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Genetic and Morphological Variation Between Populations of the Pascagoula Map Turtle (Graptemys gibbonsi) in the Pearl and Pascagoula Rivers with Description of a New Species
Abstract and Figures
Cryptic or undescribed species pose a major problem in conservation biology. Managing multiple unresolved taxa collectively as a single entity could precipitate the loss of unrecognized genetic variation and unique populations and, possibly, lead to extinction of undiscovered or unrecognized taxa. In contrast to other species in its clade, the Pascagoula map turtle (Graptemys gibbonsi), as currently recognized, is not confined to a single major river system (or a cluster formed by a major river and adjacent minor drainages) but occurs in two major river systems, the Pearl and Pascagoula Rivers. We analyzed G. gibbonsi samples from both rivers for the first time in a morphological and molecular assessment of the taxonomic status of this poorly studied species. We compared the extent of genetic differentiation (mitochondrial DNA; mtDNA) between G. gibbonsi populations with members within the pulchra clade and between Graptemys oculifera and Graptemys flavimaculata. We found significant carapace pattern variation and morphological differentiation between the Pearl and Pascagoula river samples of G. gibbonsi. Our mtDNA sequences showed greater genetic differentiation between G. gibbonsi samples from the Pearl and Pascagoula rivers than between two recognized and reciprocally sympatric species, G. oculifera (Pearl River) and G. flavimaculata (Pascagoula River), but revealed only a modest degree of differentiation when compared to other members of the pulchra clade. Based on the degree of differentiation in 1) morphology, 2) color patterns, and 3) mtDNA, in addition to their 4) allopatric distributions, we describe a new species from the Pearl River, restricting the species G. gibbonsi to the Pascagoula River.
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... Lovich and McCoy (1992) examined specimens from four river drainages and divided the species into three species, G. pulchra, G. ernsti, and G. gibbonsi, with the last of these inhabiting the Pascagoula and Pearl rivers of southern Mississippi and southeastern Louisiana. Later, Ennen et al. (2010) showed that the turtles in the Pascagoula and Pearl rivers were also separate species, describing those from the Pearl River drainage as a new species (G. pearlensis). ...
... barbouri, G. ernsti, and G. pulchra) is evidence of niche conservatism (Peterson et al. 1999;Peterson 2011). Graptemys pearlensis and G. gibbonsi are similar enough in appearance that they were considered conspecific until just a decade ago (Mount 1975;Lovich and McCoy 1992;Ennen et al. 2010), and phylogenetic analyses suggest they are each other's closest relatives (Praschag et al. 2017;Thomson et al. 2018). Hence, it is not surprising that they should have similar diets in adjacent, ecologically similar river systems. ...
Patterns of interspecific differences in the diets of nonavian reptiles may be complicated by intraspecific dietary diversity that is related to variation in body size and trophic morphology. Graptemys pearlensis and Graptemys gibbonsi are sister map turtle species endemic to adjacent Gulf Coastal river drainages and both are candidates for federal listing. Little has been reported about the diet of either species. We examined fecal samples collected from turtles captured throughout their respective ranges in the Pearl and Pascagoula river drainages. Females of both species primarily consumed invasive Asian clams (Corbicula spp.), with adult females being nearly exclusively molluscivorous while juvenile females also consumed softer-bodied prey items. Adult males and unsexed juveniles primarily consumed insects; males in particular specialized on trichopteran larvae and also ate more mollusks than did unsexed juveniles. In comparisons to each species' sympatric congeneric sawback species, the two focal species' avoidance of sponges caused large interspecific differences. Due to their greater consumption of insect prey than mollusks, unsexed juvenile G. pearlensis and unsexed juvenile and adult male G. gibbonsi were slightly more similar in diet to their respective sympatric congeneric sawbacks than to conspecific large juvenile females and adult females. Scoring of similarity in diet was greatly influenced by strongly predominant prey items found within each class of each species. Future studies of interspecific dietary differences in sympatric species should include consideration of intraspecific variation in diet as it relates to body size and sexual dimorphism.
