Whether adaptation is limited by the beneficial mutation supply is a long-standing question of evolutionary genetics, which is more generally related to the determination of the adaptive substitution rate and its relationship with species effective population size (Ne) and genetic diversity. Empirical evidence reported so far is equivocal, with some but not all studies supporting a higher adaptive substitution rate in large-Ne than in small-Ne species. We gathered coding sequence polymorphism data and estimated the adaptive amino-acid substitution rate ωa, in 50 species from ten distant groups of animals with markedly different population mutation rate θ. We reveal the existence of a complex, timescale dependent relationship between species adaptive substitution rate and genetic diversity. We find a positive relationship between ωa and θ among closely related species, indicating that adaptation is indeed limited by the mutation supply, but this was only true in relatively low-θ taxa. In contrast, we uncover no significant correlation between ωa and θ at a larger taxonomic scale, suggesting that the proportion of beneficial mutations scales negatively with species' long-term Ne.

中文翻译：

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适应受到突变的限制吗？遗传多样性对动物适应性替代率的时标依赖性影响。

适应性是否受到有益突变供应的限制是进化遗传学的一个长期存在的问题，这更普遍地与确定适应性替代率及其与物种有效种群大小（Ne）和遗传多样性的关系有关。迄今为止报道的经验证据是模棱两可的，一些但并非全部研究都支持大Ne中的适应性替代率高于小Ne中的适应性替代率。我们收集了编码序列多态性数据，并估计了十个远处动物群体中的50种动物的自适应氨基酸取代率ωa，它们的种群突变率θ明显不同。我们揭示了物种适应性替代率和遗传多样性之间存在复杂的，与时间尺度有关的关系。我们在密切相关的物种中发现ωa和θ之间存在正相关，这表明适应性确实受突变供给的限制，但这仅在θ相对较低的分类群中才成立。相反，在较大的分类尺度上，我们没有发现ωa与θ之间没有显着相关性，这表明有益突变的比例与物种的长期Ne呈负比例。