<%BANNER%>

Reproductive Demography of the Scleractinian Coral Siderastrea radians in the St. Martins Keys, Florida

Permanent Link: http://ufdc.ufl.edu/UFE0022691/00001

Material Information

Title: Reproductive Demography of the Scleractinian Coral Siderastrea radians in the St. Martins Keys, Florida Spatial Patterns in Abundance, Size, and Reproductive Characteristics
Physical Description: 1 online resource (85 p.)
Language: english
Creator: Lazar, Katherine
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: abundance, aggregation, coral, florida, puberty, reproduction, scleractinian, sexuality, siderastrea, size, variation
Fisheries and Aquatic Sciences -- Dissertations, Academic -- UF
Genre: Fisheries and Aquatic Sciences thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The reproductive demography of corals is reported to play a significant role in their population dynamics by influencing reproductive success. The objectives of this study were to quantify spatial variation in: (1) density, (2) aggregation, (3) size distribution, (4) sexuality, (5) puberty size, and (6) sex ratio in a population of Siderastrea radians in the St. Martins Keys, Florida (SMK). Initially, corals were counted and measured at each of 81 sites arrayed in a 16-km^2 grid during 2006 and 2007. Results indicated that corals were distributed in patches (mean Morisita's Index = 3.74; range = 0.00-10.00), with densities ranging from 0.0 to 86.0 individuals m^?2 (mean = 7.0 colonies m^2) in both years. The size-frequency distributions were positively skewed like many other scleractinian populations, with the majority of individuals falling within the smallest size classes. To quantify the relationships among density, aggregation, and sex ratio, corals were collected from 10 sites with different combinations of density and aggregation in June 2007. Histological data suggested a gonochoric population, however, planulae were not observed in histological sections; therefore, a brooding reproductive mode in the SMK populations could not be confirmed. Colonies reached puberty at approximately 32 mm maximum diameter and formed aggregations with sex ratios of approximately 1:1 at scales of tens and hundreds of meters. In contrast, a puberty size of 20 mm and a female-biased sex ratio have been reported for Caribbean populations. Statistically significant linear regressions showed that numbers of solitary polyps (i.e., recruits) increased with numbers of conspecifics and putative adults, although the relationship with adults was weaker, which indicated that planulae may settle and/or survive better near conspecifics and disperse at least tens of meters from their parental colonies. Overall, these results pointed to geographic differences in reproductive characteristics across the range of S. radians.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Katherine Lazar.
Thesis: Thesis (M.S.)--University of Florida, 2008.
Local: Adviser: Frazer, Tom K.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2009-02-28

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022691:00001

Permanent Link: http://ufdc.ufl.edu/UFE0022691/00001

Material Information

Title: Reproductive Demography of the Scleractinian Coral Siderastrea radians in the St. Martins Keys, Florida Spatial Patterns in Abundance, Size, and Reproductive Characteristics
Physical Description: 1 online resource (85 p.)
Language: english
Creator: Lazar, Katherine
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: abundance, aggregation, coral, florida, puberty, reproduction, scleractinian, sexuality, siderastrea, size, variation
Fisheries and Aquatic Sciences -- Dissertations, Academic -- UF
Genre: Fisheries and Aquatic Sciences thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The reproductive demography of corals is reported to play a significant role in their population dynamics by influencing reproductive success. The objectives of this study were to quantify spatial variation in: (1) density, (2) aggregation, (3) size distribution, (4) sexuality, (5) puberty size, and (6) sex ratio in a population of Siderastrea radians in the St. Martins Keys, Florida (SMK). Initially, corals were counted and measured at each of 81 sites arrayed in a 16-km^2 grid during 2006 and 2007. Results indicated that corals were distributed in patches (mean Morisita's Index = 3.74; range = 0.00-10.00), with densities ranging from 0.0 to 86.0 individuals m^?2 (mean = 7.0 colonies m^2) in both years. The size-frequency distributions were positively skewed like many other scleractinian populations, with the majority of individuals falling within the smallest size classes. To quantify the relationships among density, aggregation, and sex ratio, corals were collected from 10 sites with different combinations of density and aggregation in June 2007. Histological data suggested a gonochoric population, however, planulae were not observed in histological sections; therefore, a brooding reproductive mode in the SMK populations could not be confirmed. Colonies reached puberty at approximately 32 mm maximum diameter and formed aggregations with sex ratios of approximately 1:1 at scales of tens and hundreds of meters. In contrast, a puberty size of 20 mm and a female-biased sex ratio have been reported for Caribbean populations. Statistically significant linear regressions showed that numbers of solitary polyps (i.e., recruits) increased with numbers of conspecifics and putative adults, although the relationship with adults was weaker, which indicated that planulae may settle and/or survive better near conspecifics and disperse at least tens of meters from their parental colonies. Overall, these results pointed to geographic differences in reproductive characteristics across the range of S. radians.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Katherine Lazar.
Thesis: Thesis (M.S.)--University of Florida, 2008.
Local: Adviser: Frazer, Tom K.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2009-02-28

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022691:00001


This item has the following downloads:


Full Text

PAGE 1

1 REPRODUCTIVE DEMOGRAPHY OF THE SCLERACTINIAN CORAL Siderastrea radians IN THE ST. MARTINS KEYS, FLORIDA: SPA TIAL PATTERNS IN ABUNDANCE, SIZE, AND REPRODUCTIVE CHARACTERISTICS By KATHERINE ELIZABETH LAZAR A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2008

PAGE 2

2 2008 Katherine Elizabeth Lazar

PAGE 3

3 To Duncan Vaughan

PAGE 4

4 ACKNOWLEDGMENTS I would lik e to thank my committee: Tom Frazer, Chuck Jacoby, Colette St. Mary, and Bill Lindberg. I would also like to thank the following for assist ance in the field: Don Behringer, Aaron Bunch, Matt Catalano, Loreto De Brabande re, Nikki Dix, Kristin Dormsjo, Emalee Heidt, Stephanie Keller, Matt Lauretta, Lauren Marc inkiewicz, Doug Marcinek, Emily Mitchem, Meredith Montgomery, Kelly Robinson, Darlen e Saindon, and Duncan Vaughan. Krista McCoy assisted with histological techniques. This project was made possible through FWC special activity license #06SRP-1005.

PAGE 5

5 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........7 LIST OF FIGURES.........................................................................................................................8 ABSTRACT...................................................................................................................................10 CHAP TER 1 GENERAL INTRODUCTION.............................................................................................. 12 2 SPATIAL PATTERNS IN AB UNDANCE AND SIZE OF Siderastrea radians .................16 Introduction................................................................................................................... ..........16 Materials and Methods...........................................................................................................19 Study Site..................................................................................................................... ....19 Population Survey........................................................................................................... 19 Statistical Analyses.......................................................................................................... 20 Results.....................................................................................................................................21 Colony Size.....................................................................................................................21 Colony Abundance..........................................................................................................22 Patterns in Aggregation................................................................................................... 23 Discussion...............................................................................................................................23 Conclusions.....................................................................................................................27 3 REPRODUCTIVE CHARACTERISTICS OF Siderastrea radians ......................................37 Introduction................................................................................................................... ..........37 Materials and Methods...........................................................................................................43 Coral Surveys..................................................................................................................43 Coral Collection...............................................................................................................44 Histological Analysis....................................................................................................... 45 Sex Ratio.........................................................................................................................46 Puberty Size.....................................................................................................................46 Distribution of Recruits Relative to Conspecifics ........................................................... 47 Results.....................................................................................................................................47 Coral Surveys..................................................................................................................47 Reproductive Strategy..................................................................................................... 48 Sex Ratio.........................................................................................................................48 Puberty Size.....................................................................................................................49 Distribution of Recruits Relative to Conspecifics ........................................................... 50 Discussion...............................................................................................................................50 Sexuality..........................................................................................................................51 Sex Ratio.........................................................................................................................52

PAGE 6

6 Puberty Size.....................................................................................................................54 Reproductive Mode.........................................................................................................56 Distribution of Recruits Relative to Conspecifics ........................................................... 58 Conclusions.....................................................................................................................61 4 GENERAL CONCLUSIONS................................................................................................. 75 LIST OF REFERENCES...............................................................................................................77 BIOGRAPHICAL SKETCH.........................................................................................................85

PAGE 7

7 LIST OF TABLES Table page 2-1 Environmental conditions at four samp ling stations near the Hom osassa River and the St. Martins Keys...........................................................................................................28 2-2 Results of two-way ANOVA using log10(coral counts + 1).............................................. 28 2-3 Evidence of partial colony mortality due to bleaching, encrustation by algae and/or sponge, and presence of sedim ent for Siderastrea radians colonies in the St. Martins Keys...................................................................................................................................28 3-1 Densities and Morisitas Indices based on pooled data from 2006 and 2007 for sites selected for coral surveys in June 2007............................................................................. 62 3-2 Reproductive characteristics of Siderastrea radians colonies at the 10 coral collection sites. .............................................................................................................. .....62 3-3 Frequency of fertile Sid erastrea radians colonies by size class........................................63 3-4 Densities, Morisitas Indices (I), and density and aggrega tion classes (H: high; L: low) based on surveys of Siderastrea radians colonies in 24 quadrats at each of 10 sites.......................................................................................................................... ..........63 3-5 Results of 2-way ANOVA using ratios of num bers of males to numbers of females....... 63

PAGE 8

8 LIST OF FIGURES Figure page 2-1 St. Martins Keys, Florida, showi ng study sites for the 2006 and 2007 surveys. ............... 29 2-2 Sampling stations for environmental da ta (m odified from Jacoby et al. 2008)................. 30 2-3 Linear regression of Siderastrea radians colony heights vs. m aximum diameters........... 31 2-4 Size-frequency distributions of Siderastrea r adians colonies in 2006 and 2007..............32 2-5 Back-transformed mean counts of Siderastrea radians colon ies 95% confidence limits (CL).................................................................................................................... ......33 2-6 Mean densities of Sidera strea radians (colonies m2) in 2006......................................... 34 2-7 Mean densities of Sidera strea radians (colonies m2) in 2007......................................... 35 2-8 Mean densities of Sidera strea radians (colonies m2) for 2006 and 2007........................ 36 3-1 Mean densities of Sidera strea radians (colonies m2) from surveys in June 2007........... 64 3-2 Size-frequency distribution for Siderastrea radians colonies sam pled in June 2007.......65 3-3 Mean densities of Siderastrea radians and Morisitas Indic es from coral surveys in June 2007...........................................................................................................................66 3-4 Size-frequency distribution of Siderastrea radians colonies collected for histology........ 67 3-5 Classes of density and aggregation (based on M orisitas Indices) for July August 2007 coral collection sites.................................................................................................. 68 3-6 Percent of mature male and female Siderastrea radians colonies across differing densities and degrees of aggregation.................................................................................69 3-7 Mean ratios of male to female Siderastrea radians standa rd errors (SE) as measured across differing densities and degrees of aggregation....................................... 70 3-8 Cumulative frequency distributions for non-reproductive, female, and m ale Siderastrea radians colonies vs. maximum diameters...................................................... 71 3-9 Linear regression of numbers of Siderastrea radians recruits (solitary polyps) vs. total num bers of all other conspecifics.............................................................................. 72 3-10 Linear regression of numbers of Siderastrea radians recruits (solitary polyps) vs. num bers of conspecifics 32.8 mm in maximum diamet er (mature colonies)................. 73

PAGE 9

9 3-11 Linear regression of numbers of Siderastrea radians recruits (solitary polyps) vs. nu mbers of conspecifics < 32.8 mm in ma ximum diameter (immature colonies)............. 74

PAGE 10

10 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science REPRODUCTIVE DEMOGRAPHY OF THE SCLERACTINIAN CORAL Siderastrea radians IN THE ST. MARTINS KEYS, FLORIDA: SPA TIAL PATTERNS IN ABUNDANCE, SIZE, AND REPRODUCTIVE CHARACTERISTICS By Katherine Elizabeth Lazar August 2008 Chair: Thomas K. Frazer Major: Fisheries a nd Aquatic Sciences The reproductive demography of corals is re ported to play a signi ficant role in their population dynamics by influenci ng reproductive success. The object ives of this study were to quantify spatial variation in: (1 ) density, (2) aggregation, (3) si ze distribution, (4) sexuality, (5) puberty size, and (6) se x ratio in a population of Siderastrea radians in the St. Martins Keys, Florida (SMK). Initially, corals were counted and measured at each of 81 sites arrayed in a 16-km2 grid during 2006 and 2007. Results indicated that corals were distributed in patches (mean Morisitas Index = 3.74; range = 0.00 10.00), with densities ranging from 0.0 to 86.0 colonies m (mean = 7.0 colonies m2) in both years. The size-frequency distributions were positively skewed like many ot her scleractinia n populations, with the majority of colonies falling within the smallest size clas ses. To quantify the relationships among density, aggregation, and sex ratio, corals were collected from 10 sites w ith different combinations of density and aggregation in JulyAugust 2007. Histological data suggested a gonochoric population; however, planulae were not observed in histological sections. Therefore, a brooding reproductive mode in the SMK popula tions could not be confirmed. Colonies reached puberty at approximately 32 mm maximum diameter and fo rmed aggregations with sex ratios of

PAGE 11

11 approximately 1:1 at scales of tens and hundreds of meters. In contrast, a puberty size of 20 mm and a female-biased sex ratio have been re ported for Caribbean populations. Statistically significant linear regressions showed that numbers of solitary polyps (i.e., recruits) increased with increasing numbers of conspecifics, coloni es above puberty size (putative adults), and colonies below puberty size. The relationship with adults was weakest, which indicated that 1) planulae may settle and/or survive better near conspecifics and 2) planulae are likely to disperse at least tens of meters from their parental colonies. Overall, these results pointed to geographic differences in reproductive characteristics ac ross the range of S. radians

PAGE 12

12 CHAPTER 1 GENERAL INTRODUCTION Contem porary research on scler actinian corals is dominated by efforts to elucidate the causes and consequences of a worldwide dec line in coral cover (B ellwood et al. 2004). Accordingly, it is imperative for scientists a nd managers to understand how corals and coral reefs respond to environmental and physical distur bance. A demographic a pproach is well-suited to address this issue (Bak & Meesters 1999, M eesters et al. 2001, Ed munds 2005). Demographic research on populations of corals centers on de termining numbers, sizes and/or ages, and distributions of recruits and a dults of both sexes, and ultimate ly, it includes spatiotemporal changes in response to changes in key demogr aphic rates (i.e., birth, death, immigration, and emigration). An understanding of the status and changes in th e demography of a population has insight into the reproductive ecology of a species as part of its foundation. Reproductive demography, defined here as the spatial analys is of reproductive ecol ogy, contributes to an understanding of interactions between reproductive ecology and population-level processes that result in a population structure at any given point in time. Th e reproductive strategy employed by a species, including sexuality and reproductive mode that come to be reflect ed in sex ratios and distributions of sexes, interacts with pre-sett lement and post-settlement processes that affect reproductive output, growth, survival, and subseque nt reproduction to ultimately result in an observed population structure. Fo r example, the spatial distri bution of sexes in a population directly affects fertilization success leading to an indirect effect on recruitment rates. Accordingly, research on responses to distur bance by corals and coral reefs is incomplete without data on both population stru cture and the reproductive charac teristics of the species of interest.