... They designated 1 of the specimens from 1876 as lectotype and restricted the name G. pulchra to specimens from the Mobile Bay drainages, describing the Escambia Bay drainage specimens as Graptemys ernsti and the Pearl and Pascagoula river drainage specimens as G. gibbonsi; they also recognized some differences between specimens from the latter 2 rivers. Ennen et al. (2010) described the Pearl River drainage specimens as G. pearlensis, restricting G. gibbonsi to the Pascagoula River drainage specimens. Thomson et al. (2017) reported support for the monophyly of each of the 4 allopatrically distributed species formerly united as G. pulchra sensu lato. ...
... We believe it is clear that populations of G. gibbonsi are more robust overall than populations of G. pearlensis. A previous comparison of sawback:megacephalic species ratios in -1995(Lindeman 1998 did not consider the difference between the drainages because the 2 megacephalic species were at that time considered a single species under the name G. gibbonsi (Ennen et al. 2010). In replicated point counts conducted primarily on main stem sites (31 of 41 total sites, or 76%), the 2 sawbacks were 5.1 as abundant as the 2 megacephalics. ...
... oculifera; Baur 1890) and the Pearl Map Turtle (G. pearlensis; Ennen et al. 2010). Graptemys oculifera is listed as Threatened under the Endangered Species Act (USFWS 1986) and in Louisiana is considered State Threatened (S2) and a Tier 1 Species of Greatest Conservation Need (SGCN; Holcomb et al. 2015). ...
The Ringed Sawback (Graptemys oculifera) and the Pearl Map Turtle (G. pearlensis) are riverine turtles that are endemic to the Pearl River drainage of central Mississippi and southeastern Louisiana USA. Graptemys oculifera is listed as Threatened under the U.S. Endangered Species Act, and G. pearlensis was also recently proposed for Threatened status, yet most of the information on both species comes from the Mississippi portion of their range. During May/June 2020 and 2021, I assessed the status of both species in Louisiana using a combination of survey methods. Point count surveys detected both Graptemys primarily in the Bogue Chitto and Pearl rivers, with G. oculifera observations exceeding those of G. pearlensis. I documented Graptemys oculifera and G. pearlensis in 3 and 4 previously undocumented creeks, respectively. Basking density surveys at 22 sites were about 4.5× greater for G. oculifera (14/rkm) compared to G. pearlensis (3.1/rkm). Mark-resight population estimates at six sites for G. oculifera averaged 99/river km (rkm, range from 49-158/rkm), while G. pearlensis estimates at three sites averaged 10.6/rkm (range from 3-23/rkm). Lastly, trapping at six sites in 2020 and 2021 yielded a total of 111 G. oculifera and 14 G. pearlensis. In summary, G. oculifera appears secure in Louisiana, while G. pearlensis is rare and appears more sensitive to riverine modifications. Additional monitoring and enforcement efforts are needed in the future due to a myriad of threats for both species in the Pearl River system.
... The Checklist of Chelonians of the World (Fritz and Havaš 2007), the CITES Standard Reference, includes the proposed species G. barbouri, G. ernsti, G. gibbonsi and G. pulchra, with the exception of G. pearlensis, described in 2010 (Ennen et al., 2010). ...
CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) wasopened for signature in Washington DC on 3rd March 1973, and to date has 184 Parties from across the world. If CITES is to remain a credible instrument for conserving species affected by trade, the decisions of the Parties must be based on the best available scientific and technical information. Recognizing this, IUCN and TRAFFIC have undertaken technical reviews of the proposals to amend the CITES Appendices submitted to the Nineteenth Meeting of the Conference of the Parties to CITES (CoP19).
The Analyses - as these technical reviews are known - aim to provide as objective an assessment as possible of each amendment proposal against the requirements of the Convention, as agreed by Parties and laid out in the listing criteria elaborated in Resolution Conf. 9.24 (Rev. CoP17) and other relevant Resolutions and Decisions. To ensure the Analyses are as accessible as possible to all Parties, we have created a bespoke webpage where the Analyses can be downloaded individually by proposal or in full (see https://citesanalyses.iucnredlist.org/).
