Genetic drift is an important evolutionary force of strength inversely proportional to N _e , the effective population size. The impact of drift on genome diversity and evolution is known to vary among species, but quantifying this effect is a difficult task. Here we assess the magnitude of variation in drift power among species of animals via its effect on the mutation load - which implies also inferring the distribution of fitness effects of deleterious mutations (DFE). To this aim, we analyze the non-synonymous (amino-acid changing) and synonymous (amino-acid conservative) allele frequency spectra in a large sample of metazoan species, with a focus on the primates vs. fruit flies contrast. We show that a Gamma model of the DFE is not suitable due to strong differences in estimated shape parameters among taxa, while adding a class of lethal mutations essentially solves the problem. Using the Gamma + lethal model and assuming that the mean deleterious effects of non-synonymous mutations is shared among species, we estimate that the power of drift varies by a factor of at least 500 between large-N _e and small-N _e species of animals, i.e., an order of magnitude more than the among-species variation in genetic diversity. Our results are relevant to Lewontin's paradox while further questioning the meaning of the N _e parameter in population genomics.

中文翻译：

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不同物种间 Ne 的差异有多大？


遗传漂变是一种重要的进化力量_，其强度与有效种群规模Ne成反比。众所周知，漂移对基因组多样性和进化的影响因物种而异，但量化这种影响是一项艰巨的任务。在这里，我们通过其对突变负荷的影响来评估动物物种之间漂移能力的变化幅度——这也意味着推断有害突变（DFE）的适应度效应的分布。为此，我们分析了大量后生动物物种中的非同义（氨基酸变化）和同义（氨基酸保守）等位基因频谱，重点关注灵长类动物与果蝇的对比。我们表明，由于类群之间估计形状参数的巨大差异，DFE 的 Gamma 模型并不适用，而添加一类致死突变基本上可以解决该问题。使用 Gamma + 致死模型并假设非同义突变的平均有害影响在物种之间共享，我们估计大N _e和小N _e物种之间的漂移能力至少相差 500 倍。动物之间的差异，即遗传多样性的差异比物种间差异大一个数量级。我们的结果与 Lewontin 悖论相关，同时进一步质疑N _e参数在群体基因组学中的含义。