Tuesday, August 2, 2011

Amphibian Phylogeny Revised

Siren intermedia. JCM
Pyron and Weins have a new amphibian phylogeny that is now available on-line, prior to publication. No previous amphibian phylogeny used more than 522 species. However, other studies used limited taxon sampling and generated large numbers of partially overlapping sequence data for many species. The authors combine these data and produce a novel estimate of extant amphibian phylogeny, based on 2871 species (about 40% of living species) from 432 genera (85% of the 500 living genera). Species sampled averaged 2563 bp per species. The data set provides strong support for many groups recognized in previous studies, but it also suggests non-monophyly for several currently recognized families, particularly in hyloid frogs (e.g., Ceratophryidae, Cycloramphidae, Leptodactylidae, Strabomantidae). To correct these the authors provide a revised classification of extant amphibians for taxa traditionally delimited at the family and subfamily levels. The new phylogeny includes several new families, strongly supported by their data, but not recognized in current classifications (e.g., Alsodidae, Batrachylidae, Rhinodermatidae, Odontophrynidae, Telmatobiidae). Some highlights include the following. Within caecilians their results agree with other recent studies in supporting clades corresponding to Rhinatrematidae, Ichthyophiidae, and Caeciliidae, but the traditional family-level classification of caecilians that is used by Amphibia Web, (2011) was not supported by this study and they found the caeciliid subfamily Typhlonectinae to be paraphyletic. Within salamanders, the family and subfamily-level relationships were found to be  mostly consistent with most recent model-based molecular analyses and current classifications availabe on Amphibia Web and at Amphibian Species of the World web sites. However, they found strong support for a sister-group relationship between Sirenidae and all salamanders exclusive of Cryptobranchidae and Hynobiidae. Within frogs, the Hyloidea are several families were found not to be monophyletic: Ceratophryidae, Cycloramphidae, Leptodactylidae, and their solution is to recognizing several additional families relative to current classifications (Alsodidae, Batrachylidae, Odontophrynidae, Rhinodermatidae, Telmatobiidae) and synonymizing one (Strabomantidae with Craugastoridae). These newly recognized families are either re-definitions of previously recognized families (Rhinodermatidae,Telmatobiidae), or elevation of existing taxa presently below family rank (Alsodinae, Batrachylinae, Odontophrynini) to the rank of families. The study also provides evidence that the supermatrix approach provides an effective strategy for inferring large-scale phylogenies using the combined results of previous studies, despite many taxa having extensive missing data.

R. Alexander Pyron and John J. Wiens   2011. (in press) A large-scale phylogeny of Amphibia including over 2800 species, and a revised classification of extant frogs, salamanders, and caecilians. Molecular Phylogenetics and Evolution doi:10.1016/j.ympev.2011.06.012.

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