Graptemys Oculifera Research Articles

A Sawback is a Sawback is a Sawback: Diet and Habitat-Related Variation in Body Size of the Turtle Graptemys oculifera Show It Is an Ecological Analogue of Its Two Closest Relatives

A Sawback is a Sawback is a Sawback: Diet and Habitat-Related Variation in Body Size of the Turtle Graptemys oculifera Show It Is an Ecological Analogue of Its Two Closest Relatives

River Turtles and One Dam Lake: Two Imperiled Graptemys Species in the Pearl River and Potential Impacts of the Proposed 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.

Ecology of Riverine Turtle Communities in the Southern United States: Food Resource Use and Trophic Niche Dimensions

As part of an integrated study of the ecology of freshwater riverine turtle communities in the southern United States, we analyzed food resource partitioning in the turtle communities of the Cahaba, Chickasawhay, and Pearl rivers. We collected turtles with an array of unbaited fyke nets for periods of 10 d from 1 July to 13 August 1978 and 30 April to 4 August 1979, capturing 2707 turtles of 16 species in 2428 trap days. We successfully flushed the stomach contents from 729 turtles of the following species: Apalone mutica, Apalone spinifera, Graptemys flavimaculata, Graptemys gibbonsi, Graptemys nigrinoda, Graptemys oculifera, Graptemys pearlensis, Graptemys pulchra, Pseudemys concinna, Sternotherus carinatus, Sternotherus peltifer, and Trachemys scripta. We also caught 4 other species in low numbers: Chelydra serpentina, Graptemys pseudogeographica kohnii, Macrochelys temminckii, and Sternotherus odoratus. Stomach contents were identified and quantified by volume and percentage of occurrence for each species from each river. Food items were identified and placed in 6 categories: crustaceans, insects, mollusks, fish, plants, and unidentified. Pseudemys concinna was the most specialized feeder at all 3 sites, feeding almost exclusively on plants, followed by the wide-headed Graptemys and then narrow-headed Graptemys. Specialist species tended to show extensive niche overlap with any other species that consumed a large proportion of the specialists' preferred foods.

Three's Company: Observations of a Nonnative Map Turtle (Graptemys pseudogeographica) Occurring Syntopically with Two Endemic Graptemys in the Pearl River, Mississippi

Humans commonly move turtles and tortoises across geopolitical and geographic boundaries through food markets and the pet trade. One group commonly encountered in the pet trade is the genus Graptemys (map turtles and sawbacks). In the late 1980s, Graptemys pseudogeographica (false map turtle) was documented outside of its native range in the Pearl River near Jackson, Mississippi. Through replicated visual surveys in 2017 and 2018, we found that G. pseudogeographica persists in this location, but their densities were low (0.22/river km; 0.5% of all observations) compared with the 2 native Graptemys species. We evaluated the historical avenues for introduction via natural or human-mediated routes. Based on topographic profiles and historical hydrologic records, we strongly refute a prior hypothesis that G. pseudogeographica naturally colonized the Pearl from a neighboring drainage during the Easter Flood of 1979. Rather, we suggest that introduction via the release of unwanted pets is a more parsimonious conclusion. Because the lineage is shallowly diverged on an evolutionary scale, it seems possible that hybridization could occur between introduced G. pseudogeographica and Graptemys oculifera. Consequently, genetic introgression of the nonnative G. pseudogeographica genome is a possible threat to G. oculifera, a federally threatened species. This is a conservation concern to be further evaluated.

Population Status of the Megacephalic Map Turtles Graptemys pearlensis and Graptemys gibbonsi and Recommendations Regarding Their Listing Under the US Endangered Species Act

