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）可能会推动物种形成（speciation），因为差异化的配偶选择与配偶竞争可快速引发生殖隔离（reproductive isolation）。与之相对，性选择也可能延缓物种形成——多配偶制（polygamous）个体可通过提升繁殖扩散（breeding dispersal）能力来获得更多配偶。较高的繁殖扩散率会增强基因流（gene flow），进而降低多配偶物种种群的分化水平。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，验证多配偶制如何影响鸻形目鸟类的物种分化。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显著更弱，距离隔离效应（isolation-by-distance）也更不显著。与该结果一致的是，针对136种鸻形目鸟类的比较分析（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。与之形成对照的是，迁徙行为（migratory behaviour）既未对遗传分化产生显著预测效应，也未影响亚种丰富度。综合来看，本研究结果表明，与多配偶制相关的扩散行为可促进基因流、限制种群分化。因此，正如多配偶制物种所经历的强烈性选择，在鸻形目鸟类中可能会成为物种形成的“制动器”，而非“助推引擎”。我们还讨论了对该研究结果的其他可能解释，并呼吁开展更多相关研究，以厘清性选择、扩散行为与物种分化之间的内在关联。