THE RELATION BETWEEN THE NEUTRALITY INDEX FOR MITOCHONDRIAL GENES AND THE DISTRIBUTION OF MUTATIONAL EFFECTS ON FITNESS
Article first published online: 11 APR 2012
© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.
Volume 66, Issue 8, pages 2427–2438, August 2012
How to Cite
Betancourt, A. J., Blanco-Martin, B. and Charlesworth, B. (2012), THE RELATION BETWEEN THE NEUTRALITY INDEX FOR MITOCHONDRIAL GENES AND THE DISTRIBUTION OF MUTATIONAL EFFECTS ON FITNESS. Evolution, 66: 2427–2438. doi: 10.1111/j.1558-5646.2012.01628.x
- Issue published online: 26 JUL 2012
- Article first published online: 11 APR 2012
- Accepted manuscript online: 21 MAR 2012 09:21PM EST
- Received May 16, 2011 , Accepted February 18, 2012 , Data Archived: Dryad doi:10.5061/dryad.8bp5pp44
- Gamma distribution;
- log-normal distribution;
- mitochondrial genome;
- neutrality index;
- population genetics
We explore factors affecting patterns of polymorphism and divergence (as captured by the neutrality index) at mammalian mitochondrial loci. To do this, we develop a population genetic model that incorporates a fraction of neutral amino acid sites, mutational bias, and a probability distribution of selection coefficients against new nonsynonymous mutations. We confirm, by reanalyzing publicly available datasets, that the mitochondrial cyt-b gene shows a broad range of neutrality indices across mammalian taxa, and explore the biological factors that can explain this observation. We find that observed patterns of differences in the neutrality index, polymorphism, and divergence are not caused by differences in mutational bias. They can, however, be explained by a combination of a small fraction of neutral amino acid sites, weak selection acting on most amino acid mutations, and differences in effective population size among taxa.