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

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.

本研究旨在探究影响哺乳类动物线粒体位点多态性与分化模式（以中性指数（Neutrality Index）表征）的相关因素。为此，我们构建了一套群体遗传学模型，该模型纳入了中性氨基酸位点占比、突变偏倚，以及针对新发非同义突变的选择系数概率分布。我们通过重新分析公开可用的数据集证实：哺乳类类群中线粒体细胞色素b（cyt-b）基因的中性指数分布跨度广泛；并对可解释该观测结果的生物学因素展开了系统性探究。研究发现，观测到的中性指数、多态性与分化模式差异并非由突变偏倚差异所导致。但该现象可通过以下因素的组合得到合理解释：中性氨基酸位点占比极低、多数氨基酸突变受弱选择作用，以及不同类群间有效种群规模存在差异。