Phylogenomic datasets provide both precision and accuracy in estimating the timescale of placental mammal phylogeny

Proceedings of the Royal Society B: Biological Sciences - Tập 279 Số 1742 - Trang 3491-3500 - 2012
Mario dos Reis1, Jun Inoue2,1, Masami Hasegawa3, Robert J. Asher4, Philip C. J. Donoghue5, Ziheng Yang1
1Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London, UK
2Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Chiba, Japan
3School of Life Sciences, Fudan University, Handan Road no. 220, Shangai 200433, China
4Museum of Zoology, University of Cambridge, Downing Street, Cambridge, UK
5School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, UK

Tóm tắt

The fossil record suggests a rapid radiation of placental mammals following the Cretaceous–Paleogene (K–Pg) mass extinction 65 million years ago (Ma); nevertheless, molecular time estimates, while highly variable, are generally much older. Early molecular studies suffer from inadequate dating methods, reliance on the molecular clock, and simplistic and over-confident interpretations of the fossil record. More recent studies have used Bayesian dating methods that circumvent those issues, but the use of limited data has led to large estimation uncertainties, precluding a decisive conclusion on the timing of mammalian diversifications. Here we use a powerful Bayesian method to analyse 36 nuclear genomes and 274 mitochondrial genomes (20.6 million base pairs), combined with robust but flexible fossil calibrations. Our posterior time estimates suggest that marsupials diverged from eutherians 168–178 Ma, and crown Marsupialia diverged 64–84 Ma. Placentalia diverged 88–90 Ma, and present-day placental orders (except Primates and Xenarthra) originated in a ∼20 Myr window (45–65 Ma) after the K–Pg extinction. Therefore we reject a pre K–Pg model of placental ordinal diversification. We suggest other infamous instances of mismatch between molecular and palaeontological divergence time estimates will be resolved with this same approach.

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Proceedings of the Royal Society B: Biological Sciences

Tập 279 Số 1742

3491-3500

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