Genetic Diversity of the Critically Endangered Big-Headed Turtle (Platysternon megacephalum) Based on Wild and Traded Samples: Implications for Conservation

Abstract

Overexploitation has driven catastrophic declines in most turtle species in Asia. Many turtles are seized annually by law enforcement officers; unfortunately, seized turtles often lack associated information on their provenance. There is also taxonomic confusion regarding the clear delineation of turtle species and subspecies in Asia. This lack of provenance data and taxonomic uncertainty is problematic as it may preclude release, make appropriate release sites hard to select, or result in genetic pollution when animals are released. In this study, we amassed and analyzed the largest number of genetic samples of the critically endangered big-headed turtle (Platysternon megacephalum) to date. Our phylogenetic and network results based on nearly 500 sequences of a mitochondrial ND4 fragment corroborate the earlier hypothesis that only two of the three currently recognized subspecies have strong molecular support and that there is greater genetic structuring within one subspecies than has been previously reported. The vast majority of P. megacephalum confiscated from the trade in Vietnam belong to Subclade 3 of P. m. peguense, and this subclade is the most broadly distributed taxon of the big-headed turtle in Vietnam based on samples with known localities. Nonetheless, for the other two subclades, all their samples originate from the trade and could not be assigned to any geographic provenance because of the lack of wild-caught samples. In addition, our results reveal two trade centers of the species, Quang Ninh Province on the border between China and Vietnam and Kon Tum Province in the Central Highlands. However, smaller animal seizures occur across the range of the species in Vietnam. While the data presented here have facilitated the selection of appropriate release sites for confiscated P. megacephalum, the significant costs of genetic screening and the shortage of samples from wild animals with good localities hinder the rewilding efforts, especially for conservation practitioners working in countries where conservation activities are not well funded and research on poorly studied species is still limited. Nevertheless, we urge that wildlife translocations include robust pre-translocation genetic screening to ensure that all individual animals are reintroduced at appropriate sites.