Preliminary genetic assessment of geographically distant populations of the giant freshwater stingray, Urogymnus polylepis (syn. Himantura chaophraya), calls for taxonomic re-examination

Abstract

The giant freshwater stingray, previously classified as Himantura chaophraya Monkolprasit & Roberts 1990, has been re-named as Urogymnus polylepis. Populations of this species have been reported in Indonesia, Myanmar, Bangladesh, and India, while the populations in Thailand have been reported in three rivers draining the Central Plains and the Mekong River. The presence of two different names in Thai documents has led to confusion in legislative references. To clarify the difference between these names, we employed molecular markers to examine genetic differentiation among geographically distant populations. Our findings revealed a large genetic divergence between the populations in Thailand and U. polylepis of the Indian Subcontinent and Greater Sunda Islands. This level of differentiation is worth a re-examination of biological characteristics of these stingrays. The additions of samples from Indonesian islands, Myanmar, Bangladesh, and India, along with the examination of more molecular markers should allow the clarification of the taxonomic relations of U. polylepis and U. chaophraya. Such efforts will benefit conservation protection of all giant freshwater stingray populations throughout their distribution ranges.