PAGE 13

13 The species of interest in this study is Siderastrea radians commonly known as the lesser starlet coral. This purpor ted brooder (Szmant 1986, Soong 1991) is common throughout the tropical Atlantic, and it is found in highly dynamic environments tolerated by few other scleractinian corals (Lewis 1989, Lirman et al 2002, Lirman et al. 2003, Moses et al. 2003). For example, in a decade-long study in St. John, U.S. Virgin Islands, small, morphologically simple species such as S. radians became relatively more abundant in areas exposed to higher temperatures in contrast to larger, more complex reef-building species such as Porites astreoides and P. furcata (Edmunds 2004). These observed changes in coral community structure appeared to be linked to higher mean seaw ater temperature and fewer cold days, and they resulted from enhanced recruitment of S. radians and depressed growth rates of Porites Agaricia and Favia (Edmunds 2004). Furthermore, anecdotal evidence suggests that, among scleractinian species in the Florida Keys, S. radians is usually one of the last to bleach (M. Johnson, The Nature Conservancy, pers. comm.). In general, Siderastrea radians and other smaller, morphologically simple species may outcompete or simply survive better than larger, more structurally complex corals such as P. astreoides and P. furcata (Edmunds 2004). The relative success of S. radians may be due to its B5a clade of symbiotic z ooxanthellae (LaJeunesse 2002), which is known to tolerate temperatures up to 36C (W arner et al. 1996). Zooxanthellae in Symbiodinium clade B are typically found in shallow-wate r corals and in portions of la rge colonies that receive high irradiance (Rowan & Knowlton 1995). Reproduc tive mode and a spherical morphology also promote the survival of S. radians Lewis (1989) showed that in tide pools and on reef flats where wave action was strong, the survival of S. radians increased with colony size and was positively correlated with development of a spheri cal shape. Because sexu al reproduction is its primary mode (Duerd en 1904, Vermeij 2005), S. radians also may adapt more easily during

PAGE 14

14 periods of environmental fluctuation (Laske r & Coffroth 1999). Many scleractinian species reproduce primarily asexually, i. e., they depend on processes such as budding, fragmentation, and fission for colony growth and propagation (Hughes et al. 1992). Asexual reproduction may be advantageous in physically stab le environments, but the absence of genetic variability leaves a large proportion of a genetically uniform popula tion vulnerable to physical and/or biological stress (Richmond 1997, Lasker & Coffroth 1999). Further, fragments and other asexually produced tissues have limited dispersal capabilities, in contrast to most gametes and/or larvae (Richmond 1997). Enhanced genotypic diversit y associated with sexual reproduction may decrease a species susc eptibility to extinction, augmenting persistence of a species following environmental disturbance or climate change (Richmond 1997). Although the SMK population of Siderastrea radians does not build reefs, it offers a tractable opportunity to gain insights into in teractions between repr oductive and demographic characteristics. There is little scientific literature specific to S. radians (but see Duerden 1904, Szmant 1986, Soong 1991, Vermeij 2005), and none on th is particular population. Therefore, a study of its reproductive demogra phy both adds to the body of know ledge about this species and allows comparisons across geogr aphically disjunct populations. In the face of global climate change and in creasing anthropogenic impacts on marine ecosystems, knowledge of the structure and function of coral communities is imperative if we are to assess impacts and attempt restoration. In th e following chapters, intended to stand alone, I detail a multifaceted study of the coral Siderastrea radians in the St. Martins Keys, characterize patterns in abundance and aggreg ation, and combine these data with information on sexuality, puberty size, and sex ratio derived from histology. Information on abundance, distribution, and reproductive characteristics is integral to a more complete understanding of the population

PAGE 15

15 dynamics of coral species. Many corals exhibit variation in these charact eristics across their geographic range; accordingly, it is important to understand how co ral populations are structured in a variety of locations to determine how they will respond to st ressors and other perturbations in different environments. Data that combines both demographi c and reproductive information is therefore necessary and relevant to the mana gement and conservation of coral resources.

PAGE 16

16 CHAPTER 2 SPATIAL PATTERNS IN AB UNDANCE AND SIZE OF Siderastrea radians Introduction De mographic studies are essential to further our understanding of how marine populations are structured by density-indepe ndent and density-dep endent processes operating before and after larval settlement. This portion of my study focuses on spatial patterns in key demographic parameters, i.e., abundance and si ze, for the scleractinian coral Siderastrea radians This demographic baseline expands our understanding because: (1) there is no published information on this species in the St. Martins Keys (SMK ) and limited information from other locations (Szmant 1986, Soong 1991, Lirman et al. 2003, Moses et al. 2003, Ve rmeij 2005); (2) S. radians essentially exists in a monospecific aggregation in the SMK, which is similar only to pavements of an unusual morphotype found in the Cape Ve rde Islands (Moses et al. 2003) and unlike populations in the Caribbean (Szmant 1986, Soong 1991); and (3) S. radians achieves densities in the SMK that far exceed those recorded in the Caribbean (e.g., Szmant 1986, Soong 1991, this study). Measures of the abundance and spatial distributio n of individuals, especially juveniles, can provide valuable insights into life history strate gies (Bak & Engel 1979). However, to be able to quantify these parameters, one must first decide on the unit(s) to be studied. Contemporary research on the evolutionary ecology of corals has generated debate about what comprises an individual and a population. The term individual is applied at three levels in coral biology. Firs t, the polyp constitutes a morphological individual, complete with its own mouth, gastric cavity, and gonads. Second, the colony represents a physiological individual, in that each colony functions as a separate biological unit. Lastly, all polyps and/or colonies that arise from the same zygote form a genetic

PAGE 17

17 individual, or genet. The genet may consist of polyps produced by asexual budding and separate colonies created by fragmentation. Regardless of whether a genet is scattered in space or functionally united to form a co lony, it possesses a single genotype that is subject to natural selection. In species where asexual reproducti on predominates and recruitment is highly localized, populations may consist of few genets. This fact must be recognized when studying the life histories and population dynamics of clon al organisms. However, the individual of choice ultimately depends on the question(s) being asked. Whereas studies of population genetics in corals typically con centrate on the genet, most ecological studies focus on the colony as the individual unit. Studies like this one that explore demographic parameters and reproductive characteristics at a population level use colonies almost exclusively. What, then, constitutes a population? Hughes et al. (1992) define a population as an interbreeding unit, the spatial extent and size of which is unknown for any coral. Studies on population genetics typically focus on the effective population size, Ne, which is an idealized measure of the number of genetica lly distinct individuals contribut ing genes to future generations and the evenness of those contributions. In corals, this measure is bound to be dissimilar and, in fact, typically much smaller than the standard measure of population size, N, which is obtained by counting colonies. Notwithstanding the importa nce of population genetics to the life history and reproductive strategies of a species, it is beyond the scope of this project. Additionally, Siderastrea radians reproduces primarily via sexu al reproduction (Duerden 1904, Vermeij 2005), and as this process occurs at the co lony level, it provides fu rther justification for focusing on the population as comprised of individual colonies. Although Siderastrea radians can be locally abundant, the processes that determine its distribution and abundance are not well known. B ecause adult colonies are sessile, spatial

PAGE 18

18 patterns initially are determined by the settleme nt of planulae and subsequent mortality of attached corals. Historically, the prevailing view was that la rvae of marine organisms are subjected to stochastic processe s that influence recruitment to adult populations (Caley et al. 1996). In the Caribbean, rates of recruitm ent for small brooding corals, such as Porites astreoides and Agaricia agaricites have been found to be highly spatially and temporally variable, which suggests that stoc hastic, density-independent processe s play an important role in population dynamics (Miller et al. 2000). Howeve r, variability in recruitment also may be explained by density-dependent proce sses; for example, the soft coral Efflatounaria sp. experiences increased asexual recruitment ra tes at low densities (Karlson et al. 1996). Contemporary studies focus on how density-dep endent and density-independent processes operating before and after settlement combine to structure marine populations. For example, Vermeij (2005) concluded that S. radians recruitment, i.e., the point at which newly settled polyps become visible after settlement (K eough & Downes 1982), was limited by habitat availability and structured by adult abundance in th e Florida Keys. In addition, shifts in the size structure of a coral population may result from environmental stress acting on recruitment and juvenile survival to create size-specific morta lity (see Fig. 6 in Bak & Meesters 1999). Further, changes in density of Siderastrea spp. in St. John, U.S. Virgin Islands, appeared to arise from decreased competition for space or other resour ces stemming from a decrease in the abundance of Porites, Favia and Agaricia (Edmunds 2004). Understanding the mechanisms driving patterns in the abundance and size of coral colonies is critical to developing effec tive management strategies for their long-term conservation. Such information, for example, will help predict success in new or altere d landscapes. This portion of my research focused on the population structure of Siderastrea radians in the St. Martins Keys,

PAGE 19

19 specifically spatial patterns in a bundance and colony size. This survey will yield insights into processes that structure th e population and serve as a ba seline for future studies. Materials and Methods Study Site The St. Martins Keys (S MK) are located along the north-central Gulf coast of Florida (28.5N, 82.1W), and they are contained with in the St. Martins Marsh Aquatic Preserve (SMMAP) and the Chassahowitzka National Wildlife Refuge. The study area (Fig. 2-1) comprised a dense Thalassia testudinum (turtle grass) meadow that bordered an extensive saltmarsh complex. The coral assemblage at SM K is comprised of a nearly monospecific assemblage of Siderastrea radians with a few colonies of S. siderea. The study area is subject to marked varia tions in temperature and salinity. Water temperatures at four fixed stations within a nd near the SMK ranged from 9.6 to 33.3C, with a mean of 23.1C, and salinity at these stati ons ranged from 12.0 to 36.4 ppt, with a mean of 25.06 ppt (Table 2-1, Fig. 2-2, Jac oby et al. 2008). Variation in salinity is driven primarily by tides that exhibit a semidiurna l range of approximately 1 m (G lancy et al. 2003) and discharge from nearby coastal rivers. Relatively shallow and clear water allows light to penetrate near the bottom (mean depth = 0.88 m, mean light extinction co efficient = 1.05, mean Secchi depth = 0.87 m, Table 2-1). These conditions ar e favorable for and should promote the growth of corals. Population Survey The abundances and sizes of Siderastrea radians in the SMK were quantified at 81 sites arrayed in a 16-km2 grid. Sites were identified by laying out parallel gridlines separated by 500 m on a nautical chart. In tersecting coordinates were iden tified in degrees, minutes, and seconds, and the coordinates were imported into ArcMAP (ArcINFO 9.2, Fig. 2-1).

PAGE 20

20 Between March and July 2006 and again in April and May 2007, the predetermined sites were located with a handheld global positioning sy stem (GPS 12 XL, Garmin). At each site, a 25-m transect was laid out by swimming a predet ermined, random number of kicks from the boat to a starting point and then extending a surveyors tape 25 m along a predetermined, random compass bearing. If the initial starting point and bearing put the tr ansect on land, then a new pair were chosen from the predetermined list. Ten quadrats (0.5 m x 0.5 m) were placed at random points along each transect that were chosen fr om a predetermined list. In each quadrat, the percent cover of seagrass drift algae, and attached macroalg ae was recorded before drift algae were removed. All coral colonies were subsequen tly counted and classified as comprising single or multiple polyps, and the presence of bleaching, encrustation by algae and/or sponges, and the sediment was recorded. The maximum basal diameter of each colony was measured to the nearest 0.1 mm. In 2006, heights also were recorded to the nearest 0.1 mm for colonies at 4 sites. Statistical Analyses The validity of using m aximum diameter as the sole measure of colony size was investigated by linear regression. Coral heights we re regressed against maximum diameters, with the line forced through the origin. The mean sizes of coral colonies in the tw o years of sampling were compared with a t -test. Before the analysis, data were tested for normality with a Ryan-Joiner test and homoscedasticity with Cochrans test. Data were transformed if necessary. Differences in counts of colonies were analyzed via a two-way analysis of variance (ANOVA) with Year and Site as fixed factors. Before ANOVA, data were tested for normality with a Ryan-Joiner test and homo scedasticity with Cochrans te st. Data were transformed if necessary.

PAGE 21

21 The influence of habitat was i nvestigated by relating counts of coral colonies to percent cover of seagrass, drift algae and macroalgae. Pearson product moment correlations were calculated for counts vs. each type of plant or algal coverage. The spatial distribution of col onies within sites in the SMK sampling grid was investigated using Morisitas Index of Dispersion (I), which was calculated as q ni( ni 1) I = N(N 1) (2-1) where q is the number of quadrats within a single transect, ni is the number of colonies in the ith quadrat, and N is the total number of colonies in all quadrats along a transect. If colonies are randomly distributed, the expectation is that I = 1; if colonies are uniformly distributed, I < 1; and if colonies are patchily distributed, I > 1. This index is not affected by differences in density, but the maximum possible value is determ ined by sampling effort. For example, if the number of quadrats sampled at a site is equal to 10, then the maximum value for I will be 10. Mean Morisitas Indices in the two y ears of sampling were compared with a t -test. This analysis was conducted using data from sites wh ere coral was found in both years. Before the analysis, data were tested for normality with a Ryan-Joiner test a nd homoscedasticity with Cochrans test. Data were transformed if necessary. Results Colony Size A linear regression of colony height versus m aximum diameter indicated that diameters could be used to predict heights (r2 = 0.90, p < 0.001, n = 646, Fig. 2-3). Coral colonies tended to be slightly higher than expected for hemispheres of a given maximum diameter. Diameters were used in all analyses of size.

