Institut für Populationsgenetik, Vetmeduni, Vienna, Austria.
Genome Biol Evol. 2020 Jun 1;12(6):890-904. doi: 10.1093/gbe/evaa073.
In molecular population genetics, adaptation is typically thought to occur via selective sweeps, where targets of selection have independent effects on the phenotype and rise to fixation, whereas in quantitative genetics, many loci contribute to the phenotype and subtle frequency changes occur at many loci during polygenic adaptation. The sweep model makes specific predictions about frequency changes of beneficial alleles and many test statistics have been developed to detect such selection signatures. Despite polygenic adaptation is probably the prevalent mode of adaptation, because of the traditional focus on the phenotype, we are lacking a solid understanding of the similarities and differences of selection signatures under the two models. Recent theoretical and empirical studies have shown that both selective sweep and polygenic adaptation models could result in a sweep-like genomic signature; therefore, additional criteria are needed to distinguish the two models. With replicated populations and time series data, experimental evolution studies have the potential to identify the underlying model of adaptation. Using the framework of experimental evolution, we performed computer simulations to study the pattern of selected alleles for two models: 1) adaptation of a trait via independent beneficial mutations that are conditioned for fixation, that is, selective sweep model and 2) trait optimum model (polygenic adaptation), that is adaptation of a quantitative trait under stabilizing selection after a sudden shift in trait optimum. We identify several distinct patterns of selective sweep and trait optimum models in populations of different sizes. These features could provide the foundation for development of quantitative approaches to differentiate the two models.
在分子群体遗传学中，适应性通常被认为是通过选择清除发生的，其中选择的目标对表型有独立的影响，并上升到固定，而在数量遗传学中，许多基因座对表型有贡献，并且在多基因适应过程中许多基因座的频率发生细微变化。清除模型对有益等位基因的频率变化做出了具体的预测，并且已经开发了许多测试统计量来检测这种选择特征。尽管多基因适应可能是普遍的适应模式，但由于传统上关注表型，我们对两种模型下选择特征的相似性和差异缺乏深入的了解。最近的理论和实证研究表明，选择性清除和多基因适应模型都可能导致类似清除的基因组特征；因此，需要额外的标准来区分这两种模型。利用复制的种群和时间序列数据，实验进化研究有可能确定适应的潜在模型。使用实验进化的框架，我们进行了计算机模拟，以研究两种模型的选择等位基因模式：1）通过条件固定的独立有利突变来适应特征，即选择性清除模型和 2）特征最优模型（多基因适应），即在特征最优突然变化后，对数量特征进行稳定选择的适应。我们在不同大小的种群中确定了几种不同的选择清除和特征最优模型的模式。这些特征可以为开发区分这两种模型的定量方法提供基础。
