Evidência de evolução convergente molecular

quarta-feira, abril 29, 2009

Evidence for an ancient adaptive episode of convergent molecular evolution

Todd A. Castoea,1, A. P. Jason de Koninga,1, Hyun-Min Kima, Wanjun Gua,2, Brice P. Noonanb, Gavin Naylorc, Zhi J. Jiangd,e, Christopher L. Parkinsond,e, and David D. Pollocka,3

aDepartment of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045; bDepartment of Biology, University of Mississippi, Box 1848, University, MS 38677; cDepartment of Scientific Computing, Dirac Science Library, Florida State University, Tallahassee, FL 32306; dCenter for Computational Science, University of Miami, 1120 Northwest 14th Street, Miami, FL 33136; and eDepartment of Biology, University of Central Florida, 4000 Central Florida Boulevard, Orlando, FL 32816

Edited by David M. Hillis, University of Texas, Austin, TX, and approved March 20, 2009 (received for review January 9, 2009)


Documented cases of convergent molecular evolution due to selection are fairly unusual, and examples to date have involved only a few amino acid positions. However, because convergence mimics shared ancestry and is not accommodated by current phylogenetic methods, it can strongly mislead phylogenetic inference when it does occur. Here, we present a case of extensive convergent molecular evolution between snake and agamid lizard mitochondrial genomes that overcomes an otherwise strong phylogenetic signal. Evidence from morphology, nuclear genes, and most sites in the mitochondrial genome support one phylogenetic tree, but a subset of mostly amino acid-altering substitutions (primarily at the first and second codon positions) across multiple mitochondrial genes strongly supports a radically different phylogeny.

The relevant sites generally evolved slowly but converged between ancient lineages of snakes and agamids.We estimate that 44 of 113 predicted convergent changes distributed across all 13 mitochondrial protein-coding genes are expected to have arisen from nonneutral causes—a remarkably large number. Combined with strong previous evidence for adaptive evolution in snake mitochondrial proteins, it is likely that much of this convergent evolution was driven by adaptation. These results indicate that nonneutral convergent molecular evolution in mitochondria can
occur at a scale and intensity far beyond what has been documented previously, and they highlight the vulnerability of standard phylogenetic methods to the presence of nonneutral convergent sequence evolution.

Keywords adaptation convergence phylogenetics reptile


PDF gratuito do artigo aqui.