The relation between the neutrality index for mitochondrial genes and the distribution of mutational effects on fitness

Andrea Betancourt, Bernardo Blanco-Martin, Brian Charlesworth

Research output: Contribution to journalArticlepeer-review

Abstract

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 data sets, 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.
Original languageEnglish
Pages (from-to)2427-2438
Number of pages11
JournalEvolution
Volume66
Issue number8
Early online date11 Apr 2012
DOIs
Publication statusPublished - 30 Aug 2012

Keywords

  • Gamma distribution
  • log-normal distribution
  • mitochondrial genome
  • neutrality index
  • population genetics

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