The Pascagoula map turtle (Graptemys gibbonsi) and Pearl map turtle (Graptemys pearlensis) were first separated from the Alabama map turtle (Graptemys pulchra) in 1992 under the former name and subsequently recognized as 2 separate species in 2010. The possibility that they should be listed under the Endangered Species Act was raised 7 yrs after separation from G. pulchra, when basking surveys showed that at most sites they were considerably less abundant than 2 sympatric congeners listed as threatened: the Pearl River drainage's ringed sawback (Graptemys oculifera, listed in 1986) and the Pascagoula River drainage's yellow-blotched sawback (Graptemys flavimaculata, listed in 1991). Historical data also indicated that the sympatric species pairs may once have been more similar in abundance. Now, more than 2 decades later, G. gibbonsi and G. pearlensis are candidates for listing. From 2015 to 2018, we surveyed basking turtles in point counts and in jon boat and canoe surveys and conducted trapping at several sites to ascertain the status of the 2 candidate species. Data were also combined with similar data collected between 2006 and 2014. Despite their similarity morphologically and in their basic ecology, 3 important differences are pertinent to the question of whether the 2 candidate species should be federally protected. First, their river systems are geomorphically very different. The medium-size to large tributary streams that the 2 species inhabit are a considerably more prominent feature of the Pascagoula drainage than the Pearl drainage and may insulate populations from potential threats on the main stems. Second, G. gibbonsi inhabited 35% more stream reach, had 22% higher catch per unit effort, and were recorded at 44% higher numbers in point counts and 3% higher numbers in basking density surveys than G. pearlensis. Coarse-scale estimates of each species' global populations suggest that G. gibbonsi is ∼ 1.56 times as abundant as G. pearlensis overall. Third, the reasons for the listing of each species' sympatric sawback congener are very different: G. oculifera of the Pearl drainage was listed primarily due to existing and imminent but as-yet-unrealized habitat modification, while G. flavimaculata of the Pascagoula drainage was listed primarily due to perceived low populations, particularly in upper portions of the drainage, and concerns regarding water quality. We conclude that G. pearlensis warrants conservation protection via a listing as threatened, while G. gibbonsi should be listed either as threatened or as threatened by similarity of appearance. For G. gibbonsi, the former option would recognize a long-term historical decline in its relative abundance suggested by trapping data from the 1950s through 1970s, while the latter would recognize its less imperiled status and protect it from the pet trade while focusing recovery efforts on G. pearlensis.

Impact of human disturbance on the thermoregulatory behaviour of the endangered ringed sawback turtle (Graptemys oculifera)

Abstract Human recreational disturbance of riverine environments may be contributing to population declines of aquatic organisms worldwide. Aquatic turtles that are heavily dependent on basking in sunlight to maintain an optimal body temperature may abandon basking perches because they perceive humans as potential predators. The impact of boat traffic, the availability of basking structures, and various environmental factors on the basking behaviour of the ringed sawback turtle (Graptemys oculifera) was assessed at two sites on the Pearl River, Mississippi, USA. This information was used to model the likely effects of human disturbance on the body temperature of large female turtles. Both the duration of basking and the percentage of turtles in a basking group that abandoned their basking perch were influenced by the availability of alternative basking sites, frequency of boat traffic, boat speed enforcement zones (‘wake’ or ‘no wake’), boat type, air temperature, weather conditions, and Julian day. A simulation model of anthropogenically disturbed and undisturbed adult female ringed sawbacks showed that disturbance probably decreases the mean daily body temperature, especially at higher disturbance probabilities and in May, when the air temperature is low. Management recommendations are provided that minimize the adverse effects of unintentional human disturbance of the ringed sawback to enable more effective conservation of this endangered, endemic species. Such methods are likely to be useful elsewhere as recreational disturbance becomes a greater conservation issue worldwide.

Long-Term Trends in Ringed Sawback (Graptemys oculifera) Growth, Survivorship, Sex Ratios, and Population Sizes in the Pearl River, Mississippi

Effective management of long-lived species requires demographic and life-history data that are best acquired from long-term studies. The ringed sawback (Graptemys oculifera), endemic to the Pearl River watershed of Mississippi and Louisiana, is a species of management concern at both the state and federal levels. Population sizes, trapping success, basking counts, sex ratios, survivorship, and growth of this species were investigated at 5 sites on the Pearl River in Mississippi over a 25-yr period. Estimates of age at maturity were 4.6 yrs for males and 9.1 yrs for females. Mean annual survivorship estimates for males, females, and juveniles were 0.88, 0.93, and 0.69, respectively. Maximum longevity estimates were 48.8 yrs for males and 76.4 yrs for females. Average longevity estimates were 8.5 yrs for males and 13.9 yrs for females. The sex ratio of captured turtles was male-biased before 2000 but unbiased after 2000. Realized population growth estimates indicated that 4 populations were stable over the 25-yr period and 1 population had declined. Population estimates and basking counts trended downward through time at most sites. Trapping success after 2000 for all sites combined declined by 77%, 45%, and 25% for juveniles, males, and females, respectively. Taken together, these data indicate that 1 population of G. oculifera has declined, 3 appear to be in the initial stages of decline, and 1 is relatively stable. Additional monitoring of these populations will be necessary to determine if these trends continue into the future.

Population Structure, Status, and Conservation of TwoGraptemysSpecies from the Pearl River, Mississippi

Abstract Graptemys is one of the least studied turtle genera in North America. Graptemys oculifera (Ringed Sawback) and Graptemys pearlensis (Pearl Map Turtle) are endemic to the Pearl River system of Mississippi and southeastern Louisiana. We studied both species near Columbia, Mississippi, on the Pearl River via a trapping and basking surveys over two years. Additionally, five sites including Columbia were trapped for 27 years to determine long-term trends in capture success and relative abundance (RA). At the Columbia site, body size distribution was bimodal for G. oculifera and atypically unimodal for G. pearlensis; G. pearlensis body lengths were smaller than museum specimens. Population estimates for G. oculifera at the Columbia site indicate a stable population over 25 years. Long-term RA trends indicated that G. pearlensis was less common than G. oculifera in all periods and at all sites from 1988 to 2013. Trends in long-term capture success for G. oculifera and G. pearlensis were negative at all ...

