Stephan Wolfgang
Leibniz-Institute for Evolution and Biodiversity Science Natural History Museum Berlin Germany.
Ecol Evol. 2021 Oct 27;11(22):15896-15904. doi: 10.1002/ece3.8259. eCollection 2021 Nov.
Detecting selective sweeps driven by strong positive selection and localizing the targets of selection in the genome play a major role in modern population genetics and genomics. Most of these analyses are based on the classical model of genetic hitchhiking proposed by Maynard Smith and Haigh (1974, , 23, 23). Here, we consider extensions of the classical two-locus model. Introducing mutation at the strongly selected site, we analyze the conditions under which soft sweeps may arise. We identify a new parameter (the ratio of the beneficial mutation rate to the selection coefficient) that characterizes the occurrence of multiple-origin soft sweeps. Furthermore, we quantify the hitchhiking effect when the polymorphism at the linked locus is not neutral but maintained in a mutation-selection balance. In this case, we find a smaller relative reduction of heterozygosity at the linked site than for a neutral polymorphism. In our analysis, we use a semi-deterministic approach; i.e., we analyze the frequency process of the beneficial allele in an infinitely large population when its frequency is above a certain threshold; however, for very small frequencies in the initial phase after the onset of selection we rely on diffusion theory.
在现代群体遗传学和基因组学中，检测由强正向选择驱动的选择性清除以及定位基因组中的选择目标起着重要作用。这些分析大多基于梅纳德·史密斯和黑格（1974年，第23卷，第23期）提出的经典遗传搭便车模型。在此，我们考虑经典双位点模型的扩展。在强选择位点引入突变后，我们分析了可能出现软清除的条件。我们确定了一个新参数（有益突变率与选择系数的比率），该参数表征了多起源软清除的发生情况。此外，当连锁位点的多态性不是中性的而是在突变 - 选择平衡中维持时，我们对遗传搭便车效应进行了量化。在这种情况下，我们发现连锁位点杂合度的相对降低幅度比中性多态性时要小。在我们的分析中，我们使用了一种半确定性方法；即，当有益等位基因频率高于某个阈值时，我们分析其在无限大群体中的频率变化过程；然而，对于选择开始后初始阶段非常小的频率，我们依赖扩散理论。
