Data from: Pleistocene speciation with and without gene flow in Euphaea damselflies of subtropical and tropical East Asian islands

Climatic oscillations during the Pleistocene period could have had a profound impact on the origin of tropical species by the alternation of allopatric isolation and inter-population gene flow cycles. However, whether tropical speciation involves strictly allopatric isolation, or proceeds in the face of homogenizing gene flow, is relatively unclear. Here, we investigated geographical modes of speciation in four closely-related Euphaea damselfly species endemic to the subtropical and tropical East Asian islands using coalescent analyses of a multi-locus data set. The reconstructed phylogenies demonstrated distinct species status for each of the four species and the existence of two sister species pairs, E. formosa/E. yayeyamana and E. decorata/E. ornata. The species divergence time of the sibling Euphaea damselflies dates back to within the last one Mya of the Middle to Lower Pleistocene. The speciation between the populous E. formosa of Taiwan and the less numerous E. yayeyamana of the Yaeyama islands occurred despite significant bidirectional, asymmetric gene flow, which is strongly inconsistent with a strictly allopatric model. In contrast, speciation of the approximately equal-sized populations of E. decorata of the south-east Asian mainland and E. ornata of Hainan is inferred to have involved allopatric divergence without gene flow. Our findings suggest that differential selection of natural or sexual environments is a prominent driver of species divergence in subtropical E. formosa and E. yayeyamana; whereas for tropical E. decorata and E. ornata at lower latitudes, allopatric isolation may well be a pivotal promoter of species formation.

更新世（Pleistocene）气候波动可通过异域隔离与种群间基因流循环的交替过程，对热带物种的起源产生深远影响。然而，热带物种形成究竟是严格依赖异域隔离，还是可在同质化基因流的作用下发生，目前仍相对模糊。本研究针对东亚亚热带与热带岛屿特有的4种近缘色蟌属（Euphaea）豆娘物种，利用多位点数据集的溯祖分析，探究了其物种形成的地理模式。重建的系统发育树证实了该4个物种各自独立的物种地位，并发现存在两对姐妹种：台湾色蟌（E. formosa）/八重山色蟌（E. yayeyamana），以及华丽色蟌（E. decorata）/装饰色蟌（E. ornata）。该两对近缘色蟌的物种分化时间均可追溯至更新世中晚期至早更新世的100万年以内。尽管台湾种群规模庞大的台湾色蟌与八重山群岛种群稀少的八重山色蟌之间的物种形成过程伴随显著的双向不对称基因流，但该结果与严格异域隔离模型强烈相悖。与之相反，东南亚大陆的华丽色蟌与海南岛的装饰色蟌种群规模大致相当，其物种形成过程被推断为无基因流的异域分化。本研究结果显示，对于亚热带的台湾色蟌与八重山色蟌而言，自然与性选择环境的差异化选择是物种分化的重要驱动因素；而对于纬度更低的热带类群华丽色蟌与装饰色蟌来说，异域隔离或许是物种形成的关键促进因子。