Departments of Biology and Entomology, University of Maryland, College Park, MD 20742, USA.
Philos Trans R Soc Lond B Biol Sci. 2012 Feb 5;367(1587):451-60. doi: 10.1098/rstb.2011.0260.
In allopatric populations, geographical separation simultaneously isolates the entire genome, allowing genetic divergence to accumulate virtually anywhere in the genome. In sympatric populations, however, the strong divergent selection required to overcome migration produces a genetic mosaic of divergent and non-divergent genomic regions. In some recent genome scans, each divergent genomic region has been interpreted as an independent incidence of migration/selection balance, such that the reduction of gene exchange is restricted to a few kilobases around each divergently selected gene. I propose an alternative mechanism, 'divergence hitchhiking' (DH), in which divergent selection can reduce gene exchange for several megabases around a gene under strong divergent selection. Not all genes/markers within a DH region are divergently selected, yet the entire region is protected to some degree from gene exchange, permitting genetic divergence from mechanisms other than divergent selection to accumulate secondarily. After contrasting DH and multilocus migration/selection balance (MM/SB), I outline a model in which genomic isolation at a given genomic location is jointly determined by DH and genome-wide effects of the progressive reduction in realized migration, then illustrate DH using data from several pairs of incipient species in the wild.
在异域种群中，地理隔离同时隔离了整个基因组，使得遗传分化几乎可以在基因组的任何地方积累。然而，在同域种群中，为了克服迁移而需要的强烈的分歧选择会产生分歧和非分歧基因组区域的遗传镶嵌。在最近的一些基因组扫描中，每个分歧的基因组区域都被解释为迁移/选择平衡的独立事件，使得基因交换的减少仅限于每个分歧选择基因周围的几个千碱基。我提出了一种替代机制，即“分歧搭便车”（DH），在这种机制中，强烈的分歧选择可以减少几个兆碱基范围内的基因交换。DH 区域内并非所有基因/标记都受到分歧选择，但整个区域在某种程度上受到基因交换的保护，从而允许除分歧选择以外的机制积累次要的遗传分化。在对比了 DH 和多基因迁移/选择平衡（MM/SB）之后，我概述了一个模型，其中特定基因组位置的基因组隔离是由 DH 和实现的迁移减少的全基因组效应共同决定的，然后使用来自野生近缘物种的几个对的数据来说明 DH。
