Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, Karnataka, India.
Natural History Museum Berlin, Berlin, Germany.
Mol Biol Evol. 2017 Dec 1;34(12):3169-3175. doi: 10.1093/molbev/msx240.
Many experimental and field studies have shown that adaptation can occur very rapidly. Two qualitatively different modes of fast adaptation have been proposed: selective sweeps wherein large shifts in the allele frequencies occur at a few loci and evolution via small changes in the allele frequencies at many loci. Although the first process has been thoroughly investigated within the framework of population genetics, the latter is based on quantitative genetics and is much less understood. Here we summarize results from our recent theoretical studies of a quantitative genetic model of polygenic adaptation that makes explicit reference to population genetics to bridge the gap between the two frameworks. Our key results are that polygenic adaptation may be a rapid process and can proceed via subtle or dramatic changes in the allele frequency depending on the sizes of the phenotypic effects relative to a threshold value. We also discuss how the signals of polygenic selection may be detected in the genome. Although powerful methods are available to identify signatures of selective sweeps at loci controlling quantitative traits, the development of statistical tests for detecting small shifts of allele frequencies at quantitative trait loci is still in its infancy.
许多实验和实地研究表明，适应可以非常迅速地发生。已经提出了两种快速适应的定性不同模式：选择清扫，其中在少数几个基因座上发生等位基因频率的大转移，以及通过许多基因座上等位基因频率的微小变化进行进化。虽然第一个过程已经在群体遗传学的框架内进行了彻底的研究，但后者基于数量遗传学，理解得要少得多。在这里，我们总结了我们最近关于多基因适应的定量遗传模型的理论研究结果，该模型明确参考了群体遗传学，以弥合这两个框架之间的差距。我们的主要结果是，多基因适应可能是一个快速的过程，可以通过等位基因频率的微妙或剧烈变化来进行，具体取决于表型效应相对于阈值的大小。我们还讨论了如何在基因组中检测多基因选择的信号。虽然有强大的方法可用于识别控制数量性状的基因座上选择清扫的特征，但用于检测数量性状基因座上等位基因频率微小变化的统计测试的发展仍处于起步阶段。
