Department of Botany and Biodiversity Research, Faculty of Life Sciences, University of Vienna, Vienna, Austria.
Institute of Science and Technology Austria, Klosterneuburg, Austria.
Mol Ecol. 2019 Apr;28(7):1579-1581. doi: 10.1111/mec.15048. Epub 2019 Apr 9.
One of the most striking and consistent results in speciation genomics is the heterogeneous divergence observed across the genomes of closely related species. This pattern was initially attributed to different levels of gene exchange-with divergence preserved at loci generating a barrier to gene flow but homogenized at unlinked neutral loci. Although there is evidence to support this model, it is now recognized that interpreting patterns of divergence across genomes is not so straightforward. One problem is that heterogenous divergence between populations can also be generated by other processes (e.g. recurrent selective sweeps or background selection) without any involvement of differential gene flow. Thus, integrated studies that identify which loci are likely subject to divergent selection are required to shed light on the interplay between selection and gene flow during the early phases of speciation. In this issue of Molecular Ecology, Rifkin et al. () confront this challenge using a pair of sister morning glory species. They wisely design their sampling to take the geographic context of individuals into account, including geographically isolated (allopatric) and co-occurring (sympatric) populations. This enabled them to show that individuals are phenotypically less differentiated in sympatry. They also found that the loci that resist introgression are enriched for those most differentiated in allopatry and loci that exhibit signals of divergent selection. One great strength of the study is the combination of methods from population genetics and molecular evolution, including the development of a model to simultaneously infer admixture proportions and selfing rates.
在物种形成基因组学中，最引人注目且始终一致的结果之一是，在密切相关的物种的基因组中观察到的异质分歧。这种模式最初归因于基因交换的不同水平——在产生基因流动障碍的基因座上，分歧得以保留，但在不相关的中性基因座上则趋于同质化。尽管有证据支持该模型，但现在人们认识到，解释基因组间分歧的模式并不那么简单。一个问题是，种群之间的异质分歧也可以由其他过程（例如，反复的选择清扫或背景选择）产生，而无需涉及差异基因流动。因此，需要进行综合研究来确定哪些基因座可能受到分歧选择的影响，以便揭示在物种形成的早期阶段选择和基因流动之间的相互作用。在本期《分子生态学》中，Rifkin 等人 () 使用一对姐妹朝颜属物种来应对这一挑战。他们明智地设计了他们的采样，考虑了个体的地理背景，包括地理隔离（异域）和共存（同域）种群。这使他们能够表明，同域共存的个体在表型上的分化程度较低。他们还发现，抵制基因渗入的基因座富集了在异域中分化程度最高的基因座和表现出分歧选择信号的基因座。该研究的一个巨大优势是将种群遗传学和分子进化的方法结合在一起，包括开发一种同时推断混合比例和自交率的模型。
