Global patterns of diversification in the history of modern amphibians

doi:10.1073/pnas.0608378104

Global patterns of diversification in the history of modern amphibians

*Unit of Ecology and Systematics, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium;
^†Department of Zoology, Natural History Museum, London SW7 5BD, United Kingdom; and
^‡Centre for Environmental Management of Degraded Ecosystems, School of Environmental Studies, University of Delhi, Delhi 110007, India

Edited by Francisco J. Ayala, University of California, Irvine, CA, and approved November 21, 2006 (received for review September 22, 2006)

Abstract

The fossil record of modern amphibians (frogs, salamanders, and caecilians) provides no evidence for major extinction or radiation episodes throughout most of the Mesozoic and early Tertiary. However, long-term gradual diversification is difficult to reconcile with the sensitivity of present-day amphibian faunas to rapid ecological changes and the incidence of similar environmental perturbations in the past that have been associated with high turnover rates in other land vertebrates. To provide a comprehensive overview of the history of amphibian diversification, we constructed a phylogenetic timetree based on a multigene data set of 3.75 kb for 171 species. Our analyses reveal several episodes of accelerated amphibian diversification, which do not fit models of gradual lineage accumulation. Global turning points in the phylogenetic and ecological diversification occurred after the end-Permian mass extinction and in the late Cretaceous. Fluctuations in amphibian diversification show strong temporal correlation with turnover rates in amniotes and the rise of angiosperm-dominated forests. Approximately 86% of modern frog species and >81% of salamander species descended from only five ancestral lineages that produced major radiations in the late Cretaceous and early Tertiary. This proportionally late accumulation of extant lineage diversity contrasts with the long evolutionary history of amphibians but is in line with the Tertiary increase in fossil abundance toward the present.

Footnotes

^§To whom correspondence should be addressed. E-mail: fbossuyt{at}vub.ac.be
Author contributions: K.R., D.J.G., M.W., S.P.L., S.D.B., and F.B. designed research; K.R., K.G., L.M., and F.B. performed research; K.R., D.J.G., M.W., S.P.L., S.D.B., and F.B. contributed new reagents/analytic tools; K.R. and S.D.B. analyzed data; and K.R., D.J.G., M.W., S.P.L., S.D.B., K.G., L.M., and F.B. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS direct submission.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. AY948743–AY948944, EF107160–EF107500, and EFl10994–EFl10998).
This article contains supporting information online at www.pnas.org/cgi/content/full/0608378104/DC1.
Abbreviations:

LTT,

lineage-through-time;

ML,

maximum likelihood;

Mya,

million years ago;

Myr,

million years;

PL,

penalized likelihood;

RTT,

rate-through-time.