High Connectivity Observed in Populations of Ringed Sawbacks,Graptemys oculifera, in the Pearl and Bogue Chitto Rivers Using Six Microsatellite Loci

Graptemys oculifera is endemic to the Pearl River drainage system in Louisiana and Mississippi, and due to this limited range it is vulnerable to environmental changes. Many impacts to this drainage system are due to anthropogenic activities, and alterations may negatively impact the connectivity among populations of G. oculifera. Previous studies show populations below the Ross Barnett Reservoir might be undergoing population declines, suggesting limited movement among populations. In addition to anthropogenic effects, the drainage geomorphology might also play a role in shaping population connectivity, as the sister species of G. oculifera, G. flavimaculata, contains two distinct populations (mainstem Pascagoula and Escatawpa River) and possible subpopulations within the Pascagoula (upper Leaf River, upper Chickasawhay River, and lower sections of the Pascagoula River). We used six polymorphic microsatellite loci to analyze the population genetics of G. oculifera at eight sites in the Pearl River draina...

Intersexual allometry differences and ontogenetic shifts of coloration patterns in two aquatic turtles, Graptemys oculifera and Graptemys flavimaculata.

Coloration can play critical roles in a species' biology. The allometry of color patterns may be useful for elucidating the evolutionary mechanisms responsible for shaping the traits. We measured characteristics relating to eight aspects of color patterns from Graptemys oculifera and G. flavimaculata to investigate the allometric differences among male, female, and unsexed juvenile specimens. Additionally, we investigated ontogenetic shifts by incorporating the unsexed juveniles into the male and female datasets. In general, male color traits were isometric (i.e., color scaled with body size), while females and juvenile color traits were hypoallometric, growing in size more slowly than the increase in body size. When we included unsexed juveniles in our male and female datasets, our linear regression analyses found all relationships to be hypoallometric and our model selection analysis found support for nonlinear models describing the relationship between body size and color patterns, suggestive of an ontogenetic shift in coloration traits for both sexes at maturity. Although color is critical for many species' biology and therefore under strong selective pressure in many other species, our results are likely explained by an epiphenomenon related to the different selection pressures on body size and growth rates between juveniles and adults and less attributable to the evolution of color patterns themselves.

A quantitative analysis of the state of knowledge of turtles of the United States and Canada

The “information age” ushered in an explosion of knowledge and access to knowledge that continues to revolutionize society. Knowledge about turtles, as measured by number of published papers, has been growing at an exponential rate since the early 1970s, a phenomenon mirrored in all scientific disciplines. Although knowledge about turtles, as measured by number of citations for papers in scientific journals, has been growing rapidly, this taxonomic group remains highly imperiled suggesting that knowledge is not always successfully translated into effective conservation of turtles. We reviewed the body of literature on turtles of the United States and Canada and found that: 1) the number of citations is biased toward large-bodied species, 2) the number of citations is biased toward wide-ranging species, and 3) conservation status has little effect on the accumulation of knowledge for a species, especially after removing the effects of body size or range size. The dispersion of knowledge, measured by Shannon Weiner diversity and evenness indices across species, was identical from 1994 to 2009 suggesting that poorly studied species remained poorly-studied species while well-studied species remained well studied. Several species listed as threatened or endangered under the U.S. Endangered Species Act (e.g., Pseudemys alabamensis, Sternotherus depressus, and Graptemys oculifera) remain poorly studied with the estimated number of citations for each ranging from only 13-24. The low number of citations for these species could best be explained by their restricted distribution and/or their smaller size. Despite the exponential increase in knowledge of turtles in the United States and Canada, no species of turtle listed under the Endangered Species Act has ever been delisted for reason of recovery. Therefore, increased knowledge does not necessarily contribute appreciably to recovery of threatened turtles.

Growth in Kyphotic Ringed Sawbacks,Graptemys oculifera(Testudines: Emydidae)

Kyphosis has not been reported in any Graptemys species (map turtles and sawbacks). We captured four kyphotic individuals of Graptemys oculifera from the Pearl River system, Mississippi, with three individuals recaptured 5 to 12 yrs later; one juvenile female had measurable growth, and two adult females had negligible growth. All kyphotic individuals were females, with an overall occurrence rate of 0.10% (4 of 3830 individuals) at five G. oculifera sample sites.

