (Field, 1955, p. 86). The presence of ice
sheets up to 10,000 feet thick, covering as much as a third of the
northern hemisphere and a considerable portion of the southern,
drastically affected wind currents and the distribution of rainfall; and
because vast quantities of water were impounded in the ice, sea level
fell as the glaciers advanced, rose as they retreated. To further com-
plicate matters, the advances and retreats were not smooth but pro*
gressed by fits and starts, with occasional reversals of direction. There
were, for example, at least twelve advances and retreats of the Wis-
consin ice sheet; and environmental conditions must have fluctuated
accordingly (Sears, 1948). Pollen profiles from bogs often reveal
marked changes in floral composition, reflecting climatic variations.
In one bog as many as eight climatic changes have been detected,
correlated with fluctuations of the Wisconsin ice (idem).
Nevertheless, Florida was comparatively remote from the actual
glaciers, and one may ask whether a lowering of temperature was evi-
dent so far south even during peaks of glaciation. Palynological analy-
sis of a boring from Marion County, Florida, revealed pollen of fir
BULLETIN FLORIDA STATE MUSEUM
and spruce in a Pleistocene stratum (Davis, 1946). Pollen of cold-
weather plants, such as fir, Canadian spruce, larch, and arborvitae,
have been recovered from a number of Pleistocene localities between
western Florida and eastern Texas, in some cases with cold-water mol-
lusks (Potzger and Tharp, 1943, 1947, 1954). It is now well established
that boreal genera and species extended their ranges far south during
glacial times (Potzger and Tharp, 1954). Some of the range exten-
sions appear to reflect the last or Wisconsin glaciation. Thus, a pollen
profile from Lake Singletary, in the coastal plain of North Carolina,
included a stratum with fir, spruce, and pine, but almost no broad-
leaved trees; and this stratum, indicative of cold weather, could be
correlated with the Mankato advance of the Wisconsin ice (Frey,
1951). Some Lake Singletary radiocarbon dates are provided by
Subarctic Foraminifera were present in a submarine core collected
from the Gulf of Mexico. In this core there was a gradual progression
from the modern, subtropical Foraminifera at the top to the subarctic
ones farther down, implying that the waters of the Gulf were relatively
cold during the last glaciation (Trask, et al., 1947). A core from the
Caribbean yielded cold-weather Foraminifera, some regarded as arc-
tic; they were present at several levels (Phleger, 1948). Cold-water
diatoms have been found at several localities in Florida in deposits
underlain by the Pamlico formation (Gunter and Ponton, 1933; Hanna,
1933). As the Pamlico is no older than the Sangamon or last inter-
glacial period (Cooke, 1939, 1945), an overlying stratum with cold-
water diatoms should be of Wisconsin age.
Near St. Petersburg, Florida, remains of the eastern porcupine
(Erethizon dorsatum) occur in a late Pleistocene stratum, along with
those of a lemming-mouse (Synaptomys australis) (Sherman, 1952;
Simpson, 1929). By historic times the porcupine had retreated a
thousand miles northward; and the extant Synaptomys, at least, are
boreal (Anthony, 1928). The muskrat (Ondatra zibethica) occurred,
in northern Florida during the Pleistocene (Lawrence, 1942) Ilrl ...h i.
today it is lacking from the state as well as from southern G,-,.r. a c d.d
southern Alabama. A muskox reached Florida in the Pleistc. .-.!!e And
one of the mammoth elephants known from this state is tho I.ht tI he
a cold-weather species (Potzger and Tharp, 1954).2 A II-! r1..n.c
elk (Cervus species) has been reported from the Melboufne formation.
but its specific identity is uncertain (Gazin, 1950). Within .Ir. .r.c
'The muskox is not mentioned by other authors dealing with the Fl-.r-d
1957 NEILL: BIOGEOGRAPHY OF FLORIDA 179
times the American elk (C. canadensis) ranged southward into the
uplands of South Carolina (Logan, 1859). A fox (Vulpes palmaria),
also from the Melbourne formation, was "very close to, if not identical
with the [modern] red fox" (Sellards, 1916, p. 152). The latter (V.
fulva) now ranges southward only into northern Georgia and Alabama
LOWER TEMPERATURE OR HIGHER RAINFALL?
As noted, pollen of fir and spruce have been recovered from a
Pleistocene stratum in central Florida. However, this does not nec-
essarily imply a period of extremely cold weather in the peninsula.
The studies of Oosting and Hess (1956) are useful in this connection.
These authors point out that there is a relic stand of Canadian hemlock
in the lower Piedmont of North Carolina, well south of the general
range of this plant. Evidently the hemlock once ranged southward
into the lower Piedmont, then retreated northward again, leaving a
relic colony. The microclimate of this hemlock stand is unusually
moist, not unusually cold. It seems possible that increased rainfall,
rather than colder weather, once permitted the hemlock to extend
its range southward. This may have been the case with other species.
Dillon (1956) believed that the supposed palynological evidence
of former chilling actually reflects higher rainfall more than lower
temperature. He stated that, because of the Wisconsin ice sheet,
"a mean annual low-pressure system would have developed over the
glaciated region. As a result, the mean annual cyclonic path . .
would have been displaced to the south . (p. 168). This circum-
stance would have increased precipitation in both the southeastern
and southwestern United States. According to Dillon, Florida would
have had 40 to 60 inches of rain annually, and more than 60 inches in
some parts of the state. The present annual rainfall is scarcely less
However, Dillon did not contend that Florida was completely un-
affected by glacial chilling; rather the reverse. He noted that, while
Florida has an extensive tropical flora, it has extremely few endemic
plants of tropical affinities. This circumstance "seems to indicate the
complete elimination of suitable climatic factors for . persistence
[of a tropical flora in the state] during Wisconsin times" (p. 173). In
other words, Dillon granted some glacial chilling in Florida, sufficient
to eliminate a tropical flora.
Ericson, et al., (1956) derived climatic data from deep-sea sediments.
They remarked: "The shells of planktonic Foraminifera in deep-sea
BULLETIN FLORIDA STATE MUSEUM
sediment cores provide the most trustworthy evidence on climatic vari-
ations of the Pleistocene because they vary in accordance with the
temperature changes in the surface of the ocean and because the .
stages are represented in chronological sequence" (p. 385). They
found that the modern warm period began 13 to 15 thousand years
ago, and had been preceded by a definitely colder one; and they com-
mented: "This world-wide change of surface-water temperature at
the end of the glacial period argues against any theory of continental
glaciation which calls on increased precipitation only without lower-
ing of the world mean annual temperature" (p. 387).
Ewing and Donn (1956) found evidence, based on Foraminifera,
that the mean annual temperature declined 1PC. per 11,000 years,
from 90,000 to 11,000 years before the present, and thereafter in-
creased 1C. per 1,000 years, at least until a few thousand years ago.
The studies of Phleger (1948) and of Trask, et al., (1947), previously
mentioned, imply that there was glacial chilling even farther south
It seems likely that, during Wisconsin times, Florida was somewhat
cooler and rainier than at present. It was too cool to support a tropi-
cal flora, cool and wet enough to support some organisms which today
characterize the Transition or even more northerly life zones. How-
ever, its biota was for the most part of Lower Austral species (Dillon,
Of course, earlier glaciations than the Wisconsin may have affected
Florida more severely; on this point there is little information. Dur-
ing Illinoian times, the five-lined skink (Eumeces fasciatus) and the
worm snake (Carphophis arnoena) ranged into central Florida (Auffen-
berg, 1956). Today the skink barely enters northern Florida (Neill
and Allen, 1950), and the worm snake, in my opinion, does not occur
naturally south of the piedmont in Georgia. The aforesaid studies on
Foraminifera indicate several cold periods, some more severe than
"NORTHERN DISJUNCTS" AND OTHER SPECIES IN THE FLORIDA PANHANDLE
Certain aspects of animal and plant distribution in the Florida pan-
handle may reflect either former cooling or the heavy rainfall of Wis-
consin times or both. In the panhandle one encounters populations of
essentially northern or upland species confined to isolated spots far
south of their present continuous ranges. This situation could have
resulted only if the species involved once pushed southward and then
retreated northward again, leaving isolated colonies in favorable areas.
1957 NEILL: BIOGEOGRAPHY OF FLORIDA 181
However, one must remember that a good share of the "northern ele-
ment" in the panhandle probably is not isolated there. The Gulf
coastal plain of western Georgia and Alabama is relatively high, in
some ways more reminiscent of the piedmont than of the Atlantic
coastal plain. Traveling southward from the piedmont of western
Georgia, one encounters no marked change of scenery until well below
Tallahassee; the vista throughout is one of rolling, red clay hills cov-
ered with loblolly and shortleaf pines. (Kurz, 1928, has discussed the
"northern" aspect of the Tallahassee Red Hills.) Such northern plants
as whitecedar, beech, trilliums, pallid and shagbark hickories, swamp
leatherwood, big-leaved and Frasers magnolias, bloodroot, mandrake,
columbine, hepatica, bellworts, Solomons-seal, baneberry, pepperroot,
rue-anemone, false rue-anemone, swamp buttercup, giant equisetum,
etc. reach Florida mostly or only in the panhandle (Cowles, 1904;
Harper, 1914; Kurz, 1933, 1939; Murrill, 1946; Small, 1933), but it is
improbable that all of them are isolated there. Judging from Duncan's
(1950) spot maps, a number of trees occupy fairly continuous ranges
from northern Georgia to, and into, northwestern Florida. Small
(1938) believed that glacial chilling had brought some northern ferns
into the Florida panhandle, but he also realized (p. 7) that some species
merely ranged from the piedmont through the relatively high country
of western Georgia and eastern Alabama, and so into northwestern
Florida. Thorne (1949, 1954) noted the occurrence of various inland
and upland plants on the Gulf coastal plain of Georgia; and some of
these reach the Florida panhandle. Certain of the "northern" animal
species almost surely are not isolated, but merely find the southern
extremities of their respective ranges in northwestern Florida. Many
essentially upland animals are unable to invade the Atlantic coastal
plain of eastern Georgia for more than a few miles, yet break out of
the piedmont into the higher Gulf coastal plain and range nearly or
quite into the Florida panhandle. Examples are the Alleghenian
spotted skunk (Spilogale putorius), the swamp rabbit (Sylvilagus aquat-
icus), the five-lined skink (Eumeces fasciatus), the copperhead (Agkis-
trodon contortrix), the mole snake (Lampropeltis calligaster), the mid-
land brown snake (Storeria dekayi wrightorum), Fowler's toad (Bufo
woodhousei fowleri), the northern dusky salamander (Desmognathus
f. fuscus), the spotted salamander (Ambystoma maculatum), and per-
haps the silverjaw minnow (Ericymba buccata) (Allen and Neill,
1955b; Carr and Goin, 1955; Grobman, 1950; Hamilton, 1943; Neill,
1950, 1954b; Taylor, 1935; Trapido, 1944). The list could be extended
BULLETIN FLORIDA STATE MUSEUM
Some other animals are widespread throughout much of the South-
east, avoiding only the lower parts of the coastal plain. Consequently
they are present in the Florida panhandle but not elsewhere in the
state. In this category are the three-lined salamander (Eurycea longi-
cauda guttolineata), the southern red salamander (Pseudotriton ruber
vioscai), the Gulf Coast mud salamander (P. montanus flavissimus),
and the southern cricket frog (Acris g. gryllus) (Bishop, 1943; Carr
and Goin, 1955).
