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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Clonal interference in large populations
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Clonal interference in large populations

机译：大量人群的克隆干扰

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摘要

Clonal interference, the competition between lineages arising from different beneficial mutations in an asexually reproducing population, is an important factor determining the tempo and mode of microbial adaptation. The standard theory of this phenomenon neglects the occurrence of multiple mutations as well as the correlation between loss by genetic drift and clonal competition, which is questionable in large populations. Working within the Wright-Fisher model with multiplicative fitness (no epistasis), we determine the rate of adaptation asymptotically for very large population sizes and show that the standard theory fails in this regime. Our study also explains the success of the standard theory in predicting the rate of adaptation for moderately large populations. Furthermore, we show that the nature of the substitution process changes qualitatively when multiple mutations are allowed for, because several mutations can be fixed in a single fixation event. As a consequence, the index of dispersion for counts of the fixation process displays a minimum as a function of population size, whereas the origination process of fixed mutations becomes completely regular for very large populations. We find that the number of mutations fixed in a single event is geometrically distributed as in the neutral case. These conclusions are based on extensive simulations combined with analytic results for the limit of infinite population size.
机译：无性繁殖种群中不同有益突变产生的谱系之间的竞争是克隆干扰，是决定微生物适应的速度和方式的重要因素。这种现象的标准理论忽略了多个突变的发生以及遗传漂移造成的损失与克隆竞争之间的相关性，这在许多人群中是值得怀疑的。在具有可乘适应性（无上位性）的Wright-Fisher模型中，我们渐近确定了非常大的人口规模的适应率，并表明标准理论在这种情况下是失败的。我们的研究还解释了标准理论在预测中等规模人口适应率方面的成功。此外，我们表明当允许多个突变时，替换过程的性质会发生质的变化，因为可以在单个固定事件中固定多个突变。结果，固定过程计数的分散指数显示出最小的种群数量函数，而固定突变的起源过程对于非常大的种群变得完全规则。我们发现在单个事件中固定的突变数与中性情况一样在几何上分布。这些结论是基于广泛的模拟与分析结果相结合得出的，即无穷人口规模的局限性。

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