PAGE 22

22 Size-frequency distributions from the two year s of sampling were skewed to the right as is typical of scleractinian coral species (Bak & Meesters 1998). Over 50% of the colonies had diameters less than 25 mm in both 2006 and 2007, which meant that over half of all colonies fell in the first 20% of the overall size range (Fi g. 2-4). Maximum diameters were not normally distributed or homoscedastic; therefore, the da ta were square root transformed. However, transformed data remained non-normal and heteros cedastic. Given the number of replicates, a t test for data with unequal variances was deemed sufficiently robust to these violations of assumptions. The t -test indicated that the mean sizes of coral colonies measured as maximum diameters were significantly smaller in 2006 than 2007 (t = 4.38, df = 2811, p < 0.0001). However, the mean maximum diameters di ffered by less than 3 mm (mean maximum diameter standard error for 2006 = 24.54 0.47 and for 2007 = 27.02 0.52), which did not suggest a biologically significant change in the population from one year to the next. Colony Abundance Coral colonies were found in 32 and 24 of the 81 sites in 2006 and 2007, respectively. Transform ed data [log10(count + 1)] remained non-normal, but were homoscedastic. Conservative interpretation of the two-way ANOVA indicated that co ral abundances varied among combinations of years and sites (Table 2-2). Although mean c ounts did vary between years, sites that had corals in 2006 also tended to have corals in 2007 (Fig. 2-5). Across both years, densities of Siderastrea radians ranged from 0.0 to 86.0 colonies m2. In both years, densities appeared to be concentrated on the western side of the islands, with the highest densities occurring in the southw est region of the sampling grid (Figs. 2-6 to 2-8). The mean density calculated from combined data was 7.03 colonies m2, which extrapolated to 112.48 x 106 colonies across the 16-km2 grid.

PAGE 23

23 Coral counts were significantly correlated with all three types of plant and algal coverage. Counts were negatively correlated with the percent cove r of seagrass (r = 0.38, p < 0.001) and positively correlated with percent cover of drift algae (r = 0.30, p < 0.001) and macroalgae (r = 0.14, p < 0.001). Siderastrea radians colonies typically were healt hy (Table 2-3). The incidence of bleaching in S. radians colonies was 3.29% in 2006 and 1.71% in 2007. Encrustation by algae or sponges occurred in 4.41% and 9.94% of colonies in 2006 and 2007, respectively. Sediment was found on 2.24% and 2.10% of colonies sampled in 2006 and 2007, respectively. Patterns in Aggregation Siderastrea radians in th e SMK were aggregated in both years. Values of I ranged from 0.00 to 10.00, with less than 5% of the values being less than 1.09. Log10-transformed I-values from the fifteen sites where coral was found in both years were normal and homoscedastic. A t -test indicated that mean I-values did not vary between years ( t = 0.68, df = 28, p = 0.50). The back-transformed mean for 2006 was 3.61 with lower and upper 95% confidence limits of 2.79 and 4.55, and the back-transformed mean for 2007 was 2.81 with lower and upper 95% confidence limits of 1.94 and 3.85. Discussion Results in dicated that diameters of Siderastrea radians colonies were good predictors of their heights, although colonies were not perfectly hemispherical. Therefore, maximum diameter alone should serve as a useful proxy for age. In fa ct, colony size frequently is used as a proxy for age in demographic studies of corals (Lewis 1989 ) because it is related to settlement, growth, reproduction, and mortality, which are importa nt processes that st ructure populations (Hughes 1984). The relationship between size and age does not hold true in many scleractinian corals because of partial colony mo rtality, fusion, and fission. However, S. radians appears less

PAGE 24

24 susceptible to these factors, whic h have been reco rded in only 2 3% of small colonies in the Caribbean (Lewis 1989). Indeed, evidence of partial colony mortality due to bleaching, encrustation, and/or the presence of sediment was low in the SMK, reaching levels of 9.9% and 13.7% for colonies of all sizes in 2006 and 2007, respectively. Size-frequency distributions can provide key information on the processes structuring a population. In most coral populations, the majority of colonies fall within the smallest size classes (Bak & Mees ters 1999). Results from surveys of Siderastrea radians in this study conformed to this trend, with the majority of co lonies being less than 25 mm in diameter or in the lower 20% of the size range in both years. In fact, the mean di ameter of coral colonies in the two years differed by less than 3 mm. The large proportion of colonies within the smallest size classes in both years indicates that there is recent recruitmen t, and based on the size-frequency distributions, the larger size cl asses appear to be stable. However, the difference in mean maximum diameter between years is primarily a re sult of lower numbers in the smallest 3 size classes (0 15 mm max diameter). This sh ift could be indicative of a difference in the strength or timing of recruitment in 2007 or a difference in mo rtality of the smallest size classes. Further monitoring of settlement, recruitment, and subsequent survival of S. radians in the SMK may help determine the relative importance of pre-se ttlement and post-settleme nt processes resulting in the observed size-frequency distribution. Additionally, population mode ls of corals suggest that increases in the frequency and/or intensity of disturbance tends to skew size-frequency distributi ons toward the right (Done 1987), and such an effect could have been operating in the SMK. For example, S. radians at this location were subject to over 20C changes in temperature and over 20 ppt changes in salinity. These ranges exceed typical conditions for more tropical populations of S. radians (e.g., Cubit et

PAGE 25

25 al. 1989). Overall, S. radians has been reported to be highly tolerant of stresses, including shading and sedimentation (Lewis 1989), and th is characteristic was confirmed by the low incidence of bleaching and other indicators of poor health among cora ls counted during the surveys. However, threshold levels of environm ental stress have yet to be determined for the SMK population of S. radians Siderastrea radians was aggregated at most sites in both years. Values of I were consistently higher than 1.00, with values r eaching the maximum possible value of 10.00 for some sites. Thus, corals were patchy at the scale of tens of meters (area sampled at each site = 25 m2). In addition, densities of S. radians varied across the 81 sites in the sampling grid, which provided evidence of patchiness at the scale of hundreds of meters. The significant variation in counts among combinations of Sites and Years was no unexpected, given the sampling design applied to a sessile, marine organi sm exhibiting an aggregated distribution at the scale of tens of meters. Regard less, results of the two surveys indicated that corals tended to occur at the same sites in both years. Patchiness can arise from several processes and their interactions. It may reflect variation in exogenous factors such as habi tat suitability and/or availability, or endogenous factors such as larval dispersal, or selective settlement and/or survival of larvae. The significant negative correlation between seagrass coverage and coral a bundance suggested that not all substrates in the sampling grid were suitable for settlement and/or survival of Siderastrea radians Qualitative observations indicated that locations with de nse seagrass typically had deeper and softer substrates than those with sparse or no seagrass. Siderastrea radians also exhibited a weak, but statistically significant, positive correlation with macroalgal coverage. This relationship probably arose because both organisms attach to a hard substr ate or survived better if they were attached

PAGE 26

26 to one. Corals typically settle on hard subs trate (Harrison & Wallace 1990), be it limestone bedrock or another coral (pers. obs.). In contrast, the pos itive correlation between coral abundance and percent cover of dr ift algae probably reflected the tendency of drift algae to become trapped on coral colonies rather than a relationship centered on suitable habitat. The relatively low correlation coefficients indicated that factors other than subs trate were influencing the distribution of coral colonies. Further res earch on substrate charac teristics (e.g., depth and composition) coupled with data on S. radians abundance could yield an improved understanding of how substrate affects the distribution of co ral colonies. Additionally, more information is needed on the dispersal of S. radians in the SMK to determine the relative importance of endogenous vs. exogenous factors in determining the observed aggrega tion patterns (see van Teeffelen & Ovaskainen 2007). The presence of conspecifics may interact w ith substrate composition to affect settlement and mortality of the early life stages of Siderastrea radians in the SMK, as Vermeij (2005) has found for S. radians populations in the Florida Keys. Planulae may use the presence of conspecifics as a cue for settlement, resulting in aggregations of corals. Optimal distance for fertilization success also may play a role in cr eating aggregated distribu tions. In fact, spatial aggregation and a female-biased sex ratio are expected in populations of brooding corals, including S. radians populations in the Caribbean (Shinkarenko 1981, Szmant 1986, Soong 1991, Ben-Yosef & Benayahu 1999). Females clustered around one or several males are thought to garner increased repr oductive success. Analyses of pa tterns in recruits, adults, and males and females will shed light on the processes th at yield aggregated distributions of colonies within the SMK (Chapter 3).

PAGE 27

27 Conclusions In summ ary, the observed distri butions of size and density of Siderastrea radians colonies within and among sites in the SMK indicate that there is recent recrui tment to the population. Large numbers of small colonies and stable num bers of larger colonies indicate that the population is stable, if not growing. Aggregatio n values coupled with a significant negative correlation between S. radians abundance and seagrass coverage highlight the pa tchy distribution of this population, which may be indicative of substrate suitability and/or availability. The addition of data on the reproductive characterist ics of this species in the SMK will further augment our understanding of its population dynamics.

PAGE 28

28 Table 2-1. Environmental conditions at four samp ling stations near the Homosassa River and the St. Martins Keys. Values based on data collected monthly from November 1996 through December 2007 (Jacoby et al. 2008). SE = standard error. Parameter Homosassa Station 1 2 3 6 Depth (m) Mean 0.790.530.82 1.37 SE 0.030.020.04 0.02 Minimum 0.20.10.2 0.8 Maximum1.81.52.6 2.2 Temperature (C) Mean 22.9023.3023.30 22.70 SE 0.500.500.50 0.50 Minimum 10.010.410.0 9.6 Maximum32.433.333.1 32.3 Salinity (ppt) Mean 24.6726.8922.49 26.19 SE 0.383.350.37 0.38 Minimum 12.014.813.0 15.9 Maximum33.535.433.2 36.4 Light Extinction Coefficient (kd; m1) Mean 0.981.031.17 1.04 (based on readings at depths 0.5 m) SE 0.060.080.06 0.04 Minimum 0.20.40.3 0.2 Maximum2.42.92.2 2.4 Secchi Depth (m) Mean 0.790.530.80 1.37 (based on replacing readings of BottomSE 0.030.020.03 0.02 with depths) Minimum 0.20.10.2 0.7 Maximum1.81.52.3 2.2 Table 2-2. Results of two-way ANOVA using log10(coral counts + 1). Factor df SS MS F p Year 1 0.248 0.248 2.100.148 Site 41 72.590 1.771 14.990.000 Year x Site 41 30.670 0.748 6.330.000 Error 754 89.053 0.118 Table 2-3. Evidence of partial co lony mortality due to bleachi ng, encrustation by algae and/or sponge, and presence of sediment for Siderastrea radians colonies in the St. Martins Keys. Partial colony mortality (no. colonies) Year Number of colonies Bleaching Encrustation Sedimentation Total % mortality 2006 1609 53 71 36 9.9% 2007 1288 22 128 27 13.7%

PAGE 29

29 Figure 2-1. St. Martins Keys, Florida, showi ng study sites for the 2006 and 2007 surveys. The distance between any two neighboring sites is 500 m. SMMAP = St. Martins Marsh Aquatic Preserve.

PAGE 30

30 Figure 2-2. Sampling stations for environmenta l data (modified from Jacoby et al. 2008).

PAGE 31

31 Height = 0.83(Diameter) r2 = 0.90, p < 0.001 0 40 80 120 160 020406080100120 Maximum diameter (mm)Height (mm) Figure 2-3. Linear regression of Siderastrea radians colony heights vs. maximum diameters.

PAGE 32

32 0 50 100 150 200 2500 5 1 0 15 2 0 2 5 30 3 5 40 4 5 5 0 55 6 0 6 5 70 7 5 80 8 5 9 0 95 1 00 1 05 11 0 1 15 12 0 125Maximum diameter (mm)Number of colonies 2006 2007 Figure 2-4. Size-frequenc y distributions of Siderastrea radians colonies in 2006 and 2007.

PAGE 33

33 0 10 20 30 40D01 D04 D05 D46 D27 D48 D28 D49 D06 D52 D30 D58 D31 D57 D32 D56 D11 D60 D12 D61 D68 D67 D35 D36 D64 D16 D70 D18 D71 D20 D77 D38 D76 D39 D74 D21 D78 D22 D79 D23 D24 D25 R1R2R3R4R5R6R7R8R9 Rows of sites from north to south and sites within rows from west to eastMean counts 95% CL (colonies 0.25 m-2) 2006 2007 Figure 2-5. Back-transformed mean counts of Siderastrea radians colonies 95% confidence limits (CL).

PAGE 34

34 Figure 2-6. Mean densities of Siderastrea radians (colonies m2) in 2006. SMMAP = St. Martins Marsh Aquatic Preserve.

PAGE 35

35 Figure 2-7. Mean densities of Siderastrea radians (colonies m2) in 2007. SMMAP = St. Martins Marsh Aquatic Preserve.

PAGE 36

36 Figure 2-8. Mean densities of Siderastrea radians (colonies m2) for 2006 and 2007. SMMAP = St. Martins Ma rsh Aquatic Preserve.

