Monday, October 29, 2012

New squamate phylogeny

Epictia tenella. JCM
A new study, published online in Biology Letters on Sept. 19, has utilized a massive molecular dataset (161 squamate species for up to 44 nuclear genes each and 33 717 base pairs), the largest genetic datasets assembled for reptiles.to reconstruct the evolutionary history of lizards and snakes. The results reveal a surprising finding about the evolution of snakes: that most snakes we see living on the surface today arose from ancestors that lived underground.

The article, entitled "Resolving the phylogeny of lizards and snakes (Squamata) with extensive sampling of genes and species," describes research led by John J. Wiens, an Associate Professor in the Department of Ecology and Evolution at Stony Brook University.

In contrast to most other recent studies, the authors found that dibamids and gekkotans are together the sister group to all other squamates. The results also show that almost all groups of snakes arose from within a bizarre group of burrowing blind snakes called scolecophidians. This finding implies that snakes ancestrally lived underground, and that the thousands of snake species living today on the surface evolved from these subterranean ancestors. Remarkably, they found the distinctive scolecophidians (blind snakes) are paraphyletic with respect to other snakes, suggesting that snakes were primitively burrowers and subsequently re-invaded surface habitats.

The authors suggest that there are still traces of this subterranean ancestry in the anatomy of surface-dwelling snakes. "For example, no matter where they live, snakes have an elongate body and a relatively short tail, and outside of snakes, this body shape is only found in lizards that live underground," said Professor Wiens. "Snakes have kept this same basic body shape as they have evolved to invade nearly every habitat on the planet -- from rainforest canopies to deserts and even the oceans."

Citation
J. J. Wiens, C. R. Hutter, D. G. Mulcahy, B. P. Noonan, T. M. Townsend, J. W. Sites, T. W. Reeder. Resolving the phylogeny of lizards and snakes (Squamata) with extensive sampling of genes and species. 2012. Biology Letters, 2012; DOI: 10.1098/rsbl.2012.0703

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