Many organisms range widely in the Gulf drainage (some of these
well up the Mississippi drainage as well) and therefore inhabit the
Florida panhandle. Among them are the central dusky salamander
(Desmognathus fuscus brimleyorum), the western bird-voiced tree-
frog (Hyla p. phaeocrypta), the Gulf Coast box turtle (Terrapene caro-
lina major), the gray rat snake (Elaphe obsoleta spiloides), the green
water snake (Natrix c. cyclopion), four shiners (Notropis roseipinnis,
N. signipinnis, N. venustus, and N. longirostris), the longfin madtom
(Schilbeodes funebris), the southern brook lamprey (Ichthyomyzon
gagei), the northern spotted bass (Micropterus punctulatus), the long-
ear sunfish (Lepomis m. megalotis), the southern rock bass (Amblo-
plites rupestris ariommus), the Gulf Coast waterdog (Necturus beyeri),
the Mobilian turtle (Pseudemys floridana mobilensis), and two cray-
fishes (Procambarus versutus and Cambarus diogenes) (Bishop, 1943;
Carr and Coin, 1955; Dendy and Scott, 1953; Grohman, 1950; Hobbs,
1942; Neill, 1948, 1949). Here again, the list could be extended
Some species or races are characteristic of the Mississippi Valley
or of the western Gulf Coast, and range no farther east than the
western end of the Florida panhandle. Examples are the Gulf Coast
redwing (Agelaius phoeniceus littoralis), the brown-headed ... I,,:h
(Sitta p. pusilla), the western mud snake (Farancia abacura ruci IirJr i.
the western cottonmouth (Agkistrodon piscivorus leucost ...... I el
stripe-necked musk turtle (Sternotherus minor peltifer), the ma buna
map turtle (Graptemys pulchra), and a crayfish (Procamb. r., ... .r-
manni) (Cagle, 1954; Hobbs, 1942; Sprunt, 1954; Tinkle a'..l \\rl,b
1955). In many species-e.g., the aforesaid mud snake, cottolia.wuth,
and musk turtle-a race of the western Gulf coastal plain intergrades
with a more easterly race near the western end of the Florida pan-
handle. Twenty-four species of fishes, occurring in the Mississippi
drainage, find the eastern limits of their respective ranges in the pan-
handle. Of these, fourteen range no farther east than the Choctaw-
hatchee, if that far; the remainder reach the Apalachicola (Bailey,
et al., 1954). Among fishes entering only the western end of the pan-
1957 NEILL: BIOGEOGRAPHY OF FLORIDA 183
handle are the quillback (Carpiodes cyprinus), the alligator gar (Lepis-
osteus spatula), the blacktail redhorse (Moxostoma poecilurum), the
streaked topminnow (Fundulus olivaceus), and the star-gazing darter
(Hadropterus uranidea) (Carr and Goin, 1955).
Thus many northwestern Florida organisms afford no evidence of
a southward migration in former times. There are, however, a few
upland animals which appear to have truly isolated populations in
northern Florida. These include the red-spotted newt (Diemicty-
lus v. viridescens), the mountain chorus frog (Pseudacris brachyphona)
(possibly a distinct race [Neill, 1954b]), the eastern ribbon snake
(Thamnophis s. sauritus), and the midland water snake (Natrix sipedon
pleuralis). The last occurs in the Choctawhatchee ravines; the others
are found at both ends of the panhandle (Neill, 1954b). The presence
of the four-toed salamander (Hemidactylium scutatum) near the Flor-
ida-Georgia border may also be significant (Grobman, 1954). There
are seemingly disjunct populations of two bats (Myotis keeni and M.
grisescens) in Jackson County, Florida, but the circumstance may re-
flect only the distribution of limestone caves (Rice, 1955a, 1955b).
The aquatic insect larvae of the panhandle ravines are of characteristic-
ally upland species in many cases, some of them occurring nowhere
else south of the piedmont (Berner, 1950; Byers, 1930; Carr, 1940;
Rogers, 1933). The commonest crayfish of the Apalachicola ravines,
Cambarus latimanus, is generally considered Appalachian (Carr, 1940;
Hobbs, 1942). A northern camel cricket, Ceuthophilus gracilipes, is
not found south of the fall line, except in the Apalachicola region of
Florida where a distinct race exists (Hubbell, 1936).
Among the amphibians and reptiles of northwestern Florida, there
are at least five instances in which two races of the same species occur
in the same area, ecologically separated-newts, Diemictylus v. virides-
cens and D. v. louisianensis; dusky salamanders, Desmognathus f.
fuscus and D. f. auriculatus; cricket frogs, Acris g. gryllus and A. g.
crepitans; ribbon snakes, Thamnophis s. sauritus and T. s. sackeni;
water snakes, Natrix sipedon fasciata and N. s. pleuralis. In each case
except that of Desmognathus, the essentially northern race occupies a
limited area surrounded by the more typically southern one, and in
each case except that of Acris, the more northerly race is restricted to
relatively cold situations (Grobman, 1950; Neill, 1954b). This cir-
cumstance, coupled with the spotty distribution of some "northern"
elements in the panhandle and with the paleontological evidence of
former chilling, suggests that the Gulf coastal plain has undergone a
faunal and floral turnover which is not quite complete. In other words,
during Wisconsin times, what we now call the "northern element" may
BULLETIN FLORIDA STATE MUSEUM
well have been the predominant one in the panhandle, along with
other species no longer present in the state. In this connection one
notes the presence of the muskrat in the Apalachicola region about
2500 years ago (Neill and Bullen, 1955). Lacking from the state today,
it reached Alachua County in the northern part of the peninsula in the
Pleistocene (Lawrence, 1942).
Florida east of the panhandle, and the lower Atlantic coastal plain
of southeastern Georgia, were also exposed to glacial chilling and
once supported some supposed cold-weather organisms, as shown by
Pleistocene remains. The cold-weather biota has nearly vanished from
these areas, which topographically and climatologically are unlike the
piedmont. Nevertheless, there seem to be a few relic colonies of es-
sentially upland species isolated at favorable localities well to the east
of the panhandle. A rhododendron (Rhododendron Chapmanii), long
thought to be an Apalachicola endemic, has been subsequently found
at one spot in northeastern Florida (Totten, 1945). The star-nosed
mole (Condylura cristata) has been taken in Okefinokee Swamp near
the Georgia-Florida border, far south of its continuous range (Hamil-
ton, 1943). Several amphibians and reptiles, essentially of the pied-
mont or upper coastal plain, have been reported in northeastern or
central Florida at points which I find almost incredibly far south: for
example, the marbled salamander (Ambystoma opacum) has been re-
ported in the Tampa Bay region (Carr and Coin, 1955); the painted
turtle (Chrysemys picta) near Jacksonville (Deckert, 1918); the spotted
turtle (Clemmys guttata) in Lafayette County (Grobman, 1954) and
Marion County (Carr, 1940); and the brown king snake (Lampropeltis
calligaster rhombomaculata) from "the St. Johns River" and from
Lake County (idem).
ENDEMISM IN THE FLORIDA PANHANDLE
The Florida panhandle is noted not only for its "northern" element
but also for many endemic species or races, some of which range a
short distance into Georgia or Alabama. Among these endemics are
the Florida yew (Taxus floridana), the torreya (Torreya taxifolia), the
croomia (Croomia pauciflora), a sedge (Carex Baltzelli), a spiderlily
(Hymenocallis Kimballiae), a plume-locust (Amorpha bushii), a bass-
wood (Tilia porracea), a violet (Viola rugosa), a meadowbeauty (Rhexia
parviflora), a gum (Nyssa ursina), a water-parsley (Sium Floridanum),
a milkweed (Asclepias viridula), a goldenrod (Solidago flavovirens),
three asters (Aster plumosus, A. brachypholis, and A. spinulosus), a
waterlily (Nymphaea ulvacea), a waxweed (Parsonsia lythroides), a
NEILL: BIOGEOGRAPHY OF FLORIDA
basil (Clinopodium dentatum), three camelcrickets (Ceuthophilus um-
brosus, C. armatipes, and C. rogersi), a flightless grouse-locust (Tettigi-
dea empedonepia), a distinctive katydid (Hubbellia marginifera), a
remarkable opilionid (Siro americanus), the Okaloosa darter (Etheo-
stoma okal6osae), a bass (Micropterus species), a sawback turtle (Grap-
temys barbouri), a kingsnake (Lampropeltis getulus goini), a black-
snake (Coluber constrictor helvigularis), and a water rat (Neofiber alleni
apalachicolae) (Auffenberg, 1955a; Bailey and Hubbs, 1949; Cagle,
1952; Carr, 1940; Carr and Goin, 1955; Harper, 1949; Hobbs, 1942;
Hubbell, 1936, 1940; Neill and Allen, 1949; Schwartz, 1953; Small,
Although some panhandle endemics are confined to the Apalachi-
cola region, it should be noted that many are not found there. Thus,
two Potamogeton are restricted to the mouth of the Blackwater River;
a Grossularia grows around Lake Miccosukee; a basswood (Tilia por-
racea) inhabits Okaloosa County; a mint (Stachys lythroides) grows
in sandy places near Tallahassee; a waterlily is confined to the western
end of the panhandle; a false-indigo (Baptisia hirsuta) is known from
dry sand areas in Okaloosa and Walton Counties, and another (B.
simplicifolia) occurs in Wakulla and Gadsden Counties; a camel-
cricket (Ceuthophilus armatipes) is known only from DeFuniak Springs
and perhaps Pensacola; and a distinctive whirligig beetle (Gyretes
iricolor) has been found only in the Choctawhatchee drainage (Carr
and Coin, 1955; Harper, 1949; Hubbell, 1936; Small, 1933; Young,
1947). A crayfish of the genus Procambarus is endemic to Escambia
County; two are confined to the Escambia River, one to the vicinity
of Panama City, and one to Leon and Wakulla Counties (Hobbs,
1942). A crayfish of the genus Cambarus has been taken only from a
well in Jackson County, and another is confined to the western end
of the panhandle (idem).