PAGE 37

37 CHAPTER 3 REPRODUCTIVE CHARACTERISTICS OF Siderastrea radians Introduction Most m arine invertebrates e xhibit complex life cycles that include a planktonic larval phase. The genetic structure and survival of popul ations, along with the species composition of assemblages are dependent on the outcome of pro cesses affecting this phase and the subsequent addition of new recruits to populations (V ermeij 2005). The settlement and subsequent recruitment of larvae are therefor e crucial life history characteris tics, and many studies of marine benthic invertebrates have, consequently, focu sed on the survival and dispersal of larvae. Notwithstanding the importance of larval dynamics, research with in the past thirty years has begun to focus on the reproductive ecology of be nthic invertebrates as a potential factor controlling population dynamics and an important component in the evolution of life histories (see Pennington 1985). The results of such investig ations should be partic ularly important for protection and restoration of corals, which are under stress worldwide, because reproductive ecology should play a role in determining the functional roles, interchangeability, and contributions to resilience for different spec ies of corals (Bellwood et al. 2004). Beyond larval dispersal, key aspects of reproductive ecology in clude sexuality, reproductive mode, seasonality and timing of reproduction, fecundity, sex ratio, a nd variations in these characteristics with variations in abundance a nd level of aggregation. In corals, there are typically four patterns of sexual reproduction, consisting of gonochoric or hermaphroditic species with broadcast spawning or brooding modes of development. The sexuality of a coral refers to whether the spec ies is gonochoric or hermaphroditic. A gonochoric species is represented by two distinct sexes, whereas a hermaphroditic species may contain both sexes either at the same time (simultaneous) or at different stages in the life history (sequential).

PAGE 38

38 Sexuality is typically conserved within a species throughout its range (Harrison & Wallace 1990). In contrast to sexuality, reproduc tive mode may vary between geographically separated populations of a given species and within local populations (Harrison & Wallace 1990). For example, populations of the reef coral Goniastrea aspera in Palau were found to brood and release planulae (Abe 1937, Motoda 1 939), but Babcock (1984) suggested that they were hermaphroditic, broadcast spawners on the Great Barrier Reef. Populations of this same coral in Okinawa have been repo rted to be both hermaphroditic, broadcast spawners and to brood planulae (Heyward et al. 1987, Hayashibara et al 1993). Therefore, one should not assume that reproductive mode would remain consistent across the entire range of a species. Sex ratios in species with separate se xes tend to approximate 1:1 (Fisher 1930, Hamilton 1967). Even hermaphrod itic species should allocate appr oximately equal resources to male and female gametes (Maynard Smith 1971). Darwin (1871) and Fi sher (1930) recognized that sex ratios evolve through frequency-dependent selection on the relative reproductive success of male and female offspring. In other words, imba lances in sex ratios ar e self-correcting because offspring of the minority sex will generally experience greater than average reproductive success, which, in turn, can lead to an increase in production of the minority sex if this trait is heritable; a balancing of the sex ratio l eads to a stable evolutionary equilibrium. Nevertheless, species do exhibit biased sex ra tios. A bias toward males, for example, has been reported for the brittle star Ophiactis savignyi (McGovern 2002) and Richardsons ground squirrels Spermophilus richardsonii (Schmutz et al. 1979). Female-biased sex ratios occur in a wide range of coral taxa including gorgonians ( Acabaria biserialis Ben-Yosef & Benayahu 1999), red corals ( Corallium rubrum Santangelo et al. 2003), and stony corals, such as Siderastrea stellata (De Barros et al. 2003).

PAGE 39

39 Biased sex ratios have been attributed to various causes, such as asexual propagation (Sammarco 1982), inbreeding or parthenogenesis (H amilton 1967), sex changes in adult colonies (Rinkevich & Loya 1987), developmental activati on of ova by sperm of other species (Stenseth & Kirkendall 1985), and environmental de termination of sex (Charnov & Bull 1977). Furthermore, if male reproductive output is cap able of greatly exceeding that of females, a female-biased sex ratio may be evolutionarily advantageous. For this reason, the presence of a skewed sex ratio in gonochoric, brooding cora ls is not unexpected (Harrison & Wallace 1990). The reproductive success of a gonochoric, broodi ng coral is related to an interaction between the spatial distribution of colonies and the sex ratio in the population (Ben-Yosef & Benayahu 1999). In populations where only the fema les brood, the number of female colonies is likely to become the factor that limits repr oductive success because sperm from a single male colony can fertilize multiple eggs, which become the planulae brooded by multiple female colonies. In this scenario, a female-biased sex ratio should evolve because colonies that produce a higher proportion of females transmit their ge nes more successfully and garner increased fitness (Maynard Smith 1978, Charnov 1982). In cont rast to brooders, broadcast spawners, such as Siderastrea siderea typically exhibit a 1: 1 sex ratio (Soong 1991). In addition to sex ratio, the presence of a uni form, random, or aggreg ated distribution of males and females is also a critical influence on reproductive success. In plants, a random distribution over relatively large spatial scales is considered optimal for pollen distribution and seed dispersal (Bawa & Opler 1977). This situati on may differ for sessile invertebrates if the threshold distance for successful fertilization becomes a limiting factor. The likelihood of successful fertilization may decreas e significantly if males and females are separated by a few

PAGE 40

40 meters, as shown in Plexaura cuna a broadcast spawning octoco ral (Coma & Lasker 1997), and other marine invertebrates (Penningt on 1985, Levitan 1991, Brazeau & Lasker 1992). However, aggregated distributions also may be the result of other influences. For example, corals depend on various environmental or chemi cal cues when timing settlement and/or larval metamorphosis. The presence of crustose cora lline algae has been shown to induce larval settlement and metamorphosis in both soft (Sla ttery et al. 1999) and ha rd corals (Heyward & Negri 1999). Furthermore, habitat characteristic s, such as water depth (Edmunds et al. 2004), sediment depth, or substrate composition (Ver meij 2005), also influence settlement and subsequent recruitment. The processes that yield a pa rticular spatial distribution of males and females may be influenced by density. Density in plants and in sects has been shown to affect secondary sexual characteristics (Lovett Doust et al. 1987) and sex ratios (Myers et al. 1998), respectively. The difference between the sex ratios of a Costa Brava population of the red coral Corallium rubrum and a population in Italy (Santangelo et al. 2003) has been hypothesi zed to be due to differences in density and larval recruitment between th e two sites (Tsounis et al. 2006). Optimal fertilization rates and, conseque ntly, sex ratios in gorgonians ar e affected by population density (Brazeau & Lasker 1990). In addi tion, the presence and/or density of adult conspecifics may influence larval settlement in many marine invertebrates. For example, adult density was shown to positively influence recruit abundance in Siderastrea radians populations in the Florida Keys (Vermeij 2005). In summary, several key questions that bear on reproductive success and, ultimately, population structure, relate to the reproductive characteristics of corals. Do colonies exhibit gonochorism or hermaphroditism acro ss the species geographic rang e? Are sex ratios balanced

PAGE 41

41 or biased between and within populations? Does density or level of aggrega tion affect sex ratios? In addition, variation in reproductive characteristics has broad im plications for how a species will respond to environmental stressors and natu ral and anthropogenic disturbances. Therefore, basic information on reproductive characteristics for a species with a co smopolitan distribution, like Siderastrea radians represents a significan t contribution to the field of coral ecology. Typically, small massive corals like Siderastrea radians exhibit life history characteristics that differ from large massive species. Massive corals with surface areas under 100 cm2 generally brood larvae, reproduce often and throu ghout the year, reach puberty at a small size, and exhibit high recruitment rates (see Soong 1993). In fact, some of these reproductive characteristics have been identi fied for specific populations of S. radians (Duerden 1904, Szmant 1986, Soong 1991, Soong & Lang 1992). Sexuality and reproductive mode appear to be known for Siderastrea radians Although an initial report detailing S. radians postlarval development suggest s that the species may be hermaphroditic (Duerden 1904),subsequent studies indicate that it is more likely to be gonochoric (Szmant 1986, Soong & Lang 1992). In addition, populations of S. radians in Panama have been shown to exhibit brooding as a reproductive mode (Soong 1991), which may increase reproductive success (Szmant 1986). Pla nulae of brooding species often settle within hours of release and near th eir point of release (Duerd en 1904, Lewis 1974, Vermeij 2005), thereby escaping the relatively high rate of mortality associated with planktonic development (Szmant 1986). In addition, brooding generally is coupled with multiple reproductive cycles per year, resulting in more opportunities for recr uitment than a single spawning cycle. Although many scleractinian coral species (especially broadcast spawners) re produce on a lunar or seasonal basis, S. radians in Panama exhibits protracted reproduction and broods year-round

PAGE 42

42 (Soong 1991). Furthermore, there was no evidence of lunar synchrony in larval development or release. However, latitudinal variation in the timing of gametogenesis has been linked to differences in water temperature due to upwelling for species such as Siderastrea stellata (De Barros et al. 2003). If geogra phically distinct populations of S. radians experience differences in sea surface temperatures, spawni ng and gametogenesis may differ from what has been observed in the Caribbean. The sex ratio of Siderastrea radians populations in both Puerto Rico and Panama was found to be skewed towards females (1:20, Szmant 1986; 24:526, Soong 1991), and populations in Bermuda also exhibit a highly female-biased sex ratio (S. de Pu tron, University of Swansea in Wales, pers. comm.). It is unlikely th at the proliferation of females in S. radians populations can be explained by asexual repr oduction based on the morphology a nd habitat of this species (Harriott 1983). Selective mortality of male planul ae and/or colonies also is unlikely to produce a skewed sex ratio given the stochastic nature of mortality an d the early age at which most mortality occurs (Hughes 1983). This study focused on the sex ratio of the reproductively active component of the population, i.e., the operational sex rati o, which represents the outcome of all processes operating earlie r in the life history. To tease out interactions among reproductive characteristics, abundance or density, and aggregation, I employed a sampling regime designed to quantify these parameters for Siderastrea radians in the St. Martins Keys, Florida (SMK). This portion of my research focused on two main goals: (1) to elucidate the key reprod uctive characteristics of sexuality, reproductive mode, sex ratio, and puberty size for the SMK population; and (2) to quantify the relationship between recruit and conspecific abundance.

PAGE 43

43 Materials and Methods Corals cannot be sexed in the field unless planula and/or sperm release is observed; therefore, the reproductive characteristics of Siderastrea radians in the SMK were determined by histological examination of tissue samples from colonies collected at study sites selected to reflect variation in density and aggrega tion as measured by Morisitas Index (I; Eq. 2-1). The histological results were combined with counts of colonies and measures of maximum diameters to elucidate key asp ects of the reproductive demogra phy, or variation in reproductive ecology, of Siderastrea radians The presence of ova, sperm, a nd/or planulae indicated maturity and sexuality. Size-frequency dist ributions of mature and non -reproductive colonies provided estimates of size at puberty. Comparisons of sex ratios among sites yielded insights into potential interactions with density and a ggregation, as did evaluation of th e relationship between recruits and conspecifics. Coral Surveys Based on the results of surveys in 2006 and 2007, 17 sites were select ed to: (1) represent different combinations of dens ity and aggregation (Table 3-1), and (2) encom pass the north, west, and southwest regions of the sampling gr id (Fig. 3-1). Between 26 and 28 June 2007, eight 50-m transects were deployed at each site from the coordinate identifying the site. Bearings started at 0 (N), were incremented by 45, a nd ended at 315 (NW). Along each transect, three 0.25-m2 quadrats were placed at distances chosen with the aid of random numbers. In each of the resulting 24 quadrats, corals we re counted and assigned to one of four size categories based on maximum diameters: (1) 0.0 4.9 mm, (2) 5.0 19.9 mm, (3) 20.0 49.9 mm, and (4) >50.0 mm. These size categories captured variation seen in size-frequency distributions generated from surveys in 2006 and 2007, as well as size catego ries deemed important in the reproductive biology of Siderastrea radians in the Caribbean (Soong & Lang 1992). For example, the first

PAGE 44

44 size category (0.0 4.9 mm) was designed to encompass imma ture corals, and the third category (20.0.9 mm) began at the puberty size of S. radians in Panama (Soong & Lang 1992). Coral counts were used to confirm variation in densit y and aggregation. These results were used to identify 10 sampling sites for coral collection. Coral Collection Siderastrea radians colonies were relatively sm all, with most being less than 100 mm in diameter; therefore, whole colonies were collecte d. Attempts to extract cores from large colonies using either a pneumatic drill or an arch punch fa iled to yield suitable samples or destroyed the colony. During collection, the basal attachment of the colonies was severed with a hammer and masonry chisel. Based on the results of counts, corals were collected from 10 sites chosen to differ in density of colonies and degr ee of aggregation between 30 Ju ly and 10 August 2007. Starting at the central coordinate, each si te was divided into 8 quadrants of 45. The area was further divided into 16 subquadrants, with 8 subquadrants running 0 50 m from the central coordinate and the remaining 8 subquadrants running 50 100 m from the central point. Using a randomized list of the first 8 subquadrants, one subquadrant wa s selected, the area was scanned for coral, and a 0.25-m2 quadrat was haphazardly placed in a lo cation that contained coral colonies. Coordinates of all quadrats were recorded with a handheld global positioning system (GPS 12 XL, Garmin) contained in a dry bag. All corals within th e quadrat were collected and placed into a Ziploc bag containing ambient seawater. This process was repeated until a minimum of three quadrats with coral were identi fied and at least 50 corals were collected. The more distant set of subquadrants was used only if these conditions were not satisfied by sampling in the 0 m subquadrants. Corals were transported to the boat and transferred from bags to jars

PAGE 45

45 filled with a 1:4 solution of Z-Fix (buffered zinc formalin, Anatech Ltd. USA) and ambient seawater, respectively. Each ja r contained one coral colony, w ith a label comprising a unique identification number, the site number, and the quadrat number. Corals were transported to the laboratory for histology. Histological Analysis Containers with corals were ag itated every 2 h for the firs t 8 h to ensure penetration of the fixative into the tissue. Samples were left in th e fixative solution for at least 48 h. Used fixative was disposed according to protocols approved by University of Florida Environmental Health and Safety Division. The calcium carbonate skeleton of the colonies needed to be removed to facilitate sectioning and allow for examination of tissues. In an effort to promote efficient and effective decalcification, a 30 mm x 40 mm portion of colonies larger than 50 mm in diameter was removed using a wet tile saw. Central polyps were chosen based on reports that infertile polyps generally were associated with margins of co lonies (Chornesky & Peters 1987). Remnants of large colonies were disposed according to Univ ersity of Florida Environmental Health and Safety protocols. All specimens were decalcified using a soluti on consisting of 2.5% hydrochloric acid and a chelating agent, ethylenediamin etetraacetic acid (EDTA), accordi ng to standard procedures (E. Peters unpubl. data). Decalcification times vari ed according to the size of the specimens. Following decalcification, one or two tissue samples (~7.5 mm x 15.0 mm) were cut from each specimen and placed in tissue cassettes under running tap water for 24 h. After rinsing, cassettes were stored in 75% ethanol until they were processed. Tissue samples were dehydrated and embedded in paraffin (Paraplast) in preparation for sectioning with a microtome. Samples were serially sectioned at a thickness of 6 m, which

