Data from: Genetic coupling of female mate choice with polygenic ecological divergence facilitates stickleback speciation

<b>Abstract</b><br/>Ecological speciation with gene flow is widespread in nature, but it presents a conundrum: how are associations between traits under divergent natural selection and traits that contribute to assortative mating maintained? Theoretical models suggest that genetic mechanisms inhibiting free recombination between loci underlying these two types of traits (hereafter, “genetic coupling”) can facilitate speciation. Here, we perform a direct test for genetic coupling by mapping both divergent traits and female mate choice in a classic model of ecological speciation: sympatric benthic and limnetic threespine stickleback (Gasterosteus aculeatus). By measuring mate choice in F2 hybrid females, we allowed for recombination between loci underlying assortative mating and those under divergent ecological selection. In semi-natural mating arenas in which females had access to both benthic and limnetic males, we found that F2 females mated with males similar to themselves in body size and shape. In addition, we found two quantitative trait loci (QTLs) associated with female mate choice that also predicted female morphology along the benthic-limnetic trait axis. Furthermore, a polygenic genetic model that explains adaptation to contrasting benthic and limnetic feeding niches also predicted F2 female mate choice. Together, these results provide empirical evidence that genetic coupling of assortative mating with traits under divergent ecological selection helps maintain species in the face of gene flow, despite a polygenic basis for adaptation to divergent environments.

**摘要**
存在基因流的生态物种形成在自然界中广泛分布，但该过程存在一个核心未解难题：受趋异自然选择作用的性状，与助力选型交配（assortative mating）的性状之间的关联是如何得以维持的？理论模型表明，能够抑制这两类性状对应基因座间自由重组的遗传机制（下文简称「遗传耦合（genetic coupling）」），可有效推动物种形成进程。本研究以生态物种形成的经典模型——同域底栖与浮游三刺鱼（*Gasterosteus aculeatus*）为研究对象，通过对趋异性状与雌性配偶选择进行定位分析，直接检验了遗传耦合效应。我们通过测定F₂杂交雌性个体的配偶选择，使得调控选型交配的基因座与受趋异生态选择作用的基因座之间能够发生重组。在雌性可同时接触底栖与浮游雄性的半自然交配竞技场中，我们发现F₂雌性个体倾向于与自身体型和形态相似的雄性交配。此外，我们鉴定到两个与雌性配偶选择相关的数量性状位点（quantitative trait loci, QTLs），这些位点同时可预测雌性在底栖-浮游性状轴上的形态特征。进一步分析显示，一个能够解释对底栖与浮游摄食生态位趋异适应的多基因遗传模型，同样可以预测F₂雌性的配偶选择。综上，本研究结果提供了直接实验证据：尽管对趋异环境的适应基于多基因基础，但选型交配与受趋异生态选择作用的性状之间的遗传耦合，能够在基因流存在的情况下维持物种的独立性。