Data from: Persistent inter- and intraspecific gene exchange within a parallel radiation of caterpillar hunter beetles (Calosoma sp.) from the Galápagos

When environmental gradients are repeated on different islands within an archipelago, similar selection pressures may act within each island, resulting in the repeated occurrence of ecologically similar species on each island. The evolution of ecotypes within such radiations may either result from dispersal, that is each ecotype evolved once and dispersed to different islands where it colonized its habitat, or through repeated and parallel speciation within each island. However, it remains poorly understood how gene flow during the divergence process may shape such patterns. In the Galápagos islands, three phenotypically similar species of the beetle genus Calosoma occur at higher elevations of different islands, while lowlands are occupied by a fourth species. By genotyping all major populations within this radiation for two nuclear and three mitochondrial gene fragments and seven microsatellite markers, we found strong support that the oldest divergence separates the highland species of the oldest island from the remaining species. Despite their morphological distinctness, highland species of the remaining islands were genetically closely related to the lowland population on each island and within the same magnitude as lowland populations sampled at different islands. Repeated evolution of highland ecotypes out of the lowland species appears the most likely scenario and estimates of geneflow rates revealed extensive admixture among ecotypes within islands, as well as between islands. These findings indicate that gene exchange among the different populations and species may have shaped the phylogenetic relationships and the repeated evolution of these ecotypes.当群岛内不同岛屿上的环境梯度呈重复分布时，各岛屿内部可能承受相似的选择压力，进而促使各岛屿上反复涌现生态特征相似的物种。此类适应辐射类群中的生态型演化，可通过两种途径实现：其一为扩散作用，即每种生态型仅经历一次演化事件，随后扩散至不同岛屿并定居于对应栖息地；其二为各岛屿内部独立发生的平行物种形成。但目前学界对分化过程中的基因流如何塑造此类演化格局仍缺乏深入认知。在加拉帕戈斯群岛（Galápagos Islands），不同岛屿的高海拔区域均分布有3种形态相似的步甲属（Calosoma）物种，而低海拔区域则由第4个物种占据。本研究对该辐射类群的所有主要种群开展基因分型分析，检测了2个核基因片段、3个线粒体基因片段以及7个微卫星标记（microsatellite markers）。结果显示，最古老的分化事件将最古老岛屿的高海拔物种与其余物种分离开来，该结论得到了强有力的支持。尽管其余岛屿的高海拔物种在形态上具有显著分化，但它们在遗传层面与各自岛屿的低地种群亲缘关系紧密，且遗传分化程度与不同岛屿间的低地种群处于同一量级。由此可见，由低地物种种群反复演化出高海拔生态型是可能性最大的演化路径。对基因流速率的估算结果表明，各岛屿内部不同生态型之间，以及不同岛屿之间均存在广泛的遗传混合。本研究的发现揭示，不同种群与物种间的基因交换，可能塑造了这些类群的系统发育关系以及生态型的重复演化过程。