Saturday, January 18, 2014

A new framework for studying blindsnakes, a previously underestimated snake diversity


Amerotyphlops cf. brongersmianus

The five families of sclecophoidians are the oldest group of extant snakes with an ancestor some place in the Jurassic. One family (Xenotyphlopidae) is monotypic and restricted to Madagascar, one family (Anomalepididae) is found only in the Neotropics, One is restricted to Southeast Asia and New Guinea (Gerrhopilidae), a fourth (Leptotyphlopidae)has the rather odd distribution of  Africa, southwestern Asia, Socotra Island,  the southwestern United States southward to Argentina; and they are present on many  Caribbean islands.  But, Typhlopidae is almost pan tropical and the largest family with 257 described species.

Scolecophidians are not just of interest for the evolutionary novelty of their specialized diet of social insects and associated adaptations. Because they are the most ancient (deeply-branching) group of living snakes  their relationships can be used to track plate tectonics  better than any other vertebrate group.

In a new paper published in Caribbean Herpetology, S. Blair Hedges, Angela Marion, Kelly  Lipp, Julie Marin, and Nicolas Vidal provide a taxonomic framework for typhlopid snakes of the Caribbean  as well as other regions of the planet.

Molecular data reveal large numbers of undescribed species, inferring that the true species diversity of these snakes is greatly underestimated.

The authors complied three separate molecular datasets expanding the worldwide scol­ecophidian dataset, called here dataset A; an Australian typhlopid dataset, dataset B  and an expanded West Indian typhlopid dataset, dataset C. The authors use new morphological data and 489 new DNA sequences, and propose a new taxonomic framework for the family Typhlopidae. Of 257 named species of typhlopid snakes, 92 are now represented in molecular phylogenies along with 60 additional species yet to be described.

The Afrotyphlopinae subfamily is distributed almost exclusively in sub-Saharan Africa and contains three genera: Afrotyphlops, Letheobia, and  Rhinotyphlops. The Asiatyphlopinae subfamily distributed in Asia, Australasia, and islands of the western and southern Pacific, and includes ten genera:  Acutotyphlops, Anilios,  Asiatyphlops gen. nov., Cyclotyphlops, Grypotyphlops, Indotyphlops  gen. nov., Malayotyphlops  gen. nov., Ramphotyphlops, Sundatyphlops  gen. nov., and  Xerotyphlops  gen. nov. The Madatyphlopinae subfamily  occurs only in Madagascar and includes one genus: Madatyphlops  gen. nov. The subfamily Typhlopinae occurs in the New World and includes four genera:  Amerotyphlops  gen. nov., Antillotyphlops  gen. nov., Cubatyphlops  gen. nov., and Typhlops.

The authors note that the most common theme encountered in studying the evolution of these snakes is their close association with geography. Their occurrence on islands never connected to continents demonstrates they are capable of dispersing (rafting) over deep water, and at the same time their relationships track plate tectonics better than any other vertebrate group. Species have unusually small distributions, and many species may be known from a single locality, and sympatric species sometimes have no distinguishing scale counts. Thus many unsubscribed species have been discovered using molecular data. All of this makes them an intriguing group to study, for understanding biogeography, ecology, behavior, and speciation. The entire article can be found on-line.

Citation
Hedges SB, Marion AB, Lipp KM, Marin J, Vidal N. 2014. A taxonomic framework for typhlopid snakes from the Caribbean and other regions (Reptilia, Squamata). Caribbean Herpetology  49:1–61

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