PAGE 46

46 yielded approximately 60 sections per specimen Sections were floated onto five to ten precleaned slides that were rubbed with L-Lysine (Fisher Scientif ic) prior to section placement. Slides were dried overnight on a slide warmer or in an oven. Thr ee to five slides per specimen were stained using hematoxylin and eosinY (Hematoxylin 7211, Eosin-Y 7111, Richard-Allan Scientific), which is an approach commonly used to distinguish various cell and tissue components. A coverslip was added to each slid e using Permount (Fishe r Scientific). Each stained slide was examined under light micros copy for gonadal material, which was used to identify the sex of individual polyps. Sex Ratio Sex ratios were calculated from the results of histological examin ation of corals. Chisquare tests were used to compare sex ratios (c alculated as males:females) calculated across all sites to sex ratios reported for Siderastrea radians in Puerto Rico and Panama (Szmant 1986, Soong 1991). A two-way analysis of variance (ANOVA) was used to test for signifi cant variation in sex ratios among sites with differing densities and degrees of aggregation. Sex ratio was operationally defined as the number of mature ma les divided by the number of mature females. Sites were classified according to the densities and Morisitas Indices calculated from counts in the 24 quadrats comprising the June 2007 coral surv eys. The resulting classes were treated as levels of fixed factors. Before the analysis, data were tested for normality with a Ryan-Joiner test and homoscedasticity with Cochrans test Data were transformed if necessary. Puberty Size Cum ulative size-frequency distributions were prepared for non-reproductive coral colonies, females, and males using the results of histological examinatio ns. These distributions were used to define puberty size, or the averag e size at first reproducti on. Differences in mean

PAGE 47

47 maximum diameters among males, females, and non-reproductive colonies were investigated with a one-way ANOVA. Before the analysis, data were tested for normality with a Ryan-Joiner test and homoscedasticity with Cochrans te st. Data were transformed if necessary. Puberty size was calculated us ing several methods. In one calculation, colonies were ranked according to increasing size, and puberty size represented the maximum diameter of the smallest colony in the first group of 20 colonies that contained 90% or more fertile colonies (i.e., 18 or more fertile col onies; Soong & Lang 1992). In cont rast, puberty size also was calculated as (1) the colony si ze below which there was no evid ence of mature gonads (Hall & Hughes 1996), and (2) the colony size at which 50% of colonies exhibited mature gonads. Distribution of Recruits Relative to Conspecifics Relationships between recruits, which were ope rationally def ined to be solitary polyps, and conspecifics were investigated using linear regression. Numbers of recruits and conspecifics were drawn from the pooled data collected dur ing the 2006 and 2007 surveys, with counts being sums across ten, 0.25-m2 quadrats along each transect. Three relationships were examined. Number s of recruits were regressed against (1) numbers of all conspecifics, (2) numbers of mature conspecifics, which were operationally defined as colonies equal to or larger than puberty size, and (3) numbers of immature conspecifics, operationally defined as colonies smaller than puberty size. Before the analyses, data were tested for normality with a Ryan-Joiner test and homoscedasticity with Cochrans test. Data were transformed if necessary. Results Coral Surveys The m ajority of corals surveyed fell into the 20.0 49.9 mm and 5.0 19.9 mm size classes (Fig. 3-2). In addition, 41% of corals were in the two smallest size classes, 0.0.9 mm

PAGE 48

48 and 5.0.9 mm. Thus, the size frequency distribu tion was similar to earlier surveys (see Fig. 2-4). Densities at the 17 selected sites ranged from 0.0 to 36.5 colonies m2 (Fig. 3-3). The overall mean density for all sites was 9.78 colonies m2. Morisitas Indices (I) ranged from 0.00 to 24.00 across the 17 sites (Fig. 3-3). As expected for an index designed not to correlate with density, I-values at densities less than 5.0 colonies m2 varied from 2.3 to 24.0 (Fig. 3-3). Ten of the 17 sites were selected fo r coral collection (Fig. 33). These sites covered nearly the full range of densit ies and levels of aggregation. Reproductive Strategy The 598 colonies collected from the 10 sites had maximum diameters ranging from 0.2 mm to 170.7 mm, with a mean standa rd error of 26.6 0.85 mm. The size-frequency distribution (Fig. 3-4) was similar to that found in the 2006 and 2007 surveys (see Fig. 2-6), with 54% of corals being smaller than 25 mm in maximum diameter. Of the 581 colonies examined, 357 contained no identifiable sperm, eggs or planulae. All polyps examined in every mature colony were of the same sex, which provided no evidence of hermaphroditism and reasonable evidence that Siderastrea radians in the SMK are gonochoric. Planulae were not observed, so there was no evidence that the corals are brooders. Sex Ratio The colonies containing evidence of gonads comprised 108 m ales and 116 females. This sex ratio, calculated here as males:females, 0.93:1.00, does not differ significantly from 1:1 ( 2 = 0.286, p = 0.593), but it is signif icantly different from the fe male-biased sex ratios of 1:20 and 1:22 reported from Puerto Rico and Panama (Szmant 1986, 2 = 933.011, p < 0.0001; Soong 1991, 2 = 1022.278, p < 0.0001). Sex ratios, expressed as males:females, calculated

PAGE 49

49 for individual sites ranged from 0.28:1.00 to 1.33:1.00, with a mean standard error of 0.89:1.00 0.10 (Table 3-2). Across all sites, 38% of colonies exhibited reproductive activity, and values for individual sites ranged from 18% to 64% (Table 3-2). Inactiv e colonies, or those above the puberty size as defined by Soong & Lang (1992), comprised 45 of the 581 collected colonies (Table 3-2). The frequency of fertile colonies increased in larger size classes, but the frequencies were always lower than those reported by (S oong & Lang 1992) for Panamanian Siderastrea radians (Table 3-3). Based on data from 24 quadrats sampled in each site, the 10 sites were classified into high and low categories for both density of Siderastrea radians colonies and level of aggregation as measured by Morisitas Indices (Table 3-4, Fig. 35). The ratios of males to females were normal and homoscedastic. The ratio of males to fema les did not vary signifi cantly among classes of density, classes of aggregation, or a combina tion of the two (Table 3-5, Figs. 3-6 & 3-7). Puberty Size Estim ated puberty size varied according to the methods applied. Applying the methods of Soong & Lang (1992) yielded a puberty size of 39.8 mm, compared with a puberty size of 20.0 mm reported for Siderastrea radians in Panama. The smallest colony with mature gonads was 3.8 mm in diameter (method of Hall & H ughes 1996). Alternatively, 50% of colonies exhibited gonadal material at 32.8 mm maximum diameter, and this estimate of puberty size was used in further analyses (Fig. 3-8). Square-root transformed maximum diameter s were homoscedastic, but non-normal. A conservative interpretation of the results of ANOVA indicated that the mean maximum diameters of males were larger than those of females, which were larger than those of nonreproductive colonies ( F = 115.9, df = 2, 578, p < 0.001, Fig. 3-8). The back-transformed mean

PAGE 50

50 maximum diameter for non-reproductive col onies was 15.6 mm with lower and upper 95% confidence limits of 13.4 and17.8 mm. The back -transformed mean maximum diameter for female colonies was 32.6 mm with lower a nd upper 95% confidence limits of 29.5 and 39.8 mm. The back-transformed mean maximum diameter fo r male colonies was 42.2 mm with lower and upper 95% confidence limits of 38.7 and 45.9 mm. Distribution of Recruits Relative to Conspecifics Counts of solitary polyps and larger coloni es sum med over the 10 quadrats sampled in each of 81 sites during the 2006 and 2007 surveys were normal and homoscedastic following the appropriate log-transformation. A regression based on counts from quadrats with solitary polyps showed a significant positive relationship between numbers of solitary polyps and numbers of all other conspecifics (r2 = 0.27, p < 0.001, Fig. 3-9). Mature cons pecifics could be identified by applying the puberty size derive d from the maximum diameter at which 50% of colonies displayed gonads, i.e., colonies equal to or larger than 32.8 mm in maximum diameter. A regression showed a positive, but weaker, relationship between numbers of solitary polyps and mature conspecifics (r2 = 0.15, p = 0.0008, Fig. 3-10). Further, a regression between solitary polyps and conspecifics smaller than the pubert y size showed the strongest positive relationship (r2 = 0.32, p < 0.001, Fig. 3-11). Discussion Variation in reproductive characteristics ha s been described for several anthozoans (Rinkevich & Loya 1979, Benayahu & L oya 1983, Kojis 1986, Soong 1991, Fan & Dai 1995, Sakai 1997, Kram arsky-Winter & Loya 1998, Santa ngelo et al. 2003, Tsounis et al. 2006, Gori et al. 2007). For example, studies have shown in traspecific variation in reproductive mode, sex ratio (Benayahu & Loya 1983, Tsouni s et al. 2006, Gori et al. 2007) and interspersion of males and females (Kramarsky-Winter & Loya 1998) across various spatial scales in a wide variety of

PAGE 51

51 species, including sea anemones (Rossi 1975), gor gonians (Gori et al. 2007) and scleractinian corals (Rinkevich & Loya 1979). Harrison & Wallace (1990) suggested that although some facets of reproductive strategy (e.g., sexuality) may be genetically determined and consistent across a species geographic rang e, other aspects (e.g., reproductive mode, size at maturity, and reproductive season) may be influenced by loca l environmental variables. In fact, even genetically determined sexuality may exhibit variation (see Tomascik & Sander 1987). Sexuality Sexuality is generally evalua ted through histological analysis of tissue samples when organism s lack other sexually dimorphic character istics. In the present study, all specimens with gonadal material were sexually dichotomous, i. e., only eggs or sperm were found in any individual colony. This eviden ce of gonochorism is consistent with studies of Caribbean populations of Siderastrea radians (Szmant 1986, Soong 1991), and, in combination, these findings corroborate the concept that sexuality generally remains consistent within each scleractinian family throughout its ge ographic range (Harrison & Wallace 1990). Although Caribbean and SMK populations of Siderastrea radians are purported to be gonochoric, available results do not exclude the possibility of sequential hermaphroditism because the sexuality of individual colonies has not been traced through time. Thus, the possibility that S. radians is a sequential hermaphrodite remains to be explored. However, sequential hermaphroditism in sessile organisms is not common, with few corals exhibiting this reproductive strategy (Marshall & Stephenson 1933, Glynn et al. 2000, Neves & Pires 2002). In addition, skewed sex ratios characterize popul ations of these sp ecies (Szmant 1986, Soong 1991). The sex ratio of the SMK population of S. radians was not skewed and males and females were abundant across all size ranges; therefore, sequential hermaphroditism in this population is unlikely.

PAGE 52

52 Sex Ratio Geographic variation in the reproductive strategy of Siderastrea radians was exem plified by differences in sex ratios betw een populations in the SMK and th e Caribbean. The sex ratio in the SMK differed significantly from ratios re ported for Panamanian (24:526, Soong 1991) and Puerto Rican populations (1:20, Szmant 1986). The observed sex ratio in the SMK population was approximately 1:1 and the sample size was large (n = 581), so it is unlikely that the estimate was inaccurate. However, samples were only collect ed during a two-week period from 30 July to 10 August 2007, unlike the year-long sampling regimes utilized by Soong (1991) and Szmant (1986). This snapshot of the operational sex ratio of S. radians at the SMK may be affected by seasonal or cyclic maturation of gona ds. However, inaccurate sex ratios typically present as highly skewed or comprising only one sex (e.g., Duerden 1904). This is not to say that a highly skewed sex ratio is inherently inaccurate. In fact, female-biased sex ratios are common in brooding species. Szmant (1986) suggested that sexual reproducti on via brooding solely in females of gonochoric species should naturally result in a female-biased sex ratio, as seen in Siderastrea radians in Puerto Rico and Panama. Only the females brood in most coral species adopting this reproductive strategy, and the limited space available for brooding within each polyp may exert a selective pressure for an increase in the proportion of fe male colonies (Szmant 1986). However, there are reported cases of gonochoric, brooding corals wi th a 1:1 sex ratio, including Balanophyllia elegans (Fadlallah & Pearse 1982), Porites porites (Tomascik & Sander 1987), and Leptopsammia pruvoti (Goffredo et al. 2006). The population of S. radians in the SMK may belong in this group as evidenced by the absence of significant variatio n in sex ratios across two spatial scales, i.e., within and among sites.

