Department of Life Science & Center for Tropical Ecology and Biodiversity, Tunghai University, Taichung 40704, Taiwan.
Mol Ecol. 2012 Aug;21(15):3739-56. doi: 10.1111/j.1365-294X.2012.05654.x. Epub 2012 May 31.
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 interpopulation 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 multilocus data set. The reconstructed phylogenies demonstrated distinct species status for each of the four species and the existence of two sister species pairs, Euphaea 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 southeast 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.
更新世期间的气候振荡可能通过异地隔离和种群间基因流循环的交替，对热带物种的起源产生深远影响。然而，热带物种形成是否涉及严格的异地隔离，或者在基因流同质化的情况下进行，相对来说还不清楚。在这里，我们使用多基因数据集的合并分析，调查了东亚亚热带和热带岛屿特有、四个密切相关的 Euphaea 蜻蜓物种的地理物种形成模式。重建的系统发育表明，这四个物种中的每一个都具有独特的物种地位，并且存在两个姐妹种对，Euphaea formosa/E. yayeyamana 和 E. decorata/E. ornata。姐妹 Euphaea 蜻蜓的物种分化时间回溯到中更新世到下更新世的最后 100 万年。尽管存在双向、不对称的基因流，但人口众多的台湾 E. formosa 和人口较少的琉球群岛的 E. yayeyamana 之间的物种形成是发生了的，这与严格的异地隔离模式强烈不一致。相比之下，东南亚大陆的近似大小种群 E. decorata 和海南岛的 E. ornata 的物种形成被推断为涉及没有基因流的异地分歧。我们的研究结果表明，自然或性环境的差异选择是亚热带 E. formosa 和 E. yayeyamana 物种分化的主要驱动因素；而对于热带的 E. decorata 和 E. ornata 来说，在较低的纬度，异地隔离可能是物种形成的关键促进因素。
