Data from: Polygamy slows down population divergence in shorebirds

Sexual selection may act as a promotor of speciation since divergent mate choice and competition for mates can rapidly lead to reproductive isolation. Alternatively, sexual selection may also retard speciation since polygamous individuals can access additional mates by increased breeding dispersal. High breeding dispersal should hence increase gene flow and reduce diversification in polygamous species. Here we test how polygamy predicts diversification in shorebirds using genetic differentiation and subspecies richness as proxies for population divergence. Examining microsatellite data from 79 populations in ten plover species (Genus: Charadrius) we found that polygamous species display significantly less genetic structure and weaker isolation-by-distance effects than monogamous species. Consistent with this result, a comparative analysis including 136 shorebird species showed significantly fewer subspecies for polygamous than for monogamous species. By contrast, migratory behaviour neither predicted genetic differentiation nor subspecies richness. Taken together, our results suggest that dispersal associated with polygamy may facilitate gene flow and limit population divergence. Therefore, intense sexual selection, as occurs in polygamous species, may act as a brake rather than an engine of speciation in shorebirds. We discuss alternative explanations for these results and call for further studies to understand the relationships between sexual selection, dispersal and diversification.

性选择（Sexual selection）或可作为物种形成（speciation）的促进因子，因为差异化配偶选择与配偶竞争可快速引发生殖隔离（reproductive isolation）。反之，性选择也可能延缓物种形成：多配偶制（polygamy）个体可通过提升繁殖扩散（breeding dispersal）来获取更多配偶，而高繁殖扩散水平会增加基因流（gene flow），进而降低多配偶物种种群的多样化水平。
本研究以遗传分化（genetic differentiation）和亚种丰富度（subspecies richness）作为种群分化（population divergence）的替代指标，检验多配偶制对滨鸟（shorebirds）多样化进程的预测能力。我们对10种鸻属（Charadrius）鸟类的79个种群的微卫星（microsatellite）数据进行分析后发现，相较于单配偶制物种，多配偶制物种的遗传结构（genetic structure）显著更弱，距离隔离（isolation-by-distance）效应也更弱。
与此结果一致，针对136种滨鸟的比较分析（comparative analysis）显示，多配偶制物种的亚种数量显著少于单配偶制物种。与之形成对比的是，迁徙行为（migratory behaviour）既无法预测遗传分化水平，也无法预测亚种丰富度。
综合来看，本研究结果表明，与多配偶制相关的扩散行为可能会促进基因流、限制种群分化。因此，多配偶制物种所经历的强烈性选择，在滨鸟中可能是物种形成的"刹车"而非"引擎"。我们还讨论了对该结果的其他潜在解释，并呼吁开展更多研究以阐明性选择、扩散与多样化之间的关联。