PAGE 53

53 Sex ratios also may be affected by spatial di stributions of conspecifics. Regardless of whether sex determination occurs pre-settlement (e.g., facultative sex determination determined by temperature) or post-settlement (e.g., envi ronmental sex determination due to social interactions), one would expect a sex ratio of approximately 1:1 at low densities, because it facilitates interactions between the sexes. At hi gher densities, a single male may successfully fertilize many females, which could result in a female-biased sex ratio. Although there was no significant variation in sex ratio across sites that differed in de nsity and degree of aggregation, the spatial distribution of colonies may indi rectly affect the ob served sex ratio of Siderastrea radians Thus, future research could determine if the presence and/or sex of conspecifics act as cues for settlement of S. radians larvae and, if so, how these cues interact with density, aggregation, and distance between conspecifi cs (see Vermeij 2005) to affect sex ratios. An increase in asexual reproduction at low densit ies also may result in skewed sex ratios, as has been reported for fema le-dominated populations of Siderastrea radians Porites lutea and P. lobata (Kojis & Quinn 1981, Tomascik & Sander 1987) or even the absence of one sex, as reported by Duerden (1904) who observed only female colonies of S. radians In fact, Ayre & Miller (2006) argue that the optim al life-history strategy for br ooding corals involves some level of inbreeding or selfing (i.e., asexual reproduction). Although sexual reproduction may be the predominant strategy, asexual reproduction can serv e to augment recruitment, particularly when a population has suffered environmental stress or di sturbance (Highsmith et al. 1980). A flexible strategy may favor sexual reproduction when both sexes are in close proximity and asexual reproduction or increased inbreed ing when adult densities ar e low (Ayre & Miller 2006). Although beyond the scope of this study, fecundity has been suggested for use as a biological

PAGE 54

54 indicator of environmenta l stress (Kojis & Quinn 1984) and future studies of S. radians in the SMK could combine data on fecundity and sex ratios to detect evidence of stress. Puberty Size Colonies without gonadal m aterial were present across a broad size range. Although populations of Siderastrea radians are thought to reproduce y ear-round (Duerden 1904) and eggs, sperm, and planulae were obs erved in histological sections of S. radians in Puerto Rico almost year-round (Szmant 1986), seasonal repr oductive cycles may become more pronounced with increasing latitude (Harrison & Wallace 199 0). In addition, reproductive cycles could be staggered among colonies. In fact, this population of S. radians is, to my knowledge, near the northernmost limit of the species range in th e Gulf of Mexico, and, although highly stress tolerant, it may respond to fluctuations in te mperature and salinity. Effects of environmental stress and/or disturbance (e.g., collection) also may manifest through premature abortion of gametes or planulae (Fadlallah 1983, Brown & Howard 1985). Future research should entail sequential sampling of individual colonies across the breeding season to determine if there is seasonal variability in the production of gametes. The size-frequency distribution generated by coral collection was similar to those generated by surveys in 2006 and 2007; therefore, estimates of puberty size should be unbiased. Both sampling efforts recorded large numbers of small colonies, which is typical for scleractinian coral species (Bak & Meesters 1999). Based on S oong & Langs (1992) criteria for puberty, colonies in the SMK matu re, on average, at twice the si ze of colonies in Panama. In addition, there is also a significant difference in reproductive activity between Panamanian and SMK populations. In Panama, 96% to 100% of large colonies were fertile, whereas only 56% to 63% of large colonies were fertile in the SM K. Given the lower proportion of fertile colonies in the SMK, the 90% level of reproductive activity that Soong & Lang (1992) used to determine

PAGE 55

55 puberty size was replaced with the size at wh ich 50% of the population was observed to be reproductive. The resulting estimat e of 32.8 mm still indica ted an average onset of maturity at a larger size than in Panama. In general, brooding species tend to become reproductive at smaller sizes than broadcast spawners (Harrison & Wallace 1990); however, the minimum size at which reproduction occurs is not the same as puberty size, which is an estimate of the average size at first reproduction for a population. Kojis & Quinn (1985) su ggested that colony size dete rmines whether a coral is reproductive, whereas polyp age influences size at first reproduction and fecundity. Harvell & Grosberg (1988) suggested that the presence of a threshold size above which reproduction occurs indicates that either ex trinsic factors (e.g., food availabilit y, temperature and lunar cycle) or intrinsic factors (e.g., size) intera ct with spatial dist ribution to initiate sexual maturity. Beyond the threshold, a combination of age and extrinsic factors ma y modify actual size at first reproduction. Ultimately, the optimal size for first reproduction likely results from balancing growth, survival, and reproduction (Stearns 1976). Many long-lived clonal species delay reproduction throughout unfavorable conditions until attaining some minimum size. In addition, it is not uncommon for scleractinian corals to ex hibit intraspecific variat ion in size at sexual maturity. In Montastrea annularis puberty size varies widely within a single population (Szmant-Froelich 1985). Re latively late maturation in the SMK population of Siderastrea radians may indicate a different balance among influences. For example, S. radians in the SMK could allocate more resources to growth at sma ll sizes. However, mature males and females were found among the smallest colonies; therefore, colony size may not be the only important influence. Future research could examine the onset of reproduction as affected by extrinsic factors, such as density and resource availability.

PAGE 56

56 Reproductive Mode Reproductive m ode refers to how a species breeds, and scleractinia n corals utilize two primary modes. Most species spawn gametes that are fertilized externally, and they are classified as broadcast spawners. A smaller proportion of species brood planula larvae internally and subsequently release them, and these species are classified as brooders. Broadcast spawners are thought to disperse larvae across great distances, whereas broode rs are considered to be poor dispersers (Harriott 1992). However, larvae of some brooding species may exhibit protracted planktonic existences (Szmant 1986), such as Pocillopora damicornis planulae that can remain in the plankton for up to two months (Szman t & Gassman 1991). Consequently, a brooding reproductive strategy does not prec lude long-distance dispersal. Therefore, reproductive mode can combine with hydrology and other abiotic factor s to have an important effect on gene flow and population structure (Ayr e et al. 1997, Ayre & Hughes 2000, Nishikawa & Sakai 2005). Although reproductive mode is ge nerally conserved within a given species, intraspecific variation does exist (Ric hmond & Hunter 1990, Ward 1992). Geographic variation in reproductive mode does occur in species with wide latitudinal ranges. For example, Acropora humilis broadcast spawns in the Great Barrier Reef and the Red Sea, but it broods planulae at Enewetak in the Marshall Islands (Richmond 1987a, b, Ward 1992). Variation in reproductive mode also has been linked to habitat; with brooders typically occupying shallow water where disturbance is relatively high and broadcast spawners residing in calmer, deeper waters (Stimson 1978, Ward 1992). The reproductive mode of a species is difficult to determine when the reproductive cycle is not known. In fact, inaccurate c onclusions regarding reproductiv e mode and/or sex ratio can result from small sample sizes or missed reprodu ctive cycles (Harrison & Wallace 1990). Corals do exhibit reproductive cycles, especially at hi gh latitudes where breedi ng seasons and spawning

PAGE 57

57 periods tend to be shorter than in tropical regions (Harrison & Wallace 1990). In fact, Duerden (1904) observed larval release in Siderastrea radians in Kingston Harbor, Jamaica, in late June and during July (n = 5), but S. radians was shown to release planulae year-round in Panama (Soong 1991). Additionally, the laboratory spawning period of S. radians in Bermuda is seasonal, with planulae release occurring in July, August, and September (S. de Putron, University of Swansea in Wales, pers. comm.). Collection of large numbers of specimens (n = 623) over a year-long period should have accurately characterized brooding as the reproductive mode of Siderastrea radians in Panama (Soong 1991). The present study utilized a large samp le size (n = 581); however, samples were collected over a two-week period from 30 July to 10 August 2007. Thus, the lack of planulae could have reflected seasonality in reproductive timing; however, based on laboratory reports of Bermudian S. radians releasing planulae in July, August, and September (S. de Putron, University of Swansea in Wales, pers. comm.), one might expect to see planulae in histological sections of S. radians collected in July and August at the SMK, a lower latitude population. Absence of planulae also may result from either a response to stressful conditions that caused release or premature abortion of planul ae (Fadlallah 1983, Brown & Howard 1985), or geographic variation in reproductive mode. Intr aspecific variation in reproductive timing and mode among allopatric populations may be a reflection of either pl asticity or local adaptation to environmental conditions and stimuli (Richm ond & Hunter 1990). Future research could investigate seasonality in reproduction for S. radians in the SMK, and such research could incorporate experimental manipulation of exposure to environmen tal conditions to distinguish between plasticity and local adaptation.

PAGE 58

58 Distribution of Recruits Relative to Conspecifics In populations of sessile m arine invertebrates, analyses of the spatial distributions of males, females, and recruits ac ross variations in density and a ggregation provide insights into reproductive strategies and even sex determination. Spatial distri butions yield insights because settlement and recruitment have significant eff ects on reproductive success in sessile organisms that reproduce sexually. Settlement refers to the point at which larvae attach themselves to the substrate, and recruitment is the stage at which newly sett led polyps become visible (Keough & Downes 1982, Connell 1985). Logistics precluded direct observations of settleme nt and subsequent recruitment of Siderastrea radians in the SMK. However, several lines of evidence suggested that solitary polyps, with maximum diameters of 0.1.8 mm, serv ed as a reliable proxy for new recruits. Harrison & Wallace (1990) suggest that recently settled coral polyps ar e typically smaller than 2 mm in diameter; not much larger than the planulae from wh ich they developed. Duerden (1904) described th e pear-shaped planulae of S. radians as being 2 mm in length, and Soong (1991) reported a maximum le ngth of 0.8 mm for planulae. In fact, most corals recruit approximately 8 to 10 months after settlement, and individuals rarely reach diameters of 10 mm after one year of growth (Harrison & Wallace 1990). Populations of many marine or ganisms have been considered demographically open, i.e., local recruitment is not dependent on local repr oduction, with planktonic larvae recruiting from distant sources (Caley et al. 1996) Previous reports suggest that Siderastrea radians larvae are brooded internally and then rel eased into the water column (Duerden 1904), but the mere presence of planktonic larvae does not im ply an open population, as evidenced by many philopatric coral species. Philopatr ic larvae, although capable of pl anktonic dispersal, settle next to or close to parent colonies. Although larvae of S. radians are typically not thought to crawl

PAGE 59

59 directly to the substr ate and settle (but see Vermeij 2005) the duration of their free-swimming and competency periods have been demonstrated in the laboratory to be on the order of hours to days (Duerden 1904). Therefore, it is likely that larval supply to the SMK population is predominately local. In fact, the majority of re cruitment by corals on the Great Barrier Reef has been shown to be local, especially for brooding corals (Ayre & Hughes 2000). Thus, the distribution of recruits within the SMK population can provide in sights into local processes. Results from the present study confirmed that at a scale of tens of meters, recruits of Siderastrea radians occur in higher abundances where c onspecifics are more abundant. Such a result was not unexpected given the aggregated nature of this populatio n and reports that the species reproduces via brooding (Szmant 1986, S oong 1991). The significant linear regression between recruits and conspecifics was suggestive of localized dispersal, with larvae settling close to their natal colonies. In fact, Goreau et al. (1981) showed that larv ae of the brooding coral, Porites porites displayed non-random, aggregated settling behavior in the laboratory, and other studies have provided evidence for a direct rela tionship between juvenile abundance and adult cover (Bak & Engel 1979, Rylaarsdam 1983). Howeve r, at least three hypotheses could explain the spatial distribution of recr uits in the SMK population of S. radians : (1) larvae are stimulated to attach to or settle near cons pecifics; (2) settlement is random, but survival is increased through attachment to or settlement near conspecifics ; or (3) larvae settle in response to physical characteristics of the environment, which makes settlement near conspecifics more likely (Connell 1973). These hypotheses are not mutually ex clusive; it is likely that a combination of these and other factors, such as larval source and transport, resulted in th e distribution of recruits and conspecifics seen in this study.

PAGE 60

60 Although all three relationships between recrui ts and conspecifics were statistically significant, the relationship between recruits and potential parents, i.e., conspecifics equal to or larger than the estimated 32.8 mm puberty size, was weak. Furt her, the relationship between recruits and immature colonies was strongest This finding corroborates the finding that the presence of mature colonies was not a strong indicator of recruit abundance, and it further supports the need to investigate hypotheses re lated to other influences. Additionally, these relationships indicate that larval input to a site may be unrelat ed to the reproductive output of the resident adults. In other words, larvae may di sperse beyond the site where they were released. There are two seemingly competing views on di spersal and competency periods of brooded larvae. The first postulates that brooded larvae are able to settle more quickly than larvae from broadcast spawners. The second suggests that be cause of their large energy reserves, including high lipid content (Richmond 1981) brooded larvae may have competency periods that are longer than larvae of broadcast spawners (Ric hmond 1988). However, the prevailing view seems to be that larvae of brooding cora ls exhibit relatively short compet ency periods, with settlement occurring relatively quickly a nd close to the natal colony. Du erden (1904) reported laboratory competency periods of a few hours to days for Siderastrea radians However, a recent study of S. radians in Brazil (Neves et al. 2008) suggested that laborat ory experiments underestimate actual competency periods and the effective disp ersal distance generate d by local oceanographic conditions. Protracted competency periods and increased dispersa l may contribute to creating the 1:1 sex ratio observed for S. radians in the SMK by making its reproductive strategy more similar to broadcast spawning. Ultimately, an understanding of potential disp ersal distance and the effects of various influences on actual dispersal will be important in assessing the resilience of reef ecosystems or

PAGE 61

61 coral communities subject to disturbances, such as bleaching (Magalon et al. 2005). Therefore, further study of dispersal in conjunction with da ta on spatial patterns in abundance, aggregation, and reproductive strategies should improve the way corals resources are managed. Conclusions In summ ary, the gonochoric nature of Siderastrea radians in the Caribbean is conserved in the SMK population. However, a brooding reproduc tive mode cannot be confirmed. The lack of planulae in histological secti ons, coupled with the observed 1:1 sex ratio, is inconsistent with typical reproductive patterns of brooding coral species. However, this could be attr ibuted to the short collection period, a nd may reflect seasonality in reproductive timing as is exhibited by many coral species at higher latitudes. Nonetheles s, the 1:1 sex ratio and larger size at puberty of S. radians in the SMK highlight the geographic vari ation in reproductive characteristics among observed populations. The observed relationships between recrui t and conspecific abundance suggest that although colonies were aggregate d, the distribution of recruits was not tightly related to the distribution of reproductively mature colonies. This points to the importance of other factors affecting settlement and establishment of larv ae, such as dispersal distance and substrate availability and/or quality. Ag ain, these results call into question the prevalence of a brooding reproductive mode for Siderastrea radians in the SMK. Ultimately, this study demonstrates that Siderastrea radians exhibits a wide degree of geographic variation in reproductive characteristics. Such variation may have implications for a populations response to stress, climate change, and other perturbations. This variation is important to factor into management and conservation of coral resources.

