Genetic hitchhiking and the dynamic buildup of genomic divergence during speciation with gene flow

A major issue in evolutionary biology is explaining patterns of differentiation observed in population genomic data, as divergence can be due to both direct selection on a locus and genetic hitchhiking. “Divergence hitchhiking” (DH) theory postulates that divergent selection on a locus reduces gene flow at physically linked sites, facilitating the formation of localized clusters of tightly linked, diverged loci. “Genome hitchhiking” (GH) theory emphasizes genome-wide effects of divergent selection. Past theoretical investigations of DH and GH focused on static snapshots of divergence. Here, we used simulations assessing a variety of strengths of selection, migration rates, population sizes, and mutation rates to investigate the relative importance of direct selection, GH, and DH in facilitating the dynamic buildup of genomic divergence as speciation proceeds through time. When divergently selected mutations were limiting, GH promoted divergence, but DH had little measurable effect. When...

进化生物学中的一个核心议题是解释群体基因组数据中观测到的分化模式，因为种群分化既可源于单个位点上的直接选择，也可由遗传搭车（genetic hitchhiking）效应引发。“分化搭车（divergence hitchhiking, DH）”理论假定，某一位点的趋异选择会降低与其物理连锁的位点间的基因流，进而促进紧密连锁的分化位点形成局部集群。“基因组搭车（genome hitchhiking, GH）”理论则着重强调趋异选择在全基因组范围内的效应。过往针对DH与GH的理论研究多聚焦于分化的静态快照。本研究通过模拟实验，系统调控选择强度、迁移率、种群规模与突变率等参数，探究在物种形成随时间推进的过程中，直接选择、GH与DH在推动基因组分化动态积累过程中的相对重要性。当趋异选择突变较为稀缺时，GH可促进基因组分化，而DH几乎未产生可检测到的效应。当...