... These markers are practical and risk-free tools that can facilitate an accurate diagnosis. Comparative studies of the genetic variation described by molecular markers and regional morphometric patterns have centered on several wild turtle species [78]. The following molecular markers (Table 1) stand out among those used to detect genetic variability in DNA sequences, such as restriction fragment length polymorphism (RFLP), random amplified polymorphic DNA (RAPD), single nucleotide polymorphism (SNP), mitochondrial DNA (mtDNA), and microsatellites or short tandem repeats (STR) [79]. ...
Simple Summary
Turtles are threatened all over the world. Malaysia has 24 species of turtles. This review focuses on current conservation status and some requirements for sustainability. We propose integrating concepts of ecology and molecular biology to provide almost comprehensive turtle reviews in Malaysia.
Abstract
Approximately 356 species of turtles inhabit saltwater and freshwater habitats globally, except in Antarctica. Twenty-four species of turtles have been reported in Malaysia, four of which are sea turtles. The state of Terengganu harbored the highest number of turtles, with 17 different reported species. Based on the IUCN Red List, 29% of turtle species in Malaysia are critically endangered. In comparison, another 25% are classified as endangered. Likewise, CITES reported that 67% of Malaysia’s turtles are threatened, while 25% are classified as critically endangered. This review discusses the checklists, molecular genetics work, conservation status, recent trends, and recommendations for future research. Factors contributing to their population declines and current endangered status are also discussed.
... Although this genetic structure and morphological differentiation may be the result of genetic drift, little gene flow between Mississippi and Alabama populations may occur due to the large distance between the mouth of the Pascagoula River Delta and the Alabama populations. Land and saltwater can hinder gene flow for freshwater species that are distributed in riverine systems across the Gulf of Mexico (Soltis et al., 2006), including the Pascagoula River (e.g., Dugo et al., 2004;Ennen et al., 2010). level of tolerance to brackish water (Agha et al., 2018). ...
Pseudemys alabamensis is one of the most endangered freshwater turtle species in the United States due to its restricted geographic distribution in coastal Alabama and Mississippi. Populations of P. alabamensis are geographically isolated from one another by land and saltwater, which could act as barriers to gene flow. It is currently unknown how differentiated these populations are from one another and whether they have experienced reductions in population size. Previous work found morphological differences between Alabama and Mississippi populations, suggesting that they may be evolutionarily distinct. Other Pseudemys turtles such as P. concinna and P. floridana occur naturally within the same geographic area as P. alabamensis and are known to hybridize with each other. These more abundant species could threaten the unique genetic identity of P. alabamensis through introgression. In order to evaluate the endangered status of P. alabamensis and the level of hybridization with other species, we used mitochondrial and nuclear microsatellite markers to assess genetic variation within and among populations of P. alabamensis throughout its range and estimate admixture with co‐occurring Pseudemys species. In P. alabamensis, we found no variation in mitochondrial DNA and an excess of homozygosity in microsatellite data. Our results show genetic differentiation between Alabama and Mississippi populations of P. alabamensis, and low estimated breeding sizes and signs of inbreeding for two populations (Fowl River, Alabama and Biloxi, Mississippi). We also found evidence of admixture between P. alabamensis and P. concinna/P. floridana. Based on our results, P. alabamensis is highly endangered throughout its range and threatened by both low population sizes and hybridization. In order to improve the species’ chances of survival, focus should be placed on habitat preservation, maintenance of genetic diversity within both the Mississippi and Alabama populations, and routine population‐monitoring activities such as nest surveillance and estimates of recruitment. Pseudemys alabamensis is one of the most endangered freshwater turtle species in the United States. Populations of P. alabamensis are geographically isolated from one another by land and saltwater, which could act as barriers to gene flow, resulting in the evolution of unique populations. Other Pseudemys turtles such as P. concinna and P. floridana occur naturally within the same geographic area as P. alabamensis and are known to hybridize with each other. These more abundant species could threaten the unique genetic identity of P. alabamensis through introgression. We used mitochondrial and nuclear microsatellite markers to assess genetic variation within and among populations of P. alabamensis throughout its range and estimate admixture with co‐occurring Pseudemys species. We found that P. alabamensis is highly endangered throughout its range and threatened by both low population sizes and hybridization. Conservation measures must be developed to prevent further reduction and extinction of this endangered species.
