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）时期的气候波动，通过异域隔离（allopatric isolation）与种群间基因流循环的交替，可能对热带物种的起源产生了深远影响。然而，热带物种成种究竟是严格依赖异域隔离，还是在同质化基因流（homogenizing gene flow）的存在下仍能完成，目前仍相对不明晰。本研究针对分布于亚热带及热带东亚岛屿的4个近缘色蟌属（Euphaea）豆娘物种，利用多位点数据集（multi-locus data set）的溯祖分析（coalescent analyses），探究了其成种的地理模式。重建的系统发育树（phylogenies）显示，这4个物种各自均具有明确的物种地位，且存在两对姐妹种对：E. formosa/E. yayeyamana与E. decorata/E. ornata。这些近缘色蟌属豆娘的物种分化时间可追溯至更新世中-早阶段的距今100万年（Mya）以内。台湾种群数量庞大的E. formosa与八重山群岛种群稀少的E. yayeyamana之间的成种过程，尽管存在显著的双向不对称基因流，却仍得以完成，这一结果与严格的异域成种模型完全相悖。与之相反，东南亚大陆的E. decorata与海南岛的E. ornata的种群规模大致相当，其成种过程被推断为无基因流的异域分化过程。本研究结果表明，自然与性选择环境的差异化选择，是亚热带类群E. formosa与E. yayeyamana物种分化的重要驱动力；而对于低纬度的热带类群E. decorata与E. ornata而言，异域隔离或许是物种形成的关键推动因素。