Morphological and Molecular Reassessment of Graptemys oculifera and Graptemys flavimaculata (Testudines: Emydidae)

The turtle genus Graptemys consists of 15 recognized taxa, distinguished largely on the basis of pigmentation pattern (i.e., soft tissue and shell), head size, and shell morphology. However, phylogenetic studies have shown limited sequence divergence within the genus and between Graptemys oculifera and Graptemys flavimaculata relative to most other members of the Emydidae. Graptemys oculifera of the Pearl River drainage and G. flavimaculata of the Pascagoula River drainage have been recognized as species since 1890 and 1954, respectively. However, the description of G. flavimaculata was based on a limited number of morphological characters. Several of these characters overlap between G. flavimaculata and G. oculifera, and no attempt was made to test for significant morphological differentiation. In this study, we reevaluated the morphological and genetic distinctiveness of G. flavimaculata and G. oculifera with (1) multivariate statistical analyses of 44 morphological characters and (2) 1,560 bp of sequence data from two mitochondrial genes (control region and ND4). The morphological and molecular analyses produced incongruent results. The principal components analysis ordinations separated the two species along a pigmentation gradient with G. flavimaculata having more yellow pigmentation than G. oculifera. Likewise, clustering analyses separated the specimens into two distinct groups with little overlap between the species. Our mitochondrial data supported previous findings of limited genetic differentiation between the two species. However, the results of our morphological analyses, in conjunction with recently published nuclear gene sequence data, support the continued recognition of the two species.

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 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 pat...

Reproduction and Nesting of the Endangered Ringed Map Turtle, Graptemys oculifera, in Mississippi

Reproduction and nesting in the ringed map turtle (Graptemys oculifera) were investigated in the Pearl River of west-central Mississippi in 1995 and 1996. Nesting occurred from mid-May until mid-July but peaked in mid-June. Minimum carapace length of females at sexual maturity was 130 mm, but mean size at maturity was between 130 and 140 mm. Mean and modal CSs were 3.7 and 3. Larger females were gravid earlier than smaller ones and both egg and CS declined as the nesting season progressed. CS was positively correlated with both female carapace length and body mass. Mean egg length, width, and mass were 38.8 mm, 22.7 mm, and 11.8 g, respectively. Hatchlings averaged 35.5 mm carapace length and 8.9 g in mass. Annual clutch frequency may range from 0.96 to 1.42, and a minimum of ca. 60% of females reproduced on an annual basis. Predators destroyed an average of 86% of nests each year. Major vertebrate nest predators were armadillos, raccoons, and fish crows. Invertebrate egg predators destroyed an additional 24% of eggs known to be fertile.

Population Size and Growth in the Turtle Graptemys oculifera

Population sizes of Graptemys oculifera were estimated using two mark-recapture proce- dures at five sites on the Pearl River in Mississippi. These were compared with density estimates from basking counts at the same sites to determine if the latter could be used as indices of population size. Density estimates from the mark-recapture studies ranged from 85 to 341 G. oculifera per river km. Jolly- Seber and Schnabel population estimates were similar at three sites, but low numbers of recaptures resulted in inflated Jolly-Seber estimates at the two remaining sites. The Schnabel mark-recapture model appeared to be better suited for estimating population sizes of G. oculifera. Basking surveys provided a rough index to population sizes, but comparisons between sites were potentially complicated by differential wariness of basking turtles. Growth curves were constructed for each sex by fitting data from recaptured turtles to the von Bertalanffy and logistic growth models. The former model provided a better fit to the data than did the latter. Juveniles of both sexes grew at approximately the same rate. Males matured at 3.5 yr of age and females between 10 and 16 yr. Sex ratios were biased toward males at all sites. The ringed map turtle (Graptemys oculifera) is endemic to the Pearl River of Mississippi and Louisiana where it is restricted primarily to the main channel of the river and to the lower

Aspects of ecology of the threatened ringed sawback turtle, Graptemys oculifera

AbstractThe ringed sawback turtle, Graptemys oculifem, is endemic to the Pearl River system of Louisiana and Mississippi in southern USA. In 1986 the species was placed on the U.S. Federal List of Endangered and Threatened Species with status designation of 'threatened'. Existing museum specimens were examined to determine geographic distribution, food, growth and reproduction. Caddisflies, dipteran flies, mayflies, beetles and plant material were the most important food. Many stomachs contained small pieces of wood, suggesting that fallen tree trunks were a "grazing" substrate. Males ranged from 3.2-8.6 cm plastron length, and attained sexual maturity during the third or fourth year at lengths of about 6.0-7.0 cm. Adult males experienced recrudescence of testes, with maximum testis lengths during August and September indicating the probable time of spermatogenesis. Females ranged from 3.3-18.9 cm plastron length, and appeared to attain sexual maturity during the seventh or eighth year at lengths greater than 10.0 cm. The data suggested that ovulation occurs from May through July, nesting during June and ,July, and hatching at least during August. Clutch size appeared to be just two or three eggs.