... However, often the autors advocating for splits (e.g. Vog, 1993 for G. ouachitensis from G. pseudogeographica [see also discussion byFreedberg and Myer, 2012]; Lindeman 2013, for G. sabinensis from G. ouachitensis;Ennen et al. 2010 for another split in other Graptemys turtles) do not use the biological species concept. ...
The paper presents a review of literature data, supplemented with original observations, on the presence, establishment, distribution and invasive status of alien fish, amphibian and reptile species in Romania. Consistent criteria were followed in defining alien species records, establishment and invasive status. From the 48 alien fish species, 1 fish hybrid, 1 amphibian and 18 reptile species recorded, only 16 fishes and 3 reptiles can be regarded as established. Of these we consider the criteria for invasive status as being probably fulfilled by one fish species ( Perccottus glenii ), and less likely by six more fish species. The presence and the alien status of the one amphibian are debatable. No reptile species can be considered invasive at present.
... Nine species were described in the 20th century, including G. ernsti and G. gibbonsi in 1992 (Lovich and McCoy 1992). Another, G. pearlensis, was described in 2010 (Ennen et al. 2010) and G. sabinensis was formally elevated to a full species in 2013 (Lindeman 2013), following the suggestions of earlier researchers. Clearly, our knowledge of the diversity of this genus is still evolving and new species or distinct evolutionary lineages may yet be discovered and recognized. ...
It was just over 2 centuries ago that the first species of Graptemys (G. geographica) was described by the French naturalist Charles Alexandre LeSueur (1817; see also Lindeman 2009) under the “catch-all” turtle genus of the time, Testudo. The first use of the name Graptemys, applied by the Swiss-American naturalist Louis Agassiz, came 4 decades later (Agassiz 1857; etymology: Graptos—inscribed, painted; emys—turtle; named in reference to the distinctive map-like markings on the carapace). Aside from mostly taxonomic publications, literature on the natural history of the genus accumulated slowly for the next 130+ yrs after LeSueur's description. It was not until the 1950s that information about the genus started to increase rapidly, with the pioneering research of one of the co-founders of modern turtle ecology: Fred Cagle (Gibbons and Lovich 2019).
At Tulane University, Cagle was perfectly located near the center of Graptemys diversity along the northern Gulf of Mexico in New Orleans, Louisiana. Cagle and his research crews scoured the rivers of the southeastern United States looking for turtles, especially Graptemys (Lindeman 2013). The discovery of taxidermic mounts of 4 little-known species in a dusty back room at the university—display specimens collected in the late 1800s that had become forlorn remnants of a by-then long-defunct public museum—was the catalyst to investigate the group (Fig. 1). Cagle and his students were responsible for describing several new species, obtaining novel information on life history and ecology, and documenting the species' native river drainages. Up until that point, the provenance of most museum specimens was unknown or geographically dubious. For example, Baur (1890) had described G. oculifera from Mandeville, Louisiana, and Pensacola, Florida, but Cagle (1953) later found the species to be located only in the Pearl River system, ∼33 km east of Mandeville and ∼230 km west of Pensacola. Cagle was also the first to recognize the phenomenon of river endemicity in the genus and knew that “the evolutionary history of this complex is substantially different from that of other turtle species of the Gulf Coast” (Cagle 1954).
Figure 1
A taxidermic mount of a ringed sawback, Graptemys oculifera, from the Tulane University Museum collection (TU 27), collected in 1891 and on public display for several years thereafter. Rediscovery of specimens of G. oculifera, G. pearlensis, G. sabinensis, and G. pseudogeographica collected by Baur in the late 1800s catalyzed work on Graptemys of the Gulf Coast states by Cagle and his students in the late 1940s and 1950s. (Photo by P.V.L.)