PAGE 62

62 Table 3-1. Densities and Moris itas Indices based on pooled da ta from 2006 and 2007 for sites selected for coral su rveys in June 2007. Values for 2006 and 2007 combined Site Density (colonies m 2) Morisitas Index (I) D24 0.6 20.00 D18 1.0 12.00 D48 1.2 13.33 D71 1.6 9.29 D74 3.6 10.59 D28 3.8 9.71 D16 6.4 5.08 D52 8.4 4.53 D32 10.4 6.38 D31 11.6 2.66 D23 11.8 3.20 D49 12.6 5.46 D68 18.0 3.66 D67 18.0 3.88 D11 22.8 2.29 D60 63.0 1.32 D39 79.6 1.48 Table 3-2. Reproductive characteristics of Siderastrea radians colonies at the 10 coral collection sites. Immature colonies ar e classified as those less th an the puberty size of 39.8 mm maximum diameter (sensu Soong & Lang 1992); inactive colonies are those larger than or equal to puberty size that did not contain gonads in hi stological sections. Percent reproductive = percentage of all collected colonies at each site that contained gonads in histological sections. Number of colonies Site Total Males Females Immature (<39.8 mm) Inactive ( 39.8 mm) Percent reproductive Sex ratio M:M D11 55 15 13 25 2 51 1.15 D18 64 9 11 27 17 31 0.82 D23 51 2 7 32 10 18 0.28 D24 51 6 8 32 5 27 0.75 D39 86 10 14 58 4 28 0.71 D48 49 14 12 22 1 53 1.17 D49 64 9 12 43 0 32 0.75 D52 55 20 15 20 0 64 1.33 D67 54 8 12 33 1 37 0.67 D68 52 15 12 20 5 52 1.25 All sites 581 108 116 346 45 38 0.93

PAGE 63

63 Table 3-3. Frequency of fertile Siderastrea radians colonies by size class. Maximum diameter (mm) Source 0 4 4 15 15 60 60 250 This study Percent fertile 3 7 56 63 Number of colonies 38 176 321 46 Soong & Lang (1992) Percent fertile 50 86 97 100 Number of colonies 64 206 208 23 Table 3-4. Densities, Morisitas Indices (I), and density and aggregat ion classes (H: high; L: low) based on surveys of Siderastrea radians colonies in 24 quadrats at each of 10 sites. Mean Class Site Density I Density I D49 64.0 10.00 H H D67 55.0 10.00 H H D39 114.7 1.08 H L D11 55.0 4.78 H L D24 40.8 10.00 L H D18 36.6 6.00 L H D48 28.0 6.67 L H D68 52.0 1.99 L L D23 51.0 2.58 L L D52 44.0 2.26 L L Table 3-5. Results of 2-way ANOVA using ratios of numbers of males to numbers of females. Factor df SS MS F p Density 1 0.03050.03050.210.664 Morisitas Index 1 0.04390.04390.300.604 Density x Morisitas Index 1 0.01970.01970.130.727 Error 6 0.87810.1463

PAGE 64

64 Figure 3-1. Mean densities of Siderastrea radians (colonies m2) from surveys in June 2007. Data were used to determine sites for coral collections. SMMAP = St. Martins Marsh Aquatic Preserve.

PAGE 65

65 Figure 3-2. Size-freque ncy distribution for Siderastrea radians colonies sampled in June 2007.

PAGE 66

66 0 5 10 15 20 25 30 0510152025303540 Density (colonies m-2)Morisita's IndexD39 D67 D28, D32, D71 D68 D23 D31 D16 D74 D49 D48 D52 D11 D18 D24 D60Sites selected for collection of corals Sites not selected for collection of corals Figure 3-3. Mean densities of Siderastrea radians and Morisitas Indices from coral surveys in June 2007.

PAGE 67

67 Figure 3-4. Size-freque ncy distribution of Siderastrea radians colonies collected for histology.

PAGE 68

68 0 2 4 6 8 10 12 0 50 100 150 Density (colonies m-2)Morisita's Index Hi density & Hi MI Hi density & Lo MI Lo density & Hi MI Lo density & Lo MI Figure 3-5. Classes of density and aggregation (based on Morisitas Indices) for July August 2007 coral collection sites. MI = Morisitas Index.

PAGE 69

69 0% 25% 50% 75% 100% High densityHigh densityL ow densityLow density High MILow MIHigh MILow MI Percent of mature colonies Females Males Figure 3-6. Percent of mature male and female Siderastrea radians colonies across differing densities and degrees of aggrega tion. MI = Morisitas Index.

PAGE 70

70 0.0 0.5 1.0 1.5 High densityHigh densityLow densityLow density High MILow MIHigh MILow MI Sex ratio (males:females) SE Figure 3-7. Mean ratios of male to female Siderastrea radians standard errors (SE) as measured across differing densities and degrees of aggregation. MI = Morisitas Index.

PAGE 71

71 0% 25% 50% 75% 100% 0 50 100 150 200 Maximum diameter (mm)Cumulative percent of colonies Non-reproductive Female Male Figure 3-8. Cumulative frequenc y distributions for non-reproductive, female, and male Siderastrea radians colonies vs. maximum diameters.

PAGE 72

72 Log(SP + 1) = 0.29[Log(non-SP + 1)] + 0.26 r2 = 0.27, p < 0.001 0.0 0.5 1.0 1.5 0.00.51.01.52.02.5 Log(non-SP + 1)Log(SP + 1) Figure 3-9. Linear regr ession of numbers of Siderastrea radians recruits (solitary polyps) vs. total numbers of all other conspecifics. Data were log(sum + 1) transformed. SP = solitary polyps, non-SP = colonies with more than one polyp.

PAGE 73

73 Log(SP + 1) = 0.20[Log(non-SP 32.8 mm or larger + 1)] + 0.50 r2 = 0.15, p = 0.008 0.0 0.5 1.0 1.5 0.00.51.01.52.02.5 Log(non-SP 32.8 mm or larger + 1)Log(SP + 1) Figure 3-10. Linear regr ession of numbers of Siderastrea radians recruits (solitary polyps) vs. numbers of conspecifics 32.8 mm in maximum diamet er (mature colonies). Data were log(sum + 1) transformed. SP = solitary polyps, non-SP = colonies with more than one polyp.

PAGE 74

74 Log(SP + 1) = 0.33[Log( non-SP smaller than 32.8 mm + 1)] + 0.25 r2 = 0.32, p < 0.001 0.0 0.5 1.0 1.5 0.00.51.01.52.02.5 Log(non-SP smaller t han 32.8 mm + 1)Log(SP + 1) Figure 3-11. Linear regr ession of numbers of Siderastrea radians recruits (solitary polyps) vs. numbers of conspecifics < 32.8 mm in maximu m diameter (immature colonies). Data were log(sum + 1) transformed. SP = solita ry polyps, non-SP = colonies with more than one polyp.

PAGE 75

75 CHAPTER 4 GENERAL CONCLUSIONS Given the relative stability in m ean density and level of aggregation documented by all sampling in this study, results detailing reproductive characteristics in sites can be scaled to the 16-km2 grid and probably to the St. Martins Keys and nearby regions. However, care should be taken when applying information across populations because intraspecific variation may exist. For example, Siderastrea radians populations are gonochoric in Panama and the St. Martins Keys, but there is signif icant variation in sex ratio between th ese two locations. In fact, variation in reproductive characteristics is found across a wide range of cora l species, and it is exemplified by geographic and environmental variation in se x ratio, spawning cycles, and even reproductive mode. Such intraspecific variation in reproductive characteristics ma y reflect plasticity or local adaptations to environmental cond itions, or they may be attribut ed to taxonomic problems or errors in interpreting data (Harrison & Wallace 1990). Overall, we must take care when extrapolating the re sults of any study. Improved understanding of reproductive strategies and population dynamics of Siderastrea radians and other coral species has obvious imp lications for coral reef restoration and rehabilitation, especially when environmental disturbances and pe rturbations continue to degrade coral communities worldwide. Environmental st ress may affect a species reproductive strategy as manifest by intraspecific variation in sexuality and sex ratio across a species range. In addition, reproductive strategies are intimately tied to larval di spersal and recruitment dynamics, and thus, source vs. sink dynamics, which affect recovery rates after disturbances. Thus, future research on S. radians in the St. Martins Keys should include long-term monitoring of recruitment, growth, and mortalit y coupled with collection of da ta on sediment characteristics,

PAGE 76

76 dissolved oxygen concentrations, salinities, temperatures, nutri ent concentrations and other potential stressors. Lastly, this research is th e first quantitative study of Siderastrea radians in the St. Martins Keys, and it is one of the few st udies that focuses on this specie s of coral (but see Duerden 1904, Soong & Lang 1992, Vermeij 2005). The study provides information on the reproductive characteristics of a globally abundant species from an unstudied area, thus it enables broader comparisons. Despite these insights, further inve stigations into factor s affecting geographic variation in reproductive characteri stics are needed and warranted.

PAGE 77

77 LIST OF REFERENCES Abe N (1937) Postlarval developm ent of the coral Fungia actiniformis var palawensis Doderlein. Palau Trop Stn Stud 1:73 93 Ayre DJ, Hughes TP (2000) Genotyp ic diversity and gene flow in brooding and spawning corals along the Great Barrier Reef Australia. Evolution 54:1590 1605 Ayre DJ, Hughes TP, Standish RS (1997) Geneti c differentiation, reproductive mode, and gene flow in the brooding coral Pocillopora damicornis along the Great Barrier Reef, Australia. Mar Ecol Prog Ser 159:175 187 Ayre DJ, Miller K (2006) Random mating in the brooding coral Acropora palifera. Mar Ecol Prog Ser 307:155 160 Babcock RC (1984) Reproduction and distribution of two species of Goniastrea (Scleractinia) from the Great Barrier Reef province. Coral Reefs 2:187 195 Bak RPM, Engel MS (1979) Distribution, abundance and survival of juvenile hermatypic corals (Scleractinia) and the im portance of life-history strategies in the parent coral community. Mar Biol 54:341 352 Bak RPM, Meesters EH (1998) Coral population structure: the hidden information of colony size-frequency distributions Mar Ecol Prog Ser 162:301 306 Bak RPM, Meesters EH (1999) Population structur e as a response of cora l communities to global change. Am Zool 39:56 65 Bawa KS, Opler PA (1977) Spatial relationships between staminate and pistillate plants of dioecious tropical forest trees. Evolution 31:64 68 Bellwood DR, Hughes TP, Folke C, Nystrom M (2004) Confronting the coral reef crisis. Nature 429:827 833 Ben-Yosef DZ, Benayahu Y (1999) The gorgonian coral Acabaria biserialis : life history of a successful colonizer of artific ial substrata. Mar Biol 135:473 481 Benayahu Y, Loya Y (1983) Surface br ooding in the Red Sea soft coral Parerythropodium fulvum fulvum (Forskal, 1775). Biol Bull 165:353 369 Brazeau DA, Lasker HR (1990) Sexual reproduction and external brooding by the Caribbean gorgonian Briareum asbestinum Mar Biol 104:465 474 Brazeau DA, Lasker HR (1992) Reproductive success in the Caribbean octocoral Briareum asbestinum Mar Biol 114:157 163

PAGE 78

78 Brown BE, Howard LS (1985) A ssessing the effects of stress on reef corals. Adv Mar Biol 22:1 63 Caley MJ, Carr MH, Hixon MA, Hughes TP, Jones GP Menge BA (1996) Recruitment and the local dynamics of open marine populations. Annu Rev Ecol Syst 27:477 500 Charnov EL (1982) The theory of sex allocation. Princeton University Press, Princeton, NJ Charnov EL, Bull J (1977) When is sex environmentally determined? Nature 266:829 830 Chornesky EA, Peters EC (1987) Sexual reproduction and colony growth in the scleractinian coral Porites astreoides Biol Bull 172:161 177 Coma R, Lasker HR (1997) Small-scale heterogeneity of fertilization success in a broadcast spawning octocoral. J Ex p Mar Biol Ecol 214:107 120 Connell JH (1973) Population ecol ogy of reef-building corals. In: Jones OA, Endean R (eds) Biology and geology of coral reefs. A cademic Press, New York, NY, p 205 245 Connell JH (1985) The consequences of variation in initial se ttlement vs. post-settlement mortality in rocky intertidal comm unities. J Exp Mar Biol Ecol 93:11 45 Cubit JD, Caffey HM, Thompson RC, Windsor DM (1989) Meteorology and hydrography of a shoaling reef flat on the Caribbean coast of Panama. Coral Reefs 8:59 66 Darwin, C (1871) The descent of man, and select ion in relation to sex. Appleton and Company, New York, NY, 223 pp. De Barros MML, Pires DD, Castro CBE (2003) Se xual reproduction of th e Brazilian reef coral Siderastrea stellata Verrill 1868 (Anthozoa, Scleract inia). Bull Mar Sci 73:713 724 Done TJ (1987) Simulation of the effects of Acanthaster planci on the population structure of massive corals in the genus Porites : Evidence of population resilience? Coral Reefs 6:75 90 Duerden JE (1904) The coral Siderastrea radians and its postlarval development. Carnegie Institution, Washington, DC Edmunds PJ (2004) Juvenile coral population dyn amics track rising seawater temperature on a Caribbean reef. Mar Ecol Prog Ser 269:111 119 Edmunds PJ (2005) The effect of sub-lethal increases in temperature on the growth and population trajectories of three scleractinian corals on the southern Great Barrier Reef. Oecologia 146:350 364 Edmunds PJ, Bruno JF, Carlon DB (2004) Effects of depth and microhabitat on growth and survivorship of juvenile corals in th e Florida Keys. Mar Ecol Prog Ser 278:115 124

