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THE RELATION BETWEEN THE NEUTRALITY INDEX FOR MITOCHONDRIAL GENES AND THE DISTRIBUTION OF MUTATIONAL EFFECTS ON FITNESS
Author(s) -
Betancourt Andrea J.,
BlancoMartin Bernardo,
Charlesworth Brian
Publication year - 2012
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.2012.01628.x
Subject(s) - biology , nonsynonymous substitution , genetics , neutrality , neutral theory of molecular evolution , evolutionary biology , population , divergence (linguistics) , gene , genome , philosophy , linguistics , demography , epistemology , sociology
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.