We now know that the evolutionary history of the genus was likely shaped by historical sea-level changes and/or stream piracy events that drove dispersal and vicariant speciation events (Lamb et al. 1994). We also know that evolutionary diversification has occurred rapidly in the genus over the last 2 million yrs (Thomson et al. 2018). Now there are 14 recognized species of Graptemys (Lindeman 2013), making it the most speciose genus of turtles in the United States and one of the most diverse turtle genera in the world (Turtle Taxonomy Working Group 2017). Recognition of this diversity came relatively recently. Nine species were described in the 20th century, including G. ernsti and G. gibbonsi in 1992 (Lovich and McCoy 1992). Another, G. pearlensis, was described in 2010 (Ennen et al. 2010) and G. sabinensis was formally elevated to a full species in 2013 (Lindeman 2013), following the suggestions of earlier researchers. Clearly, our knowledge of the diversity of this genus is still evolving and new species or distinct evolutionary lineages may yet be discovered and recognized.
As measured by the number of peer-reviewed scientific publications concerning individual species, Graptemys are relatively poorly studied compared with the species of other turtle genera in the United States and Canada. The species with the largest number of peer-reviewed scientific publications in the genus, G. geographica, is not only the earliest described species, but also the widest-ranging species, and wide-ranging turtle species are typically the best studied in any genus (Lovich and Ennen 2013). Limited research attention likely stems from the difficulty Graptemys species present from a sampling and habitat perspective. As consumers of aquatic insect larvae, mollusks, sponges, and algae, they show little affinity for the traditional fish or fowl baits used in 3-hoop turtle nets, so alternative methods of catching them in order to record their data have had to be sought, such as fykenets, basking traps, and driving them into trammel nets with the use of a carphorn (Vogt 1980; Jones and Hartfield 1995; Lindeman 2014). These alternative traps capitalize upon map turtle and sawback movements throughout the water column and their drive, seemingly unmatched by other turtles, to climb out of the water and bask in the sun. Because of the turtles' basking proclivity, researchers have also benefitted enormously from the development of relatively inexpensive, high-power optical devices (e.g., image-stabilized binoculars, spotting scopes, and high-zoom cameras) that facilitate studies of relative abundance and vouchering of new locality records (e.g., McCoy and Vogt 1979; Lindeman 1999, 2013, 2019; Selman and Qualls 2009; Ilgen et al. 2014; Fig. 2). The medium to large rivers the species inhabit are also a challenge, requiring a boat with a motor and frequently consulting weather forecasts to avoid storms that may send river levels spiking one or more meters overnight, rendering trap retrieval nearly impossible.
Figure 2
Photo taken with a Nikon CoolPix zoom lens; first county record of Graptemys geographica in Susquehanna County, Pennsylvania, representing an upstream range extension of 84.8 river km over previously vouchered localities in the upper Susquehanna River (University of Flordia Museum of Natural History digital collection, UF 181006; Lindeman 2017). (Color version is available online.)
In contrast to catching adults, finding nests for reproductive studies is relatively easier. In the northern United States, thousands of nests of 3 sympatric species were often encountered in a single day on the sandbar islands in the Mississippi River, leading to landmark studies of temperature-dependent sex determination in turtles (Bull and Vogt 1979, 1981; Vogt and Bull 1984). These incubation experiments also led to the discovery that incubation temperatures affect head patterns in these species, helping to unravel the speciation problem in the Graptemys pseudogeographica complex (Vogt 1993).
Conservation interest in map turtles and sawbacks has increased greatly over the past 30 yrs. Two species, G. oculifera and G. flavimaculata, were federally listed as threatened under the Endangered Species Act (ESA) in 1986 and 1990, respectively. Since then, many other Graptemys have been considered for either state or federal protection status (reviewed in Lindeman 2013), including two species that are currently petitioned for federal ESA protection status (G. gibbonsi and G. pearlensis). From a conservation perspective, Graptemys is likely one of the most imperiled turtle groups in the United States. Declines have been documented for some species of Graptemys, and they all face continued threats to their survival, including human alterations to river systems (especially riverine impoundments, river regulation, and channelization), declines in water quality, and direct take for the pet trade.
Slowly, the species of Graptemys are getting their due, a transition that this special issue of Chelonian Conservation and Biology is meant to further catalyze. This issue reflects expanding interest in the genus among turtle biologists and makes an important contribution to our knowledge base, with topics focused on conservation, ecological research, and education. The 17 articles include new studies focused on 10 of the 14 recognized species of Graptemys, leaving out only G. caglei, G. ernsti, G. sabinensis, and G. versa.