The northwestern Florida endemics seem clustered around the
Apalachicola region and the western end of the panhandle. The
"northern element" is similarly distributed. It is therefore reasonable
to guess that the endemism and the northern aspect of the panhandle
biota are but two facets of the same problem. In other words, I sus-
pect that many of these endemics once were typical, widely ranging, 4
Gulf Coast forms at a time when the climate was cooler and wetter
than at present. A sawback turtle (Graptemys barbouri), thought to
be an Apalachicola endemic, was subsequently found in the Escambia
River about 125 miles to the west (Cagle, 1952). A camel cricket (Ceu-
thophilus rogersi) has been reported only from the Apalachicola ravines
and from Mobile, Alabama (Hubbell, 1936). A crayfish (Procambarus
BULLETIN FLORIDA STATE MUSEUM
versutus), ranging from Mississippi through the western end of the
Florida panhandle, occurs also in the Apalachicola region; and the
apparently disjunct distribution cannot be laid to inadequate collecting
(Hobbs, 1942). Three species of freshwater mollusks are common in
the Escambia and the Apalachicola, yet have never been found in the
Choctawhatchee in spite of intensive collecting (Clench and Turner,
1956). As mentioned previously, a rhododendron, once thought to be
an Apalachicola endemic, was found to occupy a tiny area of the
Atlantic coastal plain in Clay County, Florida (Totten, 1945). Some
of the true Apalachicola endemics, such as the Florida yew and the
Torreya, occur at two, three, or more separate localities (Kurz, 1927,
1939). In other words, some of the endemics, like some of the "north-
ern" species, are discontinuously distributed, perhaps for the same
EAST-WEST DISTRIBUTION IN T1E FLORIDA PANHANDLE
Peculiarities of cast-west distribution in the panhandle cannot be
laid to temperature correlated factors or to general similarities between
that region and the country farther north. Rather, these peculiarities
seem to reflect mostly the interglacial rises of sea level. Being rela-
tively high except along its southern edge, the panhandle was never
entirely submerged, but its rivers were embayed by the rising sea.
During interglacial periods there was an embayment occupying the
Escambia-Blackwater-Yellow River basin, another occupying the Choc-
tawhatchee-Alaqua basin, and a third involving the Apalachicola and
its tributaries. At their maxima these embayments extended well into
what are now Georgia and Alabama (Cooke, 1945). Many an organ-
ism now finds the eastern or the western limit of its range at one of
these former embayments. The larger streams of the western pan-
handle mark the eastern limit of range for numerous fishes character-
istic of the Mississippi Valley and Gulf coastal plain, and the western
limit for various species occurring on the Atlantic coastal plain (Bailey,
et al., 1954). At each rise of sea level the Apalachicola drainage was
embayed farther inland than any other; and today the Apalachicola
proper appears to be an exceptionally important barrier to east-west
distribution in many groups. I suggest that the barrier is not the
present river but the broad saltwater channel that occupied its position
during long periods of the Pleistocene.
Clench and Turner (1956) studied the freshwater mollusks of the
Gulf drainage from the Escambia River to the Suwannee. They noted
a lack of endemic species in streams such as the Ochlockonee and the
NEILL: BIOGEOGRAPHY OF FLORIDA
Suwannee, which arise in the lowlands, but numerous endemic species
in the Apalachicola, Choctawhatchee, and Escambia Rivers, which
arise in higher country. They concluded that the valleys of the low-
land streams must have been inundated by Pleistocene rises of sea
level, and that endemic species could have developed only in those
streams whose headwaters, at least, remained above the encroaching
salt water. Thus the distribution of freshwater mollusks in the Florida
panhandle helps to confirm the geological evidence of extensive em-
baying during the Pleistocene.
It was noted that both the endemic and "northern" elements of
northwestern Florida seem to cluster around the Apalachicola region
and the western panhandle. This circumstance in part may reflect
the presence of suitable habitats in these areas-ravine streams, for
example-and their absence from intervening territory. However, it
is significant that both the endemic and "northern" elements are com-
posed largely of species that live in or near freshwater brooks, creeks,
and rivers, or in situations that develop in the floodplains of such
streams. Along the lowland rivers, populations of these species
mostly would have been wiped out by Pleistocene rises of sea level and
concomitant encroachment of salt water; but along the Apalachicola
and the larger streams of the western panhandle, the same organisms
could have avoided extermination by retreat toward the headwaters.
With a fall of sea level, the various species could again have moved
downstream; but they could not have come to reoccupy the streams
from which they had been exterminated unless they were able to cross
the land barriers between drainages.
ENDEMISM AND OTHER DISTRIBUTIONAL PHENOMENA IN
The rises of sea level that embayed the panhandle well-nigh inun-
dated what is now central Florida. Some land remained in the pen-
insula, however. The highest Pleistocene marine terrace is the Brandy-
wine, about 270 feet above present sea level. Even if there has been
no erosion or land subsidence, the Brandywine sea would have left
a fair-sized island in Polk County and several smaller islands just
north of there. This situation is now recognized by geologists (Cooke,
1945). There is also reason to suppose that erosion has reduced the
level of the central Florida hills. These hills are mostly of fine sand,
easily worn down by wind or rain; and climatologists say that glacial
periods were extremely windy and rainy. Cooke (1945, p. 247) stated,
"All parts of Florida . were subject to erosion during every glacial
BULLETIN FLORIDA STATE MUSEUM
stage. . The central Florida hills may be lower today than ever
before. Furthermore, there is evidence of recent land subsidence
affecting the western part of the peninsula, as I shall point out later.
Granting that Pleistocene submergence in central Florida was not
complete, one may trace the Cenozoic history of the state as outlined
by Campbell (1940), Cooke (1939, 1945), Schuchert (1935), and White
(1942). The area was completely submerged during the Eocene. In
the Oligocene an island, the so-called Ocala Island, was exposed in
what is now the upper part of the peninsula. It remained separate
from the mainland but may have become connected with Cuba. In
the late Oligocene it was nearly or completely submerged. During the
Miocene an island appeared again, and toward the end of this epoch
contact was established between this island and the mainland. Florida
remained a peninsula all during the Pliocene. Up to this time the sub-
mergences and emergences had been the result of crustal movements.
The first glaciation of the Pleistocene withdrew water from the sea,
and the size of the Florida peninsula was considerably augmented.
The first interglacial reduced the peninsula to a group of islands, the
sea rising 270 feet above its present level. Thereafter, there were
cycles of interglacial rise and glacial fall of sea level; but each cycle
was less marked than the preceding one. The relatively high rises of
Pleistocene sea level came during the early part of that epoch; subse-
quent rises left ample land in what is now the peninsula.
The central Florida region, corresponding roughly to the Pleisto-
cene archipelagos, embraces a strip down the "backbone" of the pen-
insula, from Marion County in the north through Highlands County
in the south. It is an area of rolling sand hills, whose dunelike struc-
ture can be seen at many localities. These hills are covered with
xerophilous rosemary scrub or with high pine, although mesophytic
and hydrophytic situations develop in low spots. In most areas there
is an abrupt transition from the central Florida highlands to the border-
ing lowlands. The rolling area reaches a maximum elevation of 325
feet in Polk County. Elevation decreases northward of this point; and,
although the highlands continue as a weakly defined ridge northward
into Georgia, the impressively high country comes to an end around
Alachua County. This is another way of saying that the salt water
channel between the Pleistocene islands and the mainland ran approxi-
mately through Alachua County. Biogeographers have 'called this
channel the Suwannee Straits, because the Suwannee River and its
tributaries now occupy what was formerly the channel bed.
A short distance north and also west of the central Florida region
there are smaller, isolated areas of comparatively high elevation.
NEILL: BIOGEOGRAPHY OF FLORIDA
These, too, may mark the position of former islands, of middle Pleisto-
Rosemary scrub is the first timber stage following cessation of activ-
ity in coastal dunes (Carr, 1940; Laessle, 1942). It occurs on stabilized
dunes just back of the present coast; and, significantly, on the central
Florida hills which are thought to mark the position of Pleistocene
islands. High pine succeeds rosemary scrub (Carr, 1940) or, like scrub,
may initiate succession (Laessle, 1942). Many central Florida en-
demics, both plant and animal, are mostly confined to scrub, high
pine, or the two associations together. For example, the scrub lizard
(Sceloporus undulatus woodi), the sand skink (Neoseps reynoldsi), and
the Florida jay (Aphelocoma c. caerulescens) are seldom found outside
rosemary scrub; the short-tailed snake (Stilosoma extenuatum) is char-
acteristic of high pine; the brown red-tailed skink (Eumeces egregious
onocrepis) occurs in both and rarely invades other associations. Harper
(1949) recognized 189 flowering plants endemic to central Florida, and
I would judge from Small's (1933) comments that about 60 percent
of them characterize one or both of the sandhill associations.
