Sunday, June 23, 2013

Molecular phylogeny of a possibly extinct snake

Coluber cursor Lacépède, 1789, was described from Martinique and has been placed in the genera Herpetodryas, Dromicus, and Liophis  at various points in time. But molecular work suggests the snake is one of 41 species in the now greatly expanded genus Erythrolamprus. Erythrolamprus cursor.  Jowers and colleagues (2013) failed to find the snake in a search of its last known islet, Dianond Rock, literally a large rock about 5.8 hectares, 2 km off the coast of Martinique. Diamond Rock was the source of the last two specimens collected in 1964. Left with no alternative to sort out the snake's phylogenetic relationships, the authors extracted DNA from old museum specimens. They found  a sister relationship between E. cursor and E. juliae (another Antillean species known from Dominica, Guadeloupe, and Mairie-Galante). All sequences recovered had the same haplotype and the level of divergence between E. cursor and E. juliae, from the nearby island of Dominica, was lower than between other intraspecific distances within other Erythrolamprus. Furthermore, phylogenetic analyses confirm that these two species are sister taxa and share most recent common ancestry an estimated 2 million years ago. Diamond Rock lacks a frog population, and while E. cursor's close relatives seem to feed mostly on anurans, the Black Rock population must have been feeding on something else. There are four species of lizards living on the islet, and they seem to be likely prey, given that related species occasionally take lizards as well as frogs. The authors emphasize the urgent need to conduct an exhaustive survey on the supposed last population of E. cursor at Diamond Rock to establish the survival of this species there, and to understand how it may have adapted to such an ecosystem, especially in the sympatry of several introduced rodent species.

Citation
Jowers MJ, Caut S, Garcia-Mudarra JL, Alasaad S, Ineich I. 2013. Molecular Phylogenetics of the Possibly Extinct Martinique Ground Snake. Herpetologica 69: 227-236.

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