Research topics in this issue run a wide gamut that covers both basic biology and conservation concerns. There are studies of various aspects of reproduction in Graptemys, including reproductive output and life-history strategies (Coleman, Lindeman), nest-site fidelity (Freed-berg, Nagle and Russell), and hatchling emergence (2 articles by Geller et al.). Dietary studies of half the species in the genus are included (the 3 sawbacks and their sympatric megacephalic congeners, McCoy et al.; G. barbouri, Sterrett et al.). One of the 5 turtle species included in a long-term data set for a lake in Indiana, investigated here for scute anomalies (G. Smith et al.), is a Graptemys species. A focus on geographic distribution is included with regard to new discoveries regarding natural range limits of 5 species in Mississippi (Brown et al., Lindeman et al.), anthropogenic impacts on waterways that appear to be allowing range expansion in 2 others (Berry et al.), and a Graptemys species acting as an introduced species (H. Smith et al.). The conservation focus includes a study of boating as a source of disturbance (Bulté et al.) and 3 articles involving extensive visual and/or trapping surveys (Lindeman et al., Mays and Hill, Selman), with 2 of these studies focusing on G. pearlensis and G. gibbonsi, which are currently candidates for federal listing. Finally, the interaction of Graptemys species with human communities is highlighted in an article using community scientists for data collection (Coleman) and an article examining the phenomenon of turtle watching in an urban park (Lindeman).
If the information reported in the articles included in this volume could be translated into concentrated education efforts, it could lead to increased local awareness and appreciation of these unique animals. Ultimately, we hope that research and education efforts in the coming decades lead to effective conservation of this truly unique group of North American turtles.
Acknowledgments
We thank Jeff Lovich and Richard Vogt for their comments on the drafting of this essay.
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... Two endemic riverine turtle species occur sympatrically in the Pearl River system of central Mississippi: Graptemys oculifera (ringed sawback; Baur 1890) and Graptemys pearlensis (Pearl map turtle; Ennen et al. 2010). Even though information has been collected for both species throughout the river system (e.g., Jones and Hartfield 1995;Lindeman 1998Lindeman , 1999Shively 1999;Selman and Jones 2017;Lindeman et al. 2020), there is relatively little population data for either species throughout the segment of the Pearl River that flows through downtown Jackson, including the section slated for the One Lake Project. ...
The impacts of human modifications of rivers and associated riverine fauna are well documented, especially following the construction of impoundments. In the Pearl River system of Mississippi and Louisiana, 2 endemic Graptemys species are found (G. oculifera; G. pearlensis), but little is known of their densities in urban segments near Jackson, Mississippi, even though both are species of conservation concern. I used spotting scopes and binoculars to complete replicated basking surveys for both Graptemys species during the summers of 2017 and 2018 in 5 equidistant segments of the Pearl River and nearby oxbow lakes. Basking densities for both species were generally higher in river segments upstream and downstream of Jackson compared to middle segments. Graptemys oculifera were found in greater densities than G. pearlensis in all segments (14–69-times higher). Graptemys oculifera was found in 4 of the 6 oxbow lakes surveyed, but mean densities decreased 10-fold compared with river segments; G. pearlensis was absent from all oxbow lakes. Densities for a generalist turtle species, Trachemys scripta, increased 35 times in oxbow vs. river habitats. The middle 3 survey segments (∼ 15.9 river kilometers) are inclusive of a proposed river impoundment project—the One Lake Project—for flood control and economic development. Estimates of direct and indirect impacts of this project are sizeable for G. oculifera (direct impact: 1684; indirect: 2129) while estimates for G. pearlensis are lower (direct: 88; indirect: 219). The One Lake Project would surely alter existing riverine processes and will favor generalist turtles such as T. scripta that prefer nonflowing lake settings at the expense of riverine Graptemys species. The One Lake Project would be a major setback to both Graptemys species in and around the project area and would negatively impact the recovery potential of both species.
Turtles are one of the most threatened group of animals in existence today. The
Southeastern United States is one of two global biodiversity hotspots for turtle species,
including the state of Mississippi, where over 30 species can be found. However, very
few studies have occurred within the state.
The overarching goal of this project was to perform a species inclusive freshwater
survey and document the distribution and abundances of the diverse species present here.