Rosemary scrub is replaced by other associations during the course
of ecological succession (Laessle, 1942). This being the case, some
areas of scrub, particularly small ones, may have vanished completely.
Scrub-limited animals would have vanished from the areas at the same
time. There is paleontological confirmation of this view. Pleistocene
deposits in western Alachua County have yielded remains of the island
glass lizard (Ophisaurus compresses) and the scrub jay (Auffenberg,
1955b; Pierce Brodkorb, personal communication). The lizard in-
habits scrub and certain littoral or supratidal situations, while the bird
is confined to scrub. The lizard, the jay, and the plant association are
all lacking from the area today, the nearest locality for all three being
in northeastern Marion County.
Many typical central Florida organisms fall into one of two cate-
gories. Some are closely, usually subspecifically, related to a main-
land form; others are very distinctive species, often comprising mono-
typic genera or subgenera, not closely related to anything now living
in North America. Presumably the members of the second group may
have persisted there as relic species after most of their allies in other
regions had died out.
Among the central Florida organisms with near relatives elsewhere
are the Florida spotted skunk (Spilogale ambarvalis), the Florida pine
mouse (Microtus pinetorum parvulus), the Florida flying squirrel
(Glaucomys volans querceti), the Florida cotton mouse (Peromyscus
gossypinus palmarius), the central Florida rice rat (Oryzomys palustris
BULLETIN FLORIDA STATE MUSEUM
natator), the Florida cotton rat (Sigmodon hispidus littoralis), the
Florida marsh rabbit (Sylvilagus palustris paludicola), the Florida
crow (Corvus brachyrhynchos pascuus), the Florida wren (Thryothorus
ludovicianus miamensis), the Florida bobwhite (Colinus virginianus
floridanus), the Florida turkey (Meleagris gallopavo osceola), the Flor-
ida pine warbler (Dendroica pinus florida), the Florida blue bird
(Sialia sialis grata), the Florida redwing (Agelaius phoeniceus mearnsi),
the Florida crown snake (Tantilla coronata wagneri), the Florida king
snake (Lampropeltis getulus floridana), the Florida banded water snake
(Natrix sipedon pictiventris), the scrub lizard (Sceloporus undulatus
woodi), the Florida snapping turtle (Chelydra serpentina osceola), the
peninsula turtle (Pseudemys floridana peninsularis), the Florida mud
turtle (Kinosternon subrubrum steindachneri), the Florida chorus frog
(Pseudacris nigrita verrucosa), the peninsula newt (Diemictylus viri-
descens piaropicola), the peninsula dusky salamander (Desmognathus
fuscus carri), the Florida black bass (Micropterus salmoides floridanus),
and the central Florida black widow spider (Latrodectus mactans var.
bishop) (Carr, 1940; Carr and Goin, 1955; Hamilton, 1948; Kaston,
1938; Sherman, 1937, 1952; Sprunt, 1954). In most of these species,
the peninsular population is a race, intergrading with a mainland one
at the level of the old Suwannee Straits. If it is granted that some
forms, originating on the Pleistocene islands, were able to spread a
short distance northward after closure of the Straits, then other species
could be added to the list.
Among the very distinctive peninsular endemics, perhaps relic
species, are the striped mud turtle (Kinosternon bauri), the sand skink
(Neoseps reynoldsi), the worm lizard (Rhineura floridana), the short-,
tailed snake (Stilosoma extenuatum), and the gopher mouse (Peromys-
cus floridanus). The round-tailed water rat (Neofiber alleni), the black
swamp snake (Seminatrix pygaea), Allen's swamp snake (Liodytes
alleni), and the mud siren (Pseudobranchus striatus) probably should
be added, although they now range a short distance out of Florida.
The genus Pseudobranchus is known from the recent of Florida and
nearby areas, as well as from the Pleistocene and Pliocene of Florida;
the lineage appears to be an ancient one within the state (Coin and
Among peninsular plants, there are a number of distinctive ferns,
delicate species mostly growing in limestone situations. Although
their affinities are tropical, they are confined to the upper part of the
peninsula; and the groups to which they belong are represented in the
tropical West Indies but not in southern Florida. This circumstance
led St. John (1936) to contend that Ocala Island, once continuous with
1957 NEILL: BIOGEOGRAPHY OF FLORIDA 191
Cuba, was never completely submerged but had persisted since the
Oligocene. Carr (1940) attempted to bring fern distribution into line
with the evidence of complete submergence in the late Oligocene. He
suggested that during a warm interglacial, fern spores blew or drifted
to the Pleistocene islands of central Florida, persisting in the sheltered
environment of caves and lime sinks.
There are several monotypic genera of flowering plants in central
Florida: a pea, Chapmannia; composites, Garberia, Hartwrightia, Am-
mopursus, and Litrisa; a pennyroyal, Pycnothymus; a milkweed,
Oxypteryx; a St. Johnswort, Sanidophyllum; and a dayflower, Trades-
cantella (Harper, 1949; Small, 1933).
One may surmise that the short-tailed snake is a relic species, be-
cause it has no known close relatives, living or fossil. Likewise, one
may postulate that the worm lizard is a remnant of an ancient and
formerly widespread group, because other species of its genus are
known from the Oligoccne of Colorado, Nebraska, South Dakota, and
Wyoming (Taylor, 1951). The only known congener of the round-
tailed water rat is from the middle Pleistocene of Kansas and Texas
(Meade, 1952). However, in the absence of paleontological data it
would be temeritous to say which central Florida species developed
their present characters on the Pleistocene islands and which simply
persisted there from an earlier period. Suffice it to mention a few
more organisms chiefly or strictly peninsular. The Florida short-
tailed shrew (Cryptotis floridana) and the Florida black bear (Ursus
floridanus) range northward into southeastern Georgia. The Ever-
glades short-tailed shrew (Blarina brevicauda peninsula) is confined
to the southern part of the peninsula; its range may be disjunct from
that of the Carolina short-tailed shrew (B. b. carolinensis), which has
been reported no farther south than Alachua County. The Florida
prairie warbler (Dendroica discolor collins) is strictly peninsular, and
its breeding range may be disjunct from that of the more northerly
race (D. d. discolor); the latter breeds no farther south than central
Georgia. Perhaps the limpkin (Aramus guarauna pictus) reached the
Pleistocene islands from the south, evolving into a distinct race in-
habiting the southeastern United States as well as Cuba. The Florida
red-bellied turtle (Pseudemys nelsoni) is found throughout the penin-
sula, north to Alachua and Levy Counties. The island glass lizard
(Ophisaurus compressus) is found on islands and coasts of South Caro-
lina, Georgia, and Florida, and in the central Florida scrub areas
which are thought to represent former islands. The striped newt
(Diemictylus perstriatus) of central Florida ranges northward into
southern Georgia (Carr, 1940; Carr and Goin, 1955; McConkey, 1954;
BULLETIN FLORIDA STATE MUSEUM
Sherman, 1937, 1952; Sprunt, 1954). A characteristic insect of the
peninsular sandhills is the roach, Arenivaga floridensis, the females of
which are flightless, and whose nearest relatives are found in Texas.
A scarabaeid beetle (Onthophagus polyphemi) is known only from
tortoise burrows; it has been reported from Florida and South Caro-
lina. Several Florida invertebrates are obligate inquilines in tortoise
burrows; and some, like the histerid beetle, Chelyoxenus xerobatis,
are relic species with no near relatives. Although they are not now
confined to peninsular Florida, it is likely that they survived in that
region and have subsequently spread. A comparable group of in-
vertebrates inhabits burrows of the pocket gopher (Geomys pinetis);
and some Florida aspects of this symbiosis may have developed on
the Pleistocene islands. A blind camel cricket (Tt.bIl...... ,t.l,.7,i,.
floridanus), belonging to a monotypic genus, is strictly peninsular and
confined to pocket-gopher burrows. A camel cricket (Ceuthophilus
latibuli) ranges from central Florida to extreme southern Georgia, often
inhabiting tortoise burrows; and another species (C. peninsularis) in-
habits peninsular Florida from Pinellas County to Dade County. Four
grasshoppers (Schistocerca ceratiola, Melanoplus forficatus, M. indici-
fer, and M. tequestae) are confined to rosemary scrub, as is a wolf-
spider (Lycosa ceratiola). The distribution of certain flightless sand-
beetles (Mycotrupes species) has been explained in terms of sea level
fluctuations which isolated populations in central Florida and else-
where. A race of a waterstrider (Metrobates anomalus) is known only
from Hillsborough and Polk Counties (Hubbell, 1932, 1936, 1940, 1954;
Hubbell and Goff, 1940; Hussey, 1948; Hussey and Herring, 1949;
Young and Goff, 1939).
Clench and Turner (1956) commented on the distribution of fresh-
water mollusks in Florida. They were impressed by the number of
species that did not range east or south of the Suwannee, and by the
distinctiveness of the central Florida molluscan fauna. They felt that
there was "good evidence among the freshwater mollusks for the
existence of an island in what is now central Florida during the period
of fluctuation of the epicontinental Pliocene and Pleistocene seas"
(p. 104); and that the failure of many species to range below the
Suwannee "is undoubtedly explained by the fact that at the time of
[the island, the Suwannee valley] was inundated" (p. 105). They
further suggested that the island must have been large enough to have
had a freshwater drainage system with some lakes and perhaps some
fairly large creeks. Dall (1890-1903, see 1903), another student of
mollusks, had previously remarked that there must have been fresh-
NEILL: BIOGEOGRAPHY OF FLORIDA
water lakes on a central Florida island or archipelago, and that these
lakes must have been in existence from quite an early period.
A pallid, cavernicolous crayfish (Procambarus 1. lucifugus), known
from caves in Citrus and Hernando Counties, is associated with a
white isopod (Asellus hobbsi) and a blind, white amphipod (Crangonyx
hobbsi). One of the most remarkable central Florida organisms is the
crayfish, Troglocambarus maclanei; blind, attenuated, and almost
transparent, it lives on the ceilings of submerged caverns in Citrus and
southern Alachua Counties. Its extreme specialization indicates a
lengthy separation from other crayfish stocks; and its existence may
imply the persistence of subterranean fresh water, and therefore of
land, for quite a long while in this part of Florida. A distinctive cray-
fish (Procambarus alleni) inhabits cypress ponds of the peninsula;
another (P. geodytes) is known from mineral springs in Marion, Put-
nam, and Seminole Counties; and yet another, the zoologically dis-
junct P. acherontis, has been taken only in Seminole County, from
sinks, springs, and subterranean waters (Hobbs, 1942, 1944).
