|The Mekong Mud Snake, Enhydris subtaeniata. JCM|
From the mid-19th century to the mid-20th century it was popular to lump species, placing names in synonymies of older names if there was reason to suspect they might be the same species. With snakes, characters like similar scale rows at mid-body, similar color patterns, combined with similar distributions resulted in species named by one person being placed in the synonymy of another species by somebody else. The result, zoologists in the early 20th century greatly underestimated animal diversity. Such was the case of the Mekong Mud Snake, Enhydris subtaeniata. Rene Bourret described Hypsirhina enhydris subtaeniata in an obscure French colonial journal (Bulletin General de l'Instruction Publique) in French Indochina (Vietnam), in 1943 Malcolm Smith placed the name in the synonymy of Enhydris jagorii. However, it was recognized by Murphy (2007) as a valid species of the genus Enhydris, and established as a member of the enhydris clade based on molecular work (Karns et. al. 2010).
As its name suggests, the Mekong Mud Snake is endemic to the middle and lower Mekong drainage, but also occurs at Bung Boraphet in central Thailand. It is a highly aquatic, fishing eating snake they reaches high population densities at some locations. In a new paper Vimoksalehi Lukoschek and colleagues (2011) report high genetic diversity in Enhydris subtaeniata between seven sampled localities, while genetic diversity was low within each sampled locality. The authors suggest the diversity is the result of genetic isolation of populations by changes in the Quaternary landscapes of Indochina and that the snake was able to colonize central Thailand using corridors of ancient, now drowned river valleys.
Karns, D. R., Lukoschek, V., Osterhage, J., Murphy, J, C., and Voris, H. K. (2010) Phylogeny and biogeography of the Enhydris clade (Serpentes: Homalopsidae). Zootaxa, 2452. pp. 18-30. ISSN 1175-5334.
Lukoschek, V., Osterhage, J. L., Karns, D. R., Murphy, J. C. and Voris, H. K. (2011), Phylogeography of the Mekong mud snake (Enhydris subtaeniata): the biogeographic importance of dynamic river drainages and fluctuating sea levels for semiaquatic taxa in Indochina. Ecology and Evolution. doi: 10.1002/ece3.29
Murphy, J. C. 2007. Homalopsid Snakes, Evolution in the Mud. Krieger Publishing, Malabar, FL.