A substantial amount of data was collected through these surveys, including
morphometric measurements, genetic samples, and habitat data recorded at each trap
location. These data were then used to determine if riverine habitat and surrounding land
cover has any effect on turtle communities. Similarly, a state-wide population genetic
study on the Spiny Softshell turtle (Apalone spinifera) was initiated.
The surveys performed for this study captured a total of 1,230 turtles, from 16
species. Analyses showed that land-use had no significant impact on turtle communities
or species, but that habitat can be a predictor of species occurrence in some
circumstances. Finally, our genetic analysis of A. spinifera from the Pascagoula and Pearl
River drainages showed two distinct populations between the two drainages, but did not
detect any intra-drainage populations structure.
Three new species of Percina are described from upland drainages of the Mobile Basin. Two of the three species are narrowly distributed: P. kusha, the Bridled Darter, is currently known only from the Conasauga River drainage in Georgia and Tennessee and Etowah River drainage in Georgia, both tributaries of the Coosa River, and P. sipsi, the Bankhead Darter, which is restricted to tributaries of Sipsey Fork of the Black Warrior River in northwestern Alabama. The third species, P. smithvanizi, the Muscadine Darter, occurs above the Fall Line in the Tallapoosa River drainage in eastern Alabama and western Georgia. In a molecular analysis using mitochondrial cytochrome b sequence data, P. kusha and P. smithvanizi were recovered as sister species, while Percina sipsi was recovered in a clade consisting of P. aurolineata (P. sciera + P. sipsi). Two of the three species, P. kusha and P. sipsi, are considered to be imperiled species and are in need of conservation actions to prevent their extinction. Description of these three darters increases the number of described species of Percina to 44. Sixteen are known to occur in the Mobile Basin, including nine that are endemic.
We describe a new species of chorus frog of the North American treefrog genus Pseudacris from the south-central United States. This new species is morphologically similar to the parapatric species P. feriarum and has thus previously been considered synonymous with this species. The new species is geographically distinct from P. feriarum and from its sister species, P. nigrita. We diagnose the new species based on advertisement call, morphological, and genetic characters.
The recently-developed statistical method known as the "bootstrap" can be used to place confidence intervals on phylogenies. It involves resampling points from one's own data, with replacement, to create a series of bootstrap samples of the same size as the original data. Each of these is analyzed, and the variation among the resulting estimates taken to indicate the size of the error involved in making estimates from the original data. In the case of phylogenies, it is argued that the proper method of resampling is to keep all of the original species while sampling characters with replacement, under the assumption that the characters have been independently drawn by the systematist and have evolved independently. Majority-rule consensus trees can be used to construct a phylogeny showing all of the inferred monophyletic groups that occurred in a majority of the bootstrap samples. If a group shows up 95% of the time or more, the evidence for it is taken to be statistically significant. Existing computer programs can be used to analyze different bootstrap samples by using weights on the characters, the weight of a character being how many times it was drawn in bootstrap sampling. When all characters are perfectly compatible, as envisioned by Hennig, bootstrap sampling becomes unnecessary; the bootstrap method would show significant evidence for a group if it is defined by three or more characters.
Variation in relative width of the head and alveolar surfaces of the jaws in map turtles (Graptemys) is associated with the degree of molluscivory in adult females. Adult males are substantially smaller in body size and are primarily insectivorous, and they take few mollusks regardless of their relative head width or alveolar width. We assessed functional relationships within and between the sexes using comparative analyses (independent contrasts and squared-change parsimony) of the residuals of regressions of head width on plastron length and alveolar width on head width. Residuals of head width and alveolar width were significantly correlated within females but not within males in all comparative analyses. Residuals of each regression were significantly correlated between males and females for a subset of analyses. Our results suggest that evolutionary changes in relative head width have been correlated with changes in relative alveolar width in females of Graptemys due to a functional relationship that is related to the tendency to feed on mollusks. Males have exhibited changes in the two characters similar to changes in females over evolutionary time, probably as a result of genetic covariation, but due to males' primarily insectivorous nature, changes in the two characters have not shown significant correlation with one another.