A freshwater sponge (Myenia subtilis) is known from but one lake,
in Osceola County (Eshleman, 1950).
The freshwater ichthyofauna of the peninsula is depauperate, unless
one counts the marine species that venture inland. The cyprinids,
suckers, and darters, represented abundantly elsewhere in the south-
east, have very few members below the Suwannee Straits. With the
closing of the Straits, the earliest and most successful invaders from
the continent probably were cyprinodonts, characteristic of brackish
coastal waters. Today the peninsula has a number of endemic cyprin-
odonts, including the red-finned killifish (Lucania goodei), the ocellated
killifish (Leptolucania ommata), the Caledonian (Fundulus seminolis)
and the Lake Eustis sheepshead killifish (Cyprinodon hubbsi), as well
as about 14 more widely ranging members of this family. A peninsular
centrarchid, the Florida black bass (Micropterus salmoides floridanus),
intergrades with the mainland race about the region of the Suwannee
Straits. A few other fishes are endemic to, or chiefly characteristic of,
the peninsula (Bailey and Hubbs, 1949; Carr, 1937a; Carr and Coin,
The sand pine (Pinus clause), the rosemary (Ceratiola ericoides),
a marshgrass (Spartina Bakeri), a saw-palmetto (Serenoa repens), and
three oaks (Quercus Chapmanii, Q. myrtifolia, and Q. virginiana var.
geminata) typify central Florida but range into other states. A false
pimpernel (Ilysanthes grandiflora) is strictly peninsular, ranging from
Marion County to Glades County. A cactus (Opuntia ammophila),
a lupine (Lupinus cumulicola), a plum (Prunus geniculata), a bluet
BULLETIN FLORIDA STATE MUSEUM
(Houstonia pulvinata), a composite (Palafoxia Feayi), a willow (Salix
amphibia), a persimmon (Diospyros Mosieri), three buckthorns (Bu-
melia species), a rockrose (Crocanthemum Nashii), several pinweeds
(Lechea species), a yellow waterlily (Castalia flava), a morning-glory
(Bonamia grandiflora), two mints (Scutellaria arenicola and Trichos-
tema suffrutescens), a grape (Vitis Simpsonii), a swectbay (Tamala
humilis), the wild olive (Osmanthus americana), the dwarf cabbage-
palm (Sabal Etonia), a wild buckwheat (Eriogonum floridanum), a
holly (Ilex cumulicola), two papaws (Pityothamnus species) and some
xerophilous selaginellas are nearly or entirely confined to the central
Florida region. Many of these are strikingly modified for life in dry
situations, and grow in scrub or high pine. A bellflower (Rotantha
robinsiae) has been reported only from one hilltop near Brooksville,
IIernando County; and a clematis (Clematis micrantha) is also known
only from Brooksville. Other plants, endemic to central Florida, could
be listed (Harper, 1949; Small, 1933).
Of course, some species, now considered endemic to the Florida
peninsula, may eventually be found well outside that area. However,
this circumstance does not especially weaken biogeographic arguments
based on endemism in central Florida; the ranges of many organisms
have been traced with considerable accuracy, and, for many of the
peninsular endemics, significant range extensions are not to be ex-
SOME MINOR ASPECTS OF DISTRIBUTION IN CENTRAL FLORIDA
Various minor aspects of plant and animal distribution in central
Florida seem to reflect Pleistocene insulation. Thus, some peninsular
races intergrade only sporadically with their more northerly counter-
parts, there being a good deal of interpenetration in separate habitats.
This is true, for example, of the brown snakes (Storeria dekayi wright-
orum and S. d. victa), the red-bellied snakes (Storeria o. occipitomacu-
lata and S. o. obscure), the fence lizards (Sceloporus u. undulatus and
S. u. woodi),3 the softshell turtles (Amyda f. ferox and A. f. aspera),
the dusky salamanders (Desmognathus fuscus auriculatus and D. f.
carri), and perhaps the cardinals (Richmondena c. cardinalis and R. c.
floridana) (Neill, 1948, 1950, 1951a, 1951b; Sprunt, 1954; Trapido,
1944). If the peninsular races had simply developed lineally from
mainland stocks, intergradation should be smooth and probably grad-
3 Although intergradation between these two lizards has not been reported in
print, it does take place. An intergradient series of individuals was displayed by
James M. Boyles and me at the 1953 meeting of the American Society of Ichthy-
ologists and Herpetologists, Southeastern Division, held at Athens, Georgia.
NEILL: BIOGEOGRAPHY OF FLORIDA
ual. Sporadic intergradation, with interpenetration in separate habi-
tats, implies a recent recombination of stocks long isolated geograph-
ically. It is also significant that, in some cases, the range of the more
northerly cpmponent bends southward around that of its central Flor-
ida counterpart, as though, with the bridging of the Suwannee Straits,
the central Florida population remained in situ while the more north-
erly one flowed around it. In this connection note Hubbell's (1954, p.
44) distribution map for vicariating species of the sand beetle genus
Mycotrupes, and Carr's (1940, p. 75) county records for red-tailed
skinks, now called Eumeces egregius similis and E. e. onocrepis. A
similar situation exists among the kingsnakes (Lampropeltis getulus
subspecies). In the interior of Florida, the transition from the more
northerly L. g. getulus to the peninsular L. g. floridana is accomplished
from central Ala6hua County to central Marion County; but on the
west coast L. g. getulus occurs at least as far south as northern Citrus
County. If temperature-correlated factors were the only controlling
agents of racial or vicarious distribution in these cases, the peninsular
components should swing northward up the coast as do the isotherms.
This is the reverse of the actual situation. It is also interesting to note
that quite a few of the central Florida endemics, relic or otherwise,
do not occupy the entire sandhills region, but are confined to areas
which apparently correspond in position with certain of the Pleisto-
cene islands. Thus the sand skink (Neoseps reynoldsi), a scrub-limited
species, is lacking from the apparently suitable Big Scrub (described
below) of Marion County, and occurs only in the higher dune areas
farther south. The races of the short-tailed snake (Stilosoma extenu-
atum) roughly correspond in distribution with islands of the Wicomico
sea (Highton, 1956). Some recognizable insect populations are associ-
ated with presumed island areas; these include a color variant of a
stick insect (Anisomorpha buprestoides), confined to the Big Scrub
(Hetrick, 1949), as well as various grasshoppers and sand beetles
(Hubbell, 1932, 1954).
It might be argued that I have included among the central Florida
endemics more organisms than could have lived on small Pleistocene
islands. However, the conditions that obtain in the present-day Big
Scrub suggest otherwise. This area, in eastern Marion County, is
sharply distinct from the surrounding terrain, and is thought to repre-
sent one of the former islands. In the Big Scrub there are three enor-
mous springs, with flows of 68 to 83 million gallons per day; two
springs flowing 68 and 83 hundred thousand gallons per day respective-
ly; uncounted smaller springs and seepage areas; about 20 sizeable
creeks and streams in addition to the major spring runs; over 100 lakes,
BULLETIN FLORIDA STATE MUSEUM
some of large size; hundreds of smaller lakes, ponds, and swampy de-
pressions; dunelike expanses of deep sand; areas of xerophilous rose-
mary scrub and of high pine; liveoak hammock; stands of mesophytic
magnolia, blue beech, American holly, dogwood, etc.; low hammock;
cypress swamp; wide, grassy "prairie"; and dense bayheads. The Big
Scrub alone supports a large percentage of the central Florida endem-
ics, along with other more widespread species.
A sizeable group of organisms apparently occupied the Pleistocene
islands; most of the available niches must have been filled. If so,
numerous mainland species must have found it difficult to invade the
peninsula when the Suwannee Straits were bridged. One would ex-
pect to find mainland forms stopping short at the level of the Straits
today, even though their characteristic habitats may continue farther
south. This is the case. Mainland forms, stopping approximately in
Alachua County, include Bachman's shrew (Sorex 1. longirostris), the
Carolina short-tailed shrew (Blarina brevicauda carolinensis), the red
bat (Lasiurus b. borealis), the old-field mouse (Peromyscus p. poliono-
tus), the indigo bunting (Passerina cyanea), the wood thrush (Hylo-
cichla mustelina), Swainson's warbler (Limnothlypis swainsoni), the
hooded warbler (Wilsonia citrina), the orchard oriole (Icterus spurius),
the sharp-shinned hawk (Accipiter striatus velox), the marsh hawk
(Circus cyaneus hudsonius), the red-bellied water snake (Natrix ery-
throgaster), the smooth ground snake (Haldea valeriae), the canebrake
rattlesnake (Crotalus horridus), the alligator snapping turtle (Macro-
chelys temmincki), the yellow-bellied turtle (Pseudemys scripta, the
spotted sucker (Minytrema melanops), the Alabama chubsucker (Eri-
myzon tenuis), the southeastern creek chub (Semotilus atromaculatus),
the iron-colored shiner (Notropis chalybaeus), the mud perch (Acan-
tharchus pomotis), the brown darter (Etheostoma edwini), and five
crayfishes (Carr and Coin, 1955; Hobbs, 1942; Sherman, 1937; Sprunt,
Even some flying insects do not cross the Suwannee Straits. The
dragonfly genus Progomphus includes only two species in the eastern
United States. One evolved on the Pleistocene islands of central
Florida, the other on the mainland. With the bridging of the Straits,
the mainland form apparently was unable to extend its range below
Alachua County (Cross, 1955). The butterfly, Colias eurytheme, wide-
spread in North America, does not range below the Suwa'nnee Straits
(Hovanitz, 1950). Stoncflies have not been reported in Florida below
Alachua County (Berner, 1948).