PAGE 79

79 Fadlallah YH (1983) Sexual reproduction, developm ent and larval biology in scleractinian corals: a review. Coral Reefs 2:129 150 Fadlallah YH, Pearse JS (1982) Sexual reproduction in solitary corals: synchronous gametogenesis and broadcast spawning in Paracyathus stearnsii Mar Biol 71:233 239 Fan TY, Dai CF (1995) Reproductive ecology of the scleractinian coral Echinopora lamellosa in northern and southern Taiwan. Mar Biol 123:565 572 Fisher RA (1930) Sexual reproduc tion and sexual selection In: Fisher RA (ed) The genetical theory of natural selection. Oxford University Press, Oxford, p 121 145 Glancy TP, Frazer TK, Cichra CE, Lindberg WJ (2003) Comparative patterns of occupancy by decapod crustaceans in seagrass, oyster, and ma rsh-edge habitats in a northeast Gulf of Mexico estuary. Estuaries 26:1291 1301 Glynn PW, Colley SB, Ting JH, Mate JL, Guzman HM (2000) Reef coral reproduction in the eastern Pacific: Costa Rica, Panama and Ga lapagos Islands (Ecuador). IV. Agariciidae, recruitment and recovery of Pavona varians and Pavona sp.a. Mar Biol 136:785 805 Goffredo S, Airi V, Radetic J, Zaccanti F (2006) Sexual reproduction of the solitary sunset cup coral Leptopsammia pruvoti (Scleractinia, Dendrophylliidae ) in the Mediterranean. 2. Quantitative aspects of the annual re productive cycle. Mar Biol 148:923 931 Goreau NI, Goreau TJ, Hayes RL (1981) Settlin g, survivorship and spatial aggregation in planulae and juveniles of the coral Porites porites (Pallas). Bull Mar Sci 31:424 435 Gori A, Linares C, Rossi S, Coma R, Gili JM (2 007) Spatial variability in reproductive cycle of the gorgonians Paramuricea clavata and Eunicella singularis (Anthozoa, Octocorallia) in the western Mediterranea n Sea. Mar Biol 151:1571 1584 Hall VR, Hughes TP (1996) Reproduc tive strategies of modular organisms: comparative studies of reef-building corals. Ecology 77:950 963 Hamilton WD (1967) Extraordinar y sex ratios. Science 156:477 488 Harriott VJ (1983) Reproductive eco logy of four scleractinian sp ecies at Lizard Island, Great Barrier Reef. Coral Reefs 2:9 18 Harriott VJ (1992) Recruitment patte rns of scleractinian corals in an isolated subtropical reef system. Coral Reefs 11:215 219 Harrison PL, Wallace CC (1990) Re production, dispersal and recruitment of scleractinian corals. Ecosystems of the world. 25: Coral reefs. Elsevier, Amsterdam, p 133 207 Harvell CD, Grosberg RK (1988) The tim ing of sexual maturity in clonal animals. Ecology 69:1855 1864

PAGE 80

80 Hayashibara T, Shimoike K, Kimura T, Hosaka S, Heyward A, Harrison P, Kudo K, Omori M (1993) Patterns of coral spaw ning at Akajima Island, Okinawa, Japan. Mar Ecol Prog Ser 101:253 262 Heyward A, Yamazato K, Yeemin T, Misaki M (1987) Sexual reproduction of corals in Okinawa. Galaxea 6:331 343 Heyward AJ, Negri AP (1999) Natural inducers for coral larval metamorphosis. Coral Reefs 18:273 279 Highsmith RC, Riggs AC, Dantonio CM (1980) Surv ival of hurricane-generated coral fragments and a disturbance model of reef calci fication growth rates. Oecologia 46:322 329 Hughes RN (1983) Evolutiona ry ecology of colonial reef organism s, with particular reference to corals. Biol J Linn Soc 20:39 58 Hughes TP (1984) Population dynamics based on individual size rather than age: a general model with a reef cora l example. Am Nat 123:778 795 Hughes TP, Ayre D, Connell JH (1992) The evolutionary ecology of corals. Trends Ecol Evol 7:292 295 Jacoby CA, Frazer TK, Saindon DD, Keller SR, Behringer DC Jr (2008) Water quality characteristics of the nearshore Gulf coast waters adjacent to Citrus, Hernando and Levy Counties: Project COAST 1997. Annual Report. Southwest Florida Water Management District, Brooksville, FL, 62 p Karlson RH, Hughes TP, Karlson SR (1996) De nsity-dependent dynamics of soft coral aggregations: the significance of cl onal growth and form. Ecology 77:1592 1599 Keough MJ, Downes BJ (1982) Recruitment of marine invertebrates: the ro le of active larval choices and early mortality. Oecologia 54:348 352 Kojis BL (1986) Sexual reproduction in Acropora ( Isopora ) species (Coelenterata: Scleractinia). I. A. cuneata and A. palifera on Heron Island reef, Great Barrier Reef. Mar Biol 91:291 309 Kojis BL, Quinn NJ (1981) Aspects of sexua l reproduction and larval development in the shallow-water hermatypic coral Goniastrea australensis (Edwards and Haime, 1857). Bull Mar Sci 31:558 573 Kojis BL, Quinn NJ (1984) Seasonal a nd depth variation in fecundity of Acropora palifera at two reefs in Papua New Guinea. Coral Reefs 3:165 172 Kojis BL, Quinn NJ (1985) Puberty in Goniastrea favulus : Age or size limited? Proc 5th Intl Coral Reefs Congr 4:289 293

PAGE 81

81 Kramarsky-Winter E, Loya Y (1998) Reproductive strategies of two fung iid corals from the northern Red Sea: Environmental cons traints? Mar Ecol Prog Ser 174:175 182 LaJeunesse TC (2002) Diversity and community st ructure of symbiotic dinoflagellates from Caribbean coral reefs. Mar Biol 141:387 400 Lasker HR, Coffroth MA (1999) Responses of cl onal reef taxa to envi ronmental change. Am Zool 39:92 103 Levitan DR (1991) Influence of body size and p opulation density on fert ilization success and reproductive output in a free-spawni ng invertebrate. Biol Bull 181:261 268 Lewis JB (1974) Settlement behavior of planulae larvae of hermatypic coral Favia fragum (Esper). J Exp Mar Biol Ecol 15:165 172 Lewis JB (1989) Spherical grow th in the Caribbean coral Siderastrea radians (Pallas) and its survival in disturbed habitats. Coral Reefs 7:161 167 Lirman D, Manzello D, Macia S (2002) Back from the dead : the resilience of Siderastrea radians to severe stress. Coral Reefs 21:291 292 Lirman D, Orlando B, Macia S, Manzello D, Kaufman L, Biber P, Jones T (2003) Coral communities of Biscayne Bay, Florida and adj acent offshore areas: diversity, abundance, distribution, and environmental correlates. Aquat Conserv 13:121 135 Lovett Doust J, Obrien G, Lovett Doust L (1987) Effect of density on secondary sex characteristics and sex ratio in Silene alba (Caryophyllaceae). Am J Bot 74:40 46 Magalon H, Adjeroud M, Veuille M (2005) Patterns of genetic va riation do not correlate with geographical distance in the reef-building coral Pocillopora meandrina in the South Pacific. Mol Ecol 14:1861 1868 Marshall SM, Stephenson TA (1933) The breeding of reef animals. Part I. The corals. Great Barrier Reef Expedition, 1928 29. British Museum of Natural History, London, p 219 245 Maynard Smith J (1971) The origin and maintenance of sex. In: Williams GC (ed) Group selection. Aldine Atherton, Chicago, IL, p 163 175 Maynard Smith J (1978) The evolution of sex. Cambridge University Press, Cambridge McGovern TM (2002) Sex-ratio bias and cl onal reproduction in the brittle star Ophiactis savignyi Evolution 56:511 517 Meesters EH, Hilterman M, Kardinaal E, Keetman M, De Vries M, Bak RPM (2001) Colony size-frequency distributions of scleractinian coral populations : spatial and interspecific variation. Mar Ecol Prog Ser 209:43 54

PAGE 82

82 Miller MW, Weil E, Szmant AM (2000) Coral recr uitment and juvenile mortality as structuring factors for reef benthic communities in Bi scayne National Park, USA. Coral Reefs 19:115 123 Moses CS, Swart PK, Helmle KP, Dodge RE, Merino SE (2003) Pavements of Siderastrea radians on Cape Verde reefs. Coral Reefs 22:506 Motoda S (1939) Observation of pe riod of emergence of planulae of Goniastrea aspera Verrill. Kagaku Nanyo 1:113 115 Myers JH, Boettner G, Elkinton J (1998) Maternal effects in gypsy moth: only sex ratio varies with population density. Ecology 79:305 314 Neves EG, Andrade SCS, Da Silveira FL, Solf erini VN (2008) Genetic variation and population structuring in two brooding coral species ( Siderastrea stellata and Siderastrea radians ) from Brazil. Genetica 132:243 254 Neves EG, Pires DO (2002) Sexual reproduction of Brazilian coral Mussismilia hispida (Verrill, 1902). Coral Reefs 21:161 168 Nishikawa A, Sakai K (2005) Genetic c onnectivity of the scleractinian coral Goniastrea aspera around the Okinawa Islands. Coral Reefs 24:318 323 Pennington JT (1985) The ecology of fertilization of echinoid eggs: the consequences of sperm dilution, adult aggregation, and synchronous spawning. Biological Bulletin 169:417 430 Richmond RH (1981) Ecological consid erations in the dispersal of Pocillopora damicornis (Linnaeus) planulae. Proc 4th Intl Coral Reef Symp, Manila 2:153 156 Richmond RH (1987a) Energetic relationships an d biogeographical differences among fecundity, growth and reproduction in the reef coral Pocillopora damicornis Bull Mar Sci 41:594 604 Richmond RH (1987b) Energetics, competence, and long-distance dispersal of planula larvae of the coral Pocillopora damicornis Mar Biol 93:527 533 Richmond RH (1988) Competency and dispersal of spawned versus brooded coral planula larvae. Am Zool 28:A113 Richmond RH (1997) Reproduction and recruitment in corals: critical links in the persistence of reefs. In: Birkeland C (ed) Life and death of coral reefs. Chapman & Hall, New York, NY, p 175 197 Richmond RH, Hunter CL (1990) Reproduction and recruitment of corals: comparisons among the Caribbean, the Tropical Pacific, a nd the Red Sea. Mar Ecol Prog Ser 60:185 203

PAGE 83

83 Rinkevich B, Loya Y (1979) Repr oduction of the Red Sea coral Stylophora pistillata II. Synchronization in breeding and seasonality of planulae shedding. Mar Ecol Prog Ser 1:145 152 Rinkevich B, Loya Y (1987) Variability in th e pattern of sexual reproduction of the coral Stylophora pistillata at Eilat, Red Sea: a l ong-term study. Biol Bull 173:335 344 Rossi L (1975) Sexual roles in Cereus pedunculatus (Boad.). Pubbl Staz Zool Napoli 39(Suppl.):462 470 Rowan R, Knowlton N (1995) Intraspecific di versity and ecological zonation in coral algal symbiosis. Proc Natl Acad Sci USA 92:2850 2853 Rylaarsdam KW (1983) Life histories and abundan ce patterns of colonial corals on Jamaican reefs. Mar Ecol Prog Ser 13:249 260 Sakai K (1997) Gametogenesis, spawning, and planula brooding by the reef coral Goniastrea aspera (Scleractinia) in Okinawa, Japan. Mar Ecol Prog Ser 151:67 72 Sammarco PW (1982) Polyp bail-out: an escap e response to environmental stress and a new means of reproduction in corals. Mar Ecol Prog Ser 10:57 65 Santangelo G, Carletti E, Maggi E, Bramanti L (2003) Reproduction and population sexual structure of the overexploite d Mediterranean red coral Corallium rubrum Mar Ecol Prog Ser 248:99 108 Schmutz SM, Boag DA, Schmutz JK (1979) Causes of the unequal sex ra tio in populations of adult Richardson's ground squirrels. Can J Zool 57:1849 1855 Shinkarenko L (1981) The natural history of fi ve species of octo-corals (Alcyonacea) with special reference to reproduc tion, at Heron Island Reef Great Barrier Reef. PhD dissertation, University of Queensland, St. Lucia Slattery M, Hines GA, Starmer J, Paul VJ (1999) Chemical signals in gametogenesis, spawning, and larval settlement and de fense of the soft coral Sinularia polydactyla Coral Reefs 18:75 84 Soong KY (1991) Sexual reproductive patterns of sh allow-water reef corals in Panama. Bull Mar Sci 49:832 846 Soong KY (1993) Colony size as a species character in massive reef corals. Coral Reefs 12:77 83 Soong KY, Lang JC (1992) Reproductive integr ation in reef corals. Biol Bull 183:418 431 Stearns SC (1976) Life history tactic s: review of ideas. Q Rev Biol 51:3 47

PAGE 84

84 Stenseth NC, Kirkendall LR (1985) On th e evolution of pseudogamy. Evolution 39:294 307 Stimson JS (1978) Mode and timing of reproduction in some common hermatypic corals of Hawaii and Enewetak. Mar Biol 48:173 184 Szmant AM (1986) Reproductive ecology of Caribbean reef corals Coral Reefs 5:43 53 Szmant AM, Gassman NJ (1991) Caribbean reef co rals: the evolution of reproductive strategies. Oceanus 11 18 Szmant-Froelich AM (1985) The effect of co lony size on the reproductive ability of the Caribbean coral Montastrea annularis (Ellis and Solander). Proc 5th Intl Coral Reef Symp 4:295 300 Tomascik T, Sander F (1987) Effects of eutrophication on reef-building corals. III. Reproduction of the reef-building coral Porites porites Mar Biol 94:77 94 Tsounis G, Rossi S, Aranguren M, Gili JM, Arnt z W (2006) Effects of spatial variability and colony size on the reproduc tive output and gonadal de velopment cycle of the Mediterranean red coral ( Corallium rubrum L.). Mar Biol 148:513 527 van Teeffelen AJA, Ovaskainen O (2007) Can the cau se of aggregations be inferred from species distributions? Oikos 116:4 16 Vermeij MJA (2005) Substrate composition and adu lt distribution determine recruitment patterns in a Caribbean brooding cora l. Mar Ecol Prog Ser 295:123 133 Ward S (1992) Evidence for broadcast spawning as well as brooding in the scleractinian coral Pocillopora damicornis Mar Biol 112:641 646 Warner ME, Fitt WK, Schmidt GW (1996) The effects of elevated temperature on the photosynthetic efficiency of zooxanthellae in hos pite from four differe nt species of reef coral: a novel approach. Plant Cell Environ 19:291 299

PAGE 85

85 BIOGRAPHICAL SKETCH A native Californian, Kate Lazar g rew up in the San Francisco Bay Area before heading south to the University of California, San Die go (UCSD), where she rece ived her Bachelor of Science degree in ecology, behavior, and evolu tion. While attending UCSD she traveled to Monteverde, Costa Rica, for an education abroad program, where she was introduced to tropical ecology. After graduating, Kate volunteered in Pa nama for a sea turtle research program, and then worked for the California Department of Fish and Game on their Pacific herring and California market squid research programs. In pr eparation for life on a graduate student salary, Kate also worked at REI, where they give great employee discounts on tents and sleeping bags. While researching squid fecundity, Kate was accepted into graduate school at the Department of Fisheries and Aquatic Sciences at the University of Florida (UF). She received her Master of Science in summer 2008. She is currently living in England and working as a freelance copy editor for several scientific journals.