Pond Turtles of Asia

In an earlier post on this site, I discussed some members of the tortoise family Testudinidae. In popular depictions, the terrestrial tortoises are commonly associated with arid deserts and Mediterranean climes, where rains are sparse and water bodies few. But tortoises are exceptional in this regard among the order Testudines, members of which are more generally aquatic. As an example, consider the closest relatives of the Testudinidae, the pond turtles of the Geoemydidae.

Southern river terrapin Batagur affinis, copyright Eng Heng Chan.

Members of the Geoemydidae (historically referred to in many publications as the Bataguridae) are commonly referred to as the Asiatic pond turtles and it is in southern and eastern Asia that they are most diverse. However, they are also found in Europe and northern Africa, and a single genus Rhinoclemmys is found in northern South America. About 65 or 70 species are recognised in the family, making them quite diverse as turtles go. Many geoemydids are colorfully patterned and some can reach reasonably large sizes. The northern river terrapin Batagur baska, for instance, may grow up to two feet in length and close to twenty kilograms in weight.

Black-breasted leaf turtle Geoemyda spengleri, copyright Heather Paul.

A phylogenetic analysis of the Geoemydidae by Hirayama in 1984 lead to the suggested division of the geoemydids between two subfamilies, the Geoemydinae and Batagurinae. The two subfamilies were primarily distinguished by the extent of development of the secondary palate and hence the width of their jaws, with the Batagurinae having a more extensive secondary palate and broader jaws than the Geoemydinae. Batagurines were also generally more aquatic and more herbivorous than the semi-terrestrial, more omnivorous geoemydines. Hirayama also suggested that the geoemydines might be paraphyletic to the Testudinidae (Spinks et al. 2004). More recent phylogenetic analyses have supported geoemydid monophyly, placing them as sister rather than ancestral to Testudinidae (Spinks et al. 2004; Guillon et al. 2012). They have also supported a clade including the majority of Hirayama's batagurines, excluding only the genus Siebenrockiella. However, Hirayama's geoemydines have not been supported as monophyletic; instead, the Neotropical Rhinoclemmys represents the sister group of the Old World geoemydids. This is not entirely surprising; comparison with other turtle families indicates that the narrow-jawed 'geoemydine' condition is primitive among turtles. As a result, the Batagurinae is no longer recognised as a distinct subfamily.

Golden coin turtle Cuora trifasciata, copyright Torsten Blanck.

Unfortunately, the Asian species of pond turtle are currently facing a conservational crisis. The majority of species are regarded as endangered, many critically so, due to threats such as habitat loss and hunting for food. Some species, most notably the golden coin turtle Cuora trifasciata, are targeted for use in Chinese medicine because why wouldn't they be? Many geoemydid species have been bred in captivity but this is also not without issues. In the case of the golden coin turtle, there is the all-too-common issue that even when farmed individuals are available they are not seen as being as valuable as wild-caught specimens. Also, because the gender of hatchlings is determined by incubation temperature, farmed clutches are skewed almost entirely towards females, requiring the continued harvesting of wild males. Many geoemydid species hybridise readily. During the period from 1984 to 1997, no less than thirteen new species of geoemydid were described from China, most on the basis of specimens purchased from a single pet dealer in Hong Kong (Parham et al. 2001). Many of these specimens were of uncertain origin. Searches for further specimens in reported localities for some species failed to provide results, and queries to local residents revealed that they had never seen such turtles. At least some of these supposed new species have since been identified as hybrids, probably produced in captivity, and the status of others remains questionable.

REFERENCES

Guillon, J.-M., L. Guéry, V. Hulin & M. Girondot. 2012. A large phylogeny of turtles (Testudines) using molecular data. Contributions to Zoology 81 (3): 147–158.

Parham, J. F., W. B. Simison, K. H. Kozak, C. R. Feldman & H. Shi. 2001. New Chinese turtles: endangered or invalid? A reassessment of two species using mitochondrial DNA, allozyme electrophoresis and known-locality specimens. Animal Conservation 4: 357–367.

Spinks, P. Q., H. B. Shaffer, J. B. Iverson & W. P. McCord. 2004. Phylogenetic hypotheses for the turtle family Geoemydidae. Molecular Phylogenetics and Evolution 32: 164–182.