The case of the aforesaid red-bellied water snake and of the yellow-
bellied turtle are particularly impressive. In southern Georgia these
1957 NEILL: BIOGEOGRAPHY OF FLORIDA 197
reptiles are hardy, abundant, and well-nigh ubiquitous in aquatic sit-
uations; yet in Alachua County they stop abruptly even though their
habitats continue southward. This county, and Marion County im-
mediately to the south, have been centers of intensive herpetological
collecting for many years, and one can feel rather sure that the south-
ernmost localities for the two species have actually been located.
A number of other mainland species cross the Straits area only
along the coasts, and swing southward around the old island area.
Some of these are not especially characteristic of coastal situations else-
where, and are not replaced by near relatives in central Florida. In-
cluded in this category are the eastern blue grosbeak (Guiraca c.
caerulea), the eastern wood peewee (Contopus virens), the rough-
winged swallow (Stelgidopteryx ruficollis serripennis) and Peterson's
shiner (Notropis petersoni) (Carr and Coin, 1955; Sprunt, 1954). The
mink (Mustela vison) appears to avoid the old island region entirely;
it is present in northern and southern Florida, including both coasts,
but has never been found in central Florida (Allen and Neill, 1952 and
therein; Hamilton, 1943; Sherman, 1937). A distribution of this
sort is consistent with the theory of central Florida insulation.
A few mainland species are able barely to penetrate the extreme
northern edge of the old island region, having been collected no
farther south than the level of central Marion County. These include
the rough ground snake (Ialdea striatula), the gray treefrog (Hyla
versicolor), the river frog (Rana lwckscheri), the flatwoods salamander
(Ambystoma cingulatum), and several freshwater sponges (Carr, 1940;
Carr and Coin, 1955; Eshleman, 1950; Sherman, 1937). The yellow-
throated vireo (Vireo flavifrons) is essentially confined in Florida to
the region north of the Straits, but has lately been found at Orlando;
the range extension may represent a recent invasion of the peninsula
(Sprunt, 1954). Presumably these species were lacking from the
central Florida islands.
DISTRIBUTION OF COASTAL AND MARINE ORGANISMS
The distribution of coastal and marine organisms may also reflect
Pleistocene insulation. A large number of marine fishes, including a
sea lamprey, stingrays, sharks, the tarpon, a weakfish, a pipefish, a
croaker, a remora, sea catfishes, and four flatfishes enter peninsular
Florida waters (Carr and Coin, 1955). Odum (1953) pointed out that
Florida fresh waters yet contain a good deal of salt in consequence of
sea level changes during the Pleistocene. He apparently felt that the
saltwater species merely travel upstream from the ocean; but Carr
BULLETIN FLORIDA STATE MUSEUM
(1937a) implied that some of the freshwater populations were virtually
isolated from the marine ones. Perhaps the reduction of the peninsula
to an archipelago made it easier for marine organisms to reach the
oligohaline waters. At any rate, a naturalist, visiting one of the clear
springs that well up from the Big Scrub of Marion County, will be
surprised to see mojarra (Eucinostomus argenteus), sole (Trinectes
maculatus fasciatus), stingrays (Dasyatis species), needlefish (Strongy-
lura marina) and mullet (Mugil species); as well as blue crabs (Callinec-
tes sapidus), a smaller crab (Rithropanopeus harrisi), and marine
As regards amphibians and reptiles, the Florida peninsula has more
"freshwater" species in salt water, and more "inland" species in supra-
tidal habitats, than any other part of the world, so far as I can learn
(Neill, MS a). The drowning of the peninsula, thrice repeated, may
have forced some species into saltwater habitats or favored the sur-
vival of species that could exist in such places. Some freshwater in-
vertebrates also invade brackish waters in Florida (Berner and Sloan,
1954; Sloan, 1956).
Certain patterns of coastal distribution in Florida are revealing.
That of the coastal marsh wren (Telmatodytes palustris) is an example.
One race of this bird is found on the Atlantic coast from South Caro-
lina to Volusia County, Florida; another inhabits the Gulf Coast from
Charlotte Harbor to Mississippi. Thus the distribution in Florida is
split into upper east coast and upper west coast components, although
the species is lacking from the shores of the southern peninsula. Dee-
vey (1950) remarked on similar cases of split distribution among
hydroids and suggested that glacial chilling once permitted these
temperature-limited invertebrates to swing around the southern tip
of Florida. Whatever happened among hydroids, I think that in-
stances of split distribution in other groups mostly reflect passage
through the Suwannee Straits at a period of high sea level. In other
words, the species involved once ranged along the former mainland
shore on the north side of the Straits; the distribution was split when
the peninsula emerged and the Straits closed. Carr and Coin (1942)
advanced a similar explanation to account for the distribution of salt-
water snakes (Natrix sipedon subspecies) in Florida. In these reptiles
there is a peninsular race (N. s. compressicauda) intergrading in
Brevard County with an upper east coast race (N. s. tapniata) and
around Pasco County with an upper west coast race (N. s. clarki). N. s.
taeniata and clarki are very similar although separated by the mark-
edly divergent compressicauda. Carr and Coin postulated that corn-
pressicauda developed on a Pleistocene island while the old mainland
1957 NEILL: BIOGEOGRAPIIY OF FLORIDA 199
shore was occupied by a common ancestor of taeniata and clarki.
With the bridging of the Straits, the former mainland population was
split, diverging slightly to produce clarki and taeniata; compressicauda
was left about the peninsular shores. The history of the seaside spar-
rows (Ammospiza maritima subspecies) may have been comparable.
Two races thereof occupy the upper east coast, and three others the
upper west coast; the group is lacking from the southern peninsular
shores except for a stretch between Cape Sable and Everglades City,
where an isolated population (at present called a distinct species, A.
mirabilis) is found. There are also three races of the clapper rail
(Rallus longirostris) in Florida: one on the upper east coast, one on
the west coast, and one on the Keys. One race of the yellow-throated
warbler (Dendroica dominica) ranges, mostly coastally, from Maryland
to mid-Florida; another occupies the Gulf lowlands from Levy County
west to the Choctawhatchee River. A single race of the mink (Mustela
vison lutensis), inhabiting salt marsh, is known from Duval and St.
Johns Counties on the east coast, and from Levy County on the west
coast. Several fishes, crabs, and mollusks are found on both coasts of
northern Florida, yet are lacking from the peninsula or its southern
part (Deevey, 1950 and therein; Sherman, 1937; Sprunt, 1954).
RECENT RISE OF SEA LEVEL
The Wisconsin ice sheet is still shrinking, and sea level has risen
within the recent period (Goggin, 1948). Certain aspects of distribu-
tion in Florida may reflect this rise. The greater siren (Siren lacertina)
occurs in the only body of permanent fresh water on Merritt Island,
off the coast of Brevard County. It does not cross land or salt water,
and so may have been trapped on the island by a recent rise of the
sea (Neill, 1954b). Many of the present offshore islands must have
been produced since the peak of the Wisconsin glaciation, by separa-
tion from the mainland as the sea encroached upon the land. The
populations isolated on these islands might have diverged from the
parent ones through selection and perhaps genetic drift. As the islands
are not far offshore, they probably have been invaded by mainland
organisms at fairly frequent intervals. According to Miller (1956, p.
276), ... moderate but not full isolation of populations favors prompt
initial and subsequent evolutionary progress as made particularly clear
by Sewall Wright." Thus one can account for the numerous bird and
mammal races confined to such islands as Anastasia, Merritt, Santa
Rosa, the Ten Thousand Islands, and certain of the Keys. The en-
vironment of southern Florida may have hastened evolution of insular
200 BULLETIN FLORIDA STATE MUSEUM Vol. 2
populations in that area. That is to say, many faunal groups (e.g.,
mammals, reptiles, and amphibians) are represented in southern Flor-
ida largely or entirely by species which originated farther north; and
these species, originally adapted to temperate conditions, may have
been subjected to unusually strong selective pressures in consequence
of invading an area of tropical plant associations and subtropical
ENDEMISM IN NORTHEASTERN FLORIDA
Northeastern Florida (east of the panhandle and north of the Su-
wannee Straits) is another area of endemism, about 26 species of
flowering plants being confined to this part of the state (Harper, 1949;
Small, 1933). Some of them belong to widespread and remarkably
polytypic genera, such as Solidago, the goldenrods; Aster, the asters;
Helianthus, the sunflowers; Opuntia, the pricklypears; Cracca, the
hoary peas; Eleocharis, the spikerushes; and Scleria, the nutrushes.
These throw little light on the problem of endemism in northeastern
Florida. However, two of the endemics, a cycad (Zamia umbrosa)
and a dwarf sunflower (Phoebanthus tenuifolia), find their close rela-
tives only to the south, in the old island area. Perhaps a central Flor-
ida stock of Zamia and of Phoebanthus once crossed to the mainland
and became isolated there with a rise of sea level. The Sunderland
sea of the second interglacial not only insulated central Florida; it also
left a group of islands in what is now northeastern Florida. The
Wicomico sea left a peninsula there, pointing toward the central
Florida islands; the Penholoway permitted a narrow connection be-
tween this peninsula and central Florida; the Talbot and Pamlico left
a broad connection (Cooke, 1939). One might expect a localization
of species or races in an area which, so often and for so long, was a
sizeable peninsula during the Pleistocene, and which could have been
colonized from both north and south.
RECENT LAND SUBSIDENCE IN WESTERN FLORIDA
Florida has been exposed not only to fluctuations of sea level but
also to comparatively recent land subsidence along its western edge.
At one time, geologists held that there had been no late Pleistocene or
recent tilting along the Atlantic seaboard. This conclusion was based
on the fact that a late Pleistocene shore line, the Pamlico, maintains the
same altitude from New Jersey to southern Florida (Rouse, 1951 and
therein). However, this situation reveals only that there has been no
tilting in a north-south direction. Subsidence of the Florida west coast
has taken place, probably in consequence of the great weight of sedi-
NEILL: BIOGEOGRAPHY OF FLORIDA
ments poured into the Gulf by the Mississippi River (Storm, 1945).
