Within-island diversification in a passerine bird

The presence of congeneric taxa on the same island suggests the possibility of in situ divergence, but can also result from multiple colonizations of previously diverged lineages. Here, using genome-wide data from a large population sample, we test the hypothesis that intra-island divergence explains the occurrence of four geographic forms meeting at hybrid zones in the Reunion grey white-eye (Zosterops borbonicus), a species complex endemic to the small volcanic island of Reunion. Using population genomic and phylogenetic analyses, we reconstructed the population history of the different forms. We confirmed the monophyly of the complex and found that one of the lowland forms is paraphyletic and basal relative to others, a pattern highly consistent with in situ divergence. Our results suggest initial colonization of the island through the lowlands, followed by expansion into the highlands, which led to the evolution of a distinct geographical form, genetically and ecologically different...同一岛屿上共存同属类群，既暗示了原地分化（in situ divergence）的可能性，也可能源自已分化支系的多次定殖事件。本研究借助大种群样本的全基因组数据（genome-wide data），以分布于留尼旺这座小型火山岛的特有物种复合群——留尼旺绣眼鸟（Zosterops borbonicus）为研究对象，检验了“岛内分化可解释四种地理型在杂交带相遇”这一假说。通过种群基因组学（population genomic）与系统发育分析，我们重建了不同地理型的种群历史。研究确认了该物种复合群的单系性（monophyly），并发现其中一种低地类群为并系群（paraphyletic），且相对于其余类群处于系统发育基部，这一模式与原地分化假说高度契合。本研究结果显示，该类群最初通过低地完成岛屿定殖，随后向高地扩张并演化出一种独特的地理型，该类群在遗传与生态层面均存在差异……