Replicate adaptive radiations are dichotomous morphological patterns related to resource use and repeated in a series of isolated habitats. Biologists have long noted a dichotomy in relative head width and alveolar width among species of map turtles (Graptemys), particularly with regard to adult females, which are much larger than adult males in all 12 species. I measured plastron length (PL), head width (HW), and alveolar width (AW) of nearly 2300 specimens representing the 12 recognized species, and used allometric regressions to investigate this genus as an example of both sexual dimorphism in trophic morphology and replicate adaptive radiation. Sexual dimorphism was noted in HW after correction for PL, with females having wider heads than males of similar body sizes, but AW as corrected for HW was not dimorphic, thus absolute differences in AW are the simple result of differences in HW. Sexual differences in HW probably relate to the dimorphic niches of Graptemys, as females of three species have been reported to occupy deeper water further from shore than conspecific males. Based on predicted HW at maximum PL in adult females, species were categorized as mega-, meso-, or microcephalic. Differences in relative head width are related to differences in degree of molluscivory, with little molluscivory in microcephalic females, moderate to high molluscivory in mesocephalic females, and high molluscivory in mega-cephalic females. Distributions of Graptemys species in sympatry and allopatry reveal patterns consistent with structuring of distributions via competitive interactions. Superimposing data on relative HW on a phylogeny of the genus suggests there may have been one or two episodes of character displacement, with subsequent character assortment, in Graptemys evolution. This conclusion is similar to the current model for the evolution of body size during the radation of Anolis lizards in the northern Lesser Antilles.
From June 1969 until October 1972 the natural history of the Alabama map turtle, Graptemys pulchra, was studied in southern Alabama. Over 500 specimens were collected, of which 286 were measured, marked, and released, and 91 were autopsied for reproduction and food studies. Graptemys pulchra was the most abundant turtle in the study area and its primary food item, the imported oriental mussel Corbicula maniliensis, was the most abundant macro-invertebrate. Large, mature individuals of G. pulchra were more abundant than juveniles. Home range was apparently more stable in males, but only females exhibited homing behavior. I found that females either returned to the home area or remained at the displacement site. Those returning to their original localities moved distances of 24 river channel km (15 mi) or more up- and downstream. Growth is rapid in juveniles but declines sharply at maturity and approaches zero shortly after maturity. Males reach sexual maturity in their third or fourth year, but females apparently do not reach maturity until they are approximately 14 years old. Maximum size in females is reached in about 23 years, and natural longevity probably exceeds 50 years. Sexual dimorphism with respect to size is pronounced, the largest male studied being about half the carapace length of the smallest female (120 mm vs 212 mm). Although sperm were present in the male reproductive tract throughout the year, mating behavior was observed only in autumn months, suggesting that sperm is stored in females. The male courtship sequence is similar to that described for other aquatic emydines, except that the "titillation tool" of the male is the snout, rather than elongate fore-claws. Elongate fore-claws are not characteristic of adult males. Predation probably resulted in the destruction of 95 percent of the natural nests during the study period, although some reproductive seasons were much more successful than others. The major diurnal predator on nests was the fish crow, and the major nocturnal predator was the raccoon. The only significant ehemies of adults are man and possibly the alligator snapping turtle, Macroclemys temmincki. Reproductive potential vafied from 7 to 71, depending on the size of the female, and averaged 29 eggs per season per female. An average of 4 (1-6) clutches were laid per season per female. Extra-uterine migration of ova was usual. Nests were located 1-20 m from the water's edge, usually on large, exposed sandbars. Coarseness of the sand seemed to be the major criterion on which nest site selection was based. Incubation required from 74 to 79 days at 29°C, the average nest chamber temperature in natural nests. Infertility of individual eggs and entire clutches was common. Males and females under 100 mm carapace length were primarily insectivorous, whereas juvenile and adult females in the study area subsisted almost entirely on Corbicula. Feeding generally began in May and ended in October. Since growth ceased in early September, food assimilated during September and October was probably stored for winter. The most significant determinant of seasonal activity was water temperature. Activity and feeding decreased sharply at water temperatures below 19°C (66°F). Complete inactivity (hibernation) of the entire, population during the winter was not observed. No significant interspecific competition with other turtle species was found.