Marine shells associated with the Pamlico shore line occur up to 25
feet above present sea level on the Florida east coast, but only up to
10 feet on the west coast (Rouse, 1951 and therein); in Louisiana, near
the focus of subsidence, shells thought to be of Pamlico age have been
taken from a boring at a depth of 2470 feet below present sea level
(Deevey, 1950 and therein). The configuration of the west coast, with
numerous embayed river mouths, submerged channels in the Gulf, and
labyrinthine island groups, attests to the subsidence.
Archeology also provides some evidence of recent subsidence along
the Florida west coast. On the eastern shores of the state, from Vero
Beach northward, are numerous shell middens-Indian refuse heaps-
dating from what archeologists call the Mt. Taylor and Orange periods
(Goggin, 1952; Rouse, 1951). During the Mt. Taylor period pottery
manufacture was unknown to the Indians, while during the Orange
period a characteristic fiber-tempered ware was made. When Willey
(1949) surveyed the archeology of the Florida Gulf Coast, he was
unable to recognize or define any local period comparable to Mt.
Taylor or Orange in age; all the sites were of later date. Middens on
the present west coast all postdated the use of fiber-tempered pottery.
Yet it seemed likely that the west coast was inhabited at a time when
this ware was in use, for a few fiber-tempered potsherds had been
picked up in the area. A question therefore arose: Where are the
earlier middens of the west coast? Subsequently, west coast sites a
little later than the Orange period were found to be submerged, wholly
or in part, by the waters of the Gulf (Bullen and Bullen, 1950, 1953).
This led to the speculation that the still older sites were now well be-
neath low tide mark. A submerged site, apparently preceramic and
therefore comparable to Mt. Taylor middens in age, was eventually
found off the coast of Pinellas County; and flint chipping of uncertain
age was found as much as two miles offshore (Neill, MS b). At one
locality there was a sort of "horizontal stratigraphy," with early Indian
artifacts well out in the water, later ones near what is now high tide
mark, and still later ones along the present supratidal dunes (idem).
There is some partial submergence of middens and mounds on the
east coast, attributable to the postglacial rise of sea level (Goggin, 1948;
Rouse, 1951), but in that area there appears to be nothing comparable
to the wholesale drowning of early sites along the Gulf Coast. Of
course, mere rise of sea level would affect both coasts equally, and it
is therefore reasonable to presume that the west coast has also ex-
perienced land subsidence within the period of Indian occupancy.
BULLETIN FLORIDA STATE MUSEUM
Much more study is needed; but at any rate the archeological evidence
is consistent with geological opinion.
The depression of the west coast is of biogeographic significance.
Today, miles out from this coast the Gulf is still very shallow. A num-
ber of distinctive west coast organisms may once have ranged over
an extensive territory now largely submerged. I refer to the little
mole (Scalopus aquaticus parvus), the Florida big brown bat (Eptesicus
fuscus osceola), the Suwannee turtle (Pseudemys floridana suwannien-
sis), the Gulf Hammock rat snake (Elaphe obsoleta williamsi), the Gulf
Hammock mud siren (Pseudobranchus striatus lustricolus), a euphorbia
(Phyllanthus platylepis) and a quillwort (Isoetes alata). Further geo-
logical studies on west coast subsidence may throw light on speciation
along what is now the western edge of the peninsula. At any rate, had
it not been for this subsidence, the Cedar and Anclote Keys, the long
chain of west coast islands from Caladesi to Estero, the Ten Thousand
Islands, the Florida Keys, the Marquesas group, and the numerous
specks of land in Florida Bay would all be part of the mainland; for
all of these islands are separated from the mainland by water less
than three fathoms deep. The populations of the cottonmouth (Agkis-
trodon piscivorus) and of the southeastern five-lined skink (Eumeces
inexpectatus) on the islands in Suwannee Sound; those of the Carolina
anole (Anolis carolinensis), the ground skink (Lygosoma laterale), and
of a rat snake (Elaphe guttata subspecies) in the Marquesas group; of
the six-lined racerunner (Cnemidophorus sexlineatus) on Boca Grande;
and of the gopher tortoise (Gopherus polyphemus) on Caladesi, may
in some cases reflect this subsidence.
The depression of the west coast may explain another and hitherto
puzzling circumstance: the occurrence of many organisms on the
southern Florida mainland and on the lower Keys, but not on the
upper Keys. The Miami odlite is the foundation for the lower Keys,
the southern mainland, and the islands in Florida Bay; whereas the
upper Keys are based on a coral reef, the Key Largo formation, which
grew apparently in the Pamlico sea (Cooke, 1939, 1945). Mainland
species could have moved overland into what is now the lower Keys
probably before the upper Keys appeared above water. Today the
white-tailed deer (Odocoileus virginianus), the cotton rat (Sigmodon
hispidus), the ribbon snake (Thamnophis sauritus), a glass lizard (Ophi-
saurus species) the striped mud turtle (Kinosternon bauri), the leopard
frog (Rana pipiens), the southern toad (Bufo terrestris), and the oak
toad (B. quercicus) occur on the lower Keys and the southern main-
land, but not on the upper Keys. The cricket frog (Acris gryllus) may
be added if an old Key West record is valid. A pine (Pinus caribaea),
NEILL: BIOGEOGRAPHY OF FLORIDA
the sawgrass (Mariscus jamaicensis), the cabbage palm (Sabal pal-
metto) and the waxmyrtle (Myrica cerifera), common to the mainland
and the lower Keys, are lacking from most or all of the upper Keys
(Alexander,, 1958; Harper, 1927).
DISTRIBUTION AND PAST PERIODS OF Low RAINFALL
The Pleistocene was characterized by fluctuations of rainfall. It
has been suggested that increased precipitation, in some cases abetted
by glacial chilling, once brought into Florida certain organisms which
today are considered essentially upland or northern. The possible
effects of a decrease in rainfall may now be considered.
The forests of eastern North America are replaced farther west by
grassland. The amount of precipitation determines the nature of
the plant climax, and a shift toward a drier climate would cause the
grassland, and perhaps other western associations, to extend farther
east than they do at present. In the past there have been such east-
ward extensions of a grassland or western biota (Deevey, 1949; Frey,
1951; Grobman, 1941; Hurt, 1958; Schmidt, 1989; Transeau, 1935).
Fingers of grassland have at times extended into Ohio, Indiana, Michi-
gi. Pennsylvania, and New York, bringing with them some animal
species. Today, communities of prairie plants occur at isolated locali-
ties as far east as northwestern Pennsylvania and as far south as the
Highlands Rim in Kentucky and Tennessee. The Black Belt of the
Alabama coastal plain also supports an extensive prairie flora. Prior
to settlement, portions of this belt were naturally treeless and thor-
oughly prairielike (Harper, 1943). One eastward extension of the
grassland took place during the so-called climatic optimum, which
lasted roughly from 7500 to 5000 years ago. However, the entry of a
"western element" into Florida probably took place long before then;
for in some cases remains of "western" organisms occur in older, Pleis-
tocene deposits of the state. Pollen profiles from Lake Singletary,
North Carolina, revealed a stratum characterized by grasses, com-
posites, and sedges, with but few trees; and this stratum, implying
grassland conditions, underlay the fir-spruce-pine stratum of the cold
Mankato (Frey, 1951). There may have been several long periods of
decreased rainfall during the Pleistocene, and western organisms may
have invaded the east on a number of occasions.
Several western or grassland animals occur in the late Pleistocene
of Florida, and a few essentially western species inhabit the state
today. Pleistocene deposits in Florida have yielded remains of an
extinct bison, horses, cameloids, and elephants, thought to have been
BULLETIN FLORIDA STATE MUSEUM
grassland species, and some large carnivores, thought to have preyed
on the grazing animals. There were two armadillos, a coyote virtually
identical with the modern one, a pocket gopher perhaps allied to the
present western ones, and a peccary related to the species which today
ranges into the southwestern United States (Gazin, 1950; Sherman,
1952; Simpson, 1929). There was a bear of the genus and subgenus
Ursus (Gazin, 1950); within historic times this group ranged in the
New World only from Alaska into Mexico. There was a jaguar per-
haps slightly different from the present-day one; and a smaller cat,
either the margay or the jaguarundi (idem). These felines are some-
times thought of as being tropical, but they also inhabit scrub country
of the western United States (Hock, 1955). The Pleistocene avifauna of
Florida included a few western species, the most impressive being the
California condor or rather its Pleistocene ancestor (Wetmore, 1931).
Today the western element is typified by the Florida jay (Aphelo-
coma c. caerulescens). This bird, confined to rosemary scrub areas of
the peninsula, is nearly identical with certain jays found from Texas
westward. The restriction of this jay to scrub is interesting; there are
a number of similarities between Florida scrub and some western
habitats (Sutton, 1949). Another western species in the state is the
burrowing owl (Speotyto cunicularia). One race of this bird ranges
no farther cast than the Great Plains; another is confined to peninsular
Florida. The Florida burrowing owl inhabits a situation locally called
"prairie": flat or gently undulating land, virtually treeless, covered with
low grasses and forbs, and dotted with clumps of saw-palmetto and
other shrubs. In the upper part of the peninsula it inhabits cleared,
grassy rangeland (Neill, 1954a). Ornithologists have mentioned the
black-necked stilt (Himantopus mexicanus) as one of the western birds
in Florida, but its extremely wide distribution renders its presence in
Florida unimpressive. One race of the sandhill crane (Grus canaden-
sis) inhabits Florida, while the other races are western. The duck
Anas fulvigula occurs as two populations, one race being endemic,to
Florida while the other is found in southern Louisiana and Texas. A
race of the caracara (Caracara cheriway), confined in Florida to the
peninsula, is identical with that occurring from Texas and Baja Cali-
fornia to Central America (Sprunt, 1954). Perhaps the indigo snake
(Drymarchon corals) should be mentioned here. One race of this
species ranges northward from Mexico into south-central Texas. East-
ward of this area no indigo snakes are found until one 'reaches the
western end of the Florida panhandle, where there is a disjunct popu-
lation. Another population, perhaps disjunct, inhabits southern Geor-
gia; and the species is fairly common throughout much of peninsular
NEILL: BIOGEOGRAPHY OF FLORIDA
Florida. The case parallels that of the Florida jay, except that the
snake has one or two relic populations along the route of eastward
migration. A gap in the route may be filled by a Pleistocene specimen
from eastern Texas; it was taken from a caliche deposit in an area
which, todhy, is too moist for caliche formation (Harrington, 1953).
