Friday, April 8, 2016

[Herpetology • 2016] Malayemys khoratensis | Khorat Snail-eating Turtle • Integrative Taxonomy of Southeast Asian Snail-Eating Turtles (Geoemydidae: Malayemys) Reveals A New Species and Mitochondrial Introgression

Khorat Snail-eating Turtle |  Malayemys khoratensis
 Ihlow, Vamberger, Flecks, Hartmann, Cota, Makchai, Meewattana, Dawson, Kheng, Rödder & Fritz, 2016

Male specimen of Malayemys khoratensis from Sikhio, northeastern Thailand
photo: F. Ihlow


Based on an integrative taxonomic approach, we examine the differentiation of Southeast Asian snail-eating turtles using information from 1863 bp of mitochondrial DNA, 12 microsatellite loci, morphology and a correlative species distribution model. Our analyses reveal three genetically distinct groups with limited mitochondrial introgression in one group. All three groups exhibit distinct nuclear gene pools and distinct morphology. Two of these groups correspond to the previously recognized species Malayemys macrocephala (Chao Phraya Basin) and M. subtrijuga (Lower Mekong Basin). The third and genetically most divergent group from the Khorat Basin represents a previously unrecognized species, which is described herein. Although Malayemys are extensively traded and used for religious release, only few studied turtles appear to be translocated by humans. Historic fluctuations in potential distributions were assessed using species distribution models (SDMs). The Last Glacial Maximum (LGM) projection of the predictive SDMs suggests two distinct glacial distribution ranges, implying that the divergence of M. macrocephala and M. subtrijuga occurred in allopatry and was triggered by Pleistocene climate fluctuations. Only the projection derived from the global circulation model MIROC reveals a distinct third glacial distribution range for the newly discovered Malayemys species.

Malayemys khoratensis sp. nov.

Holotype: THNHM 25816, young, adult female (Fig 6) from Udon Thani, Udon Thani Province, Thailand (17.36555°N, 102.81427°E, WGS 1984), collected in July 2014 by FI and MC.

Fig 6. (A) Dorsal, (B) ventral, (C) lateral, and (D) frontal views of the holotype of Malayemys khoratensis (THNHM 25816, young, adult female from Udon Thani, Thailand).

Fig 7. Morphological differences in shell characteristics and head colouration patterns of Malayemys khoratensis (orange), Malayemys macrocephala (blue), Malayemys subtrijuga (green).

Diagnosis: Malayemys species with a straight carapace length below 20 cm and a tricarinate, blackish-brown carapace, and a blackish-brown head with distinct yellowish facial stripes. Malayemys khoratensis differs from M. macrocephala by the following characters: (1) first vertebral scute roughly square and not tapered posteriorly (V1W/V1L: 0.83±0.09 vs. 0.74±0.19 in females, 0.83±0.12 vs. 0.69±0.09 in males); (2) lower marginal scutes 8–12 with a pattern of diagonal to cone-shaped blackish brown blotches originating from the outer posterior corner vs. narrow blackish-brown bars at the posterior sutures; (3) infraorbital stripe not or rarely reaching the loreal seam, not broadened at the suture vs. always reaching the loreal seam and usually distinctly broadened at the suture; (4) infraorbital stripes only slightly curved below anterior edge of eyes vs. distinctly curved or angled; (5) short yellowish postocular stripe (between supraorbital and infraorbital stripe) lacking or reduced vs. postocular stripe always present and distinct (Fig 7).

Etymology: The species epithet refers to the Khorat Basin, the watershed to which the range of the new species appears to be restricted. The proposed English common name is Khorat Snail-eating Turtle.

Malayemys khoratensis (orange), Malayemys macrocephala (blue), Malayemys subtrijuga (green).

Distribution: M. khoratensis is so far only known from the Khorat Basin of northeastern Thailand. More precisely from Sikhio District, Nakhon Ratchasima Province, a location drained by the Mun River, and the provinces of Udon Thani (type locality) and Nong Bua Lamphu, in areas associated with the Chi River, a tributary of the Mun River.

Flora Ihlow, Melita Vamberger, Morris Flecks, Timo Hartmann, Michael Cota, Sunchai Makchai, Pratheep Meewattana, Jeffrey E. Dawson, Long Kheng, Dennis Rödder and Uwe Fritz. 2016. Integrative Taxonomy of Southeast Asian Snail-Eating Turtles (Geoemydidae: Malayemys) Reveals A New Species and Mitochondrial Introgression.
 PLoS ONE.  DOI: 10.1371/journal.pone.0153108