Testing the neutral theory of molecular evolution with genomic data from Drosophila
Testing the neutral theory of molecular evolution with genomic data from Drosophila
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DOI：
10.1038/4151024a
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发表时间：
2002-02-28
期刊：
影响因子：
64.8
通讯作者：
Wu, CI
中科院分区：
文献类型：
--
作者：
Fay, JC;Wyckoff, GJ;Wu, CI
虽然在许多基因中发现了正选择，但其对蛋白质进化的总体贡献是有争议的（1）。如果大部分分子进化是中性的，那么氨基酸（A）多态性与同义（S）多态性的比率平均应该等于分歧（2）。比较黑腹果蝇多态性的A/S比与模拟果蝇的分歧表明，分歧的A/S比是两倍高，这一差异通常归因于正选择。但是，由于有效种群规模的增加而导致的选择约束的增加也可以解释这一观察结果，如果是这样的话，所有基因都应该受到类似的影响。在这里，我们表明多态性和分歧之间的差异仅限于一小部分基因，这些基因也进化得更快，这意味着正选择是负责任的。在其他物种中也观察到了比多态性更高的A/S比率，这表明适应性进化的速率远远高于分子进化的中性理论所允许的。
Although positive selection has been detected in many genes, its overall contribution to protein evolution is debatable(1). If the bulk of molecular evolution is neutral, then the ratio of amino-acid (A) to synonymous (S) polymorphism should, on average, equal that of divergence(2). A comparison of the A/S ratio of polymorphism in Drosophila melanogaster with that of divergence from Drosophila simulans shows that the A/S ratio of divergence is twice as high-a difference that is often attributed to positive selection. But an increase in selective constraint owing to an increase in effective population size could also explain this observation, and, if so, all genes should be affected similarly. Here we show that the difference between polymorphism and divergence is limited to only a fraction of the genes, which are also evolving more rapidly, and this implies that positive selection is responsible. A higher A/S ratio of divergence than of polymorphism is also observed in other species, which suggests a rate of adaptive evolution that is far higher than permitted by the neutral theory of molecular evolution.