Perhaps the vinegaroon or whip-tailed scorpion (Mastigoproctus
giganteus) should be listed as "western." Common from Texas and
Arizona into Mexico, it is also found in the central Florida sandhills.
Its range has been given as "Arizona to Florida" (Pratt, 1929), implying
continuity; but its comparative abundance in the peninsula is note-
Impressively "western" scenery is to be found along the relatively
dry west coast of the peninsula from the Manatee River to the lower
Keys. Here there is an association known as cactus thicket, composed
largely of stiff, crooked, spiny shrubs. These include several genera
of cacti, some of the plants up to 20 feet tall; huge centuryplants
(Agave); yucca; a coralbean (Erythrina arborea); wait-a-bit (Guilandina
crista); and cock-spur (Pisonia aculeata). A number of these plants
occur also in southern Texas and Mexico (Harper, 1927; Small, 1933).
The association has been called "the most remarkable natural cactus-
garden east of the western American deserts" (Small, 1921, p. 51). A
common grass of the region, Monanthochloe littoralis, likewise occurs
in southern Texas and Mexico. Some of these plants may be relics
of an early invasion from the west during a dry period, surviving today
in an area where relatively low rainfall and soil porosity produce ex-
tremely arid conditions.
It may be significant that some western organisms, recently intro-
duced, seem to thrive in rosemary scrub and high pine of interior
Florida, as well as on sandy coastal islands of the state. The armadillo
(Dasypus novemcinctus) and the Texas horned lizard (Phrynosoma
cornutum) are noteworthy in this regard (Allen and Neill, 1955a; Neill,
THE SUPPOSED "SouTH AMERICAN ELEMENT"
Certain authors, remarking on a "South American element" among
the Pleistocene mammals of Florida and nearby areas, have suggested
that tropical conditions once prevailed in the southeastern United
States. However, many South American animals are not tropical; and
some of them belong to groups that originated in North America and
subsequently spread. Furthermore, the South American element is
comprised mostly of extinct species, and the majority represent extinct
genera. One cannot even speculate about the temperature and mois-
206 BULLETIN FLORIDA STATE MUSEUM Vol. 2
ture requirements of such animals; efforts to do so will not withstand
analysis. For example, tapirs of the genus Tapiius occurred in the
Pleistocene of Florida; and a surviving species of Tapirus is Neotropi-
cal. However, the genus ranges in time from the upper Miocene to
the present day, and in space from North and South America to Asia
and Europe. One could hardly derive any climatic data from the
presence of Tapirus in the Florida Pleistocene. Most of the South
American element are equally useless as indicators of past climatic
conditions, although we might draw some conclusions from those
species that are still in existence. All of these, while occurring in tropi-
cal situations, also inhabit dry, brushy country of the southwestern
THE TROPICAL ELEMENT IN FLORIDA
The present climate of the coastal plain in the southeastern United
States appears to be suitable for many tropical organisms, once they
are introduced. Thus, the axis deer is spreading in Florida east of
the St. Johns River (Allen and Neill, 1954); the sambar deer has done
well on St. Vincents Island near the mouth of the Apalachicola (idem;
Newman, 1948); there are two colonies of rhesus monkeys in Marion
County; the nutria is well established in parts of the southeast (Dozier,
MS) and has been collected in the Florida panhandle; the cattle egret
seems destined to spread widely in North America (Sprunt, 1953,
1954); the greenhouse frog of Cuba is now common in Florida at least
as far north as Alachua County (Goin, 1947); the water-hyacinth has
been overly successful in a number of southern states and especially
in Florida (Weeks and Bissland, 1949).
So far as I can see, the only tropical element to reach Florida with-
out man's aid did so across water, from the West Indies. The climax
community of extreme southern Florida is tropical hammock, dom-
inated by such West Indian species as Jamaica dogwood, poisonwood,
lignumvitae, mastic, and mahogany. Other tropical plants, appar-
ently native to southern Florida as well as to the Caribbean islands,
include the trema, papaya, potato tree, lantanas, gumbo-limbo, stop-
pers (Eugenia), strangler-figs, wild tamarind, soapberry, bustic (Diph-
olis), thatch palms, crabwood, lancewood, manchineel, Paradise tree,
fiddlewood, satinleaf, wild coffee (Psychotria), and rough velvetseed
'The biogeographer need not try to fit the jaguar and the porcupine into the
same ecological picture. Pleistocene deposits in Florida are not necessarily all of
the same age. They have faunal differences; and fluctuations of climate might
have brought species into or out of Florida within a short time, geologically
NEILL: BIOGEOGRAPHY OF FLORIDA
(Guettarda). A few tropical plants have produced distinctive forms
in southern Florida (and some of the temperate, central Florida species
have done likewise). Thus the subtropical portion of the state is an-
other area .of endemism in plants (Davis, 1943; Harper, 1927, 1949;
Small, 1933). However, as noted previously, Florida has no really
impressive endemic flora of tropical affinities; and it seems likely that
the present West Indian floral element moved into the state since
Wisconsin times (Dillon, 1956).
Tropical birds, currently or until recently breeding in southern
Florida, include the Everglades kite (Rostrhamus sociabilis), the short-
tailed hawk (Buteo brachyurus), the reddish egret (Dichromanassa
rufescens), the scarlet ibis (Eudocimus ruber), the roseate spoonbill
(Ajaia ajaia), the flamingo (Phoenicopterus ruber), the eastern white-
winged dove (Zenaida asiatica), Maynard's cuckoo (Coccyzus minor),
the black-whiskered vireo (Vireo altiloquus), and the white-crowned
pigeon (Columba leucocephala) (Sprunt, 1954). Numerous other
tropical birds, such as the emerald hummingbird, the Bahama honey
creeper, and Bahama grassquit, have turned up in Florida as accidental
visitors or wanders, especially after storms. Two tropical bats (Eu-
mops glaucinus and Artibeus jamaicensis) have also appeared in the
state (Sherman, 1952). A tropical bird, the smooth-billed ani (Crotoph-
aga ani), recently changed its Florida status from casual visitor to
breeding resident. Other tropical organisms native to southern Flor-
ida and parts of the Caribbean include the West Indian seal (Monachus
tropicalis), which is almost extinct, and no longer to be found in Flor-
ida waters; a crocodile (Crocodylus acutus); and the reef gecko
(Sphaerodactylus notatus). A common Caribbean anole (Anolis sagrei)
apparently has been in Florida for a long while, having produced a
race on Key West (Oliver, 1948).
Several tropical amphibians and reptiles, mostly of West Indian
origin, are now established in southern Florida. A few of these may
have arrived by waiting, but most were introduced by man. Included
are three Neotropical frogs, as well as 10 Neotropical lizards and a
Mediterranean one.5 The success of these species in southern Florida
may reflect the presence of tropical habitats in that area, unoccupied
Neotropical introductions are: Lizards-Sphaerodactylus notatus, S. cinereus,
S. argus, Gonotodes fuscus, Leiocephalus carinatus, Anolis s. sagrei, A. s. ordinatus,
A. distichus subspecies, A. equestris, Ameiva ameiva. Frogs-Eleutherodactylus
ricordi planirostris, Hyla septentrionalis, Bufo marines. The Mediterranean lizard
Hemidactylus turcicus is introduced. Of these, A. equestris, Ameiva, and Bufo
have not been mentioned in the literature.
BULLETIN FLORIDA STATE MUSEUM
by reptiles and amphibians of temperate stocks. Various tropical
plants, deliberately imported by man, now grow wild in Florida.
Perhaps the distribution of many Florida organisms could be ex-
plained solely in terms of present-day environmental conditions. This
is particularly true of species which readily disseminate themselves
and for which the old Pleistocene barriers are no longer significant.
For example, a plant with airborne seeds might take root anywhere
that climatic, edaphic, and biotic conditions permit. The distribution
of such a species is a matter for the biogeographer whose approach is
largely ecological. There remain, however, numerous Florida plants
and animals whose present ranges apparently reflect not only the en-
vironmental conditions of today but also the geologic and climatic
events of past ages.
In consequence, one might recognize seven biogeographic areas of
Florida, some much better defined than others. These are (1) the
western panhandle; (2) the Apalachicola drainage; (3) the remainder
of the panhandle, not markedly different from adjoining portions of
the Gulf coastal plain in Alabama and Georgia; (4) northeastern Flor-
ida, but slightly differentiated from the lower Atlantic coastal plain
of Georgia; (5) the central Florida highlands; (6) the Gulf Hammock;
and (7) the subtropical tip of the peninsula. It should be noted that in
most cases these areas are bounded not by lines but by fairly wide
zones of transition or of commingling, perhaps because many of the
Pleistocene barriers to distribution no longer exist.
It should also be noted that the biogeographic conclusions reached
herein are tentative. The intriguing problems of biogeography require
for their solution the services of collectors, taxonomists, paleontologists,
geologists, ecologists, archeologists, palynologists, climatologists, and
others. If the present trend toward compartmentalization of knowl-
edge be deemed inevitable, then let me end with a plea for interdis-
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BULLETIN FLORIDA STATE MUSEUM
ROGERS, J. SPEED
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1953. Newcomer from the Old World. Audubon Mag., 55 (4): 178-181.
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1935. The prairie peninsula. Ecology, vol. 16, no. 3, pp. 423-437.
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BULLETIN FLORIDA STATE MUSEUM
TRASK, P. D., F. B. PHLEGEB, and H. C. STETSON
1947. Recent changes in sedimentation in the Gulf of Mexico. Science, vol.
106, pp. 460-461.
U.S. DEPARTMENT OF AGRICULTURE
1941. Climate and man. Washington, pp. i-xii, 1-1248.
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VAN DER SCHALIE, HENRY
1940. The naiad fauna of the Chipola River, in northwestern Florida. Lloydia,
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VANZOLINI, PAULO E.
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1949. Insects from burrows of Peromyscus polionotus. Ibid., vol. 32, no. 2,
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YOUNG, F. N., and C. C. GOFF
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