Data from: Gene trees, species trees and Earth history combine to shed light on the evolution of migration in a model avian system

The evolution of migration in birds has fascinated biologists for centuries. In this study, we performed phylogenetic-based analyses of Catharus thrushes, a model genus in the study of avian migration, and their close relatives. For these analyses, we used both mitochondrial and nuclear genes, and the resulting phylogenies were used to trace migratory traits and biogeographic patterns. Our results provide the first robust assessment of relationships within Catharus and relatives and indicate that both mitochondrial and autosomal genes contribute to overall support of the phylogeny. Measures of phylogenetic informativeness indicated that mitochondrial genes provided more signal within Catharus than did nuclear genes, whereas nuclear loci provided more signal for relationships between Catharus and close relatives than did mitochondrial genes. Insertion and deletion events also contributed important support across the phylogeny. Across all taxa included in the study, and for Catharus, possession of long-distance migration is reconstructed as the ancestral condition, and a North American (north of Mexico) ancestral area is inferred. Within Catharus, sedentary behaviour evolved after the first speciation event in the genus and is geographically and temporally correlated with Central American distributions and the final closure of the Central American Seaway. Migratory behaviour subsequently evolved twice in Catharus and is geographically and temporally correlated with a recolonization of North America in the late Pleistocene. By temporally linking speciation events with changes in migratory condition and events in Earth history, we are able to show support for several competing hypotheses relating to the geographic origin of migration.

数个世纪以来，鸟类迁徙的演化历程始终令生物学家心驰神往。本研究针对鸟类迁徙研究的模式类群——凯瑟鸫属（Catharus）鸫类（Catharus thrushes）及其近缘类群，开展了基于系统发育的分析。本次分析同时采用了线粒体基因（mitochondrial genes）与核基因（nuclear genes），所得系统发育树被用于追溯迁徙性状与生物地理格局的演化轨迹。本研究结果首次对凯瑟鸫属及其近缘类群的系统发育关系给出了稳健评估，结果显示线粒体基因与常染色体基因（autosomal genes）均为系统发育树的整体支持度提供了重要贡献。系统发育信息性测算表明，在凯瑟鸫属内部，线粒体基因提供的系统发育信号强于核基因；而在凯瑟鸫属与其近缘类群的系统发育关系分析中，核基因座（nuclear loci）提供的信号则优于线粒体基因。插入缺失事件同样为整个系统发育树提供了关键支持依据。针对本研究涵盖的所有类群以及凯瑟鸫属本身，长距离迁徙均被重建为祖先性状，且其祖先分布区被推断为北美（墨西哥以北区域）。在凯瑟鸫属内，留居习性这一性状是在该属首次物种形成事件之后演化而来的，其地理与时间分布格局均与中美洲分布区以及中美洲海道（Central American Seaway）的最终闭合事件存在相关性。随后，凯瑟鸫属内的迁徙习性又独立演化了两次，其地理与时间分布均与更新世晚期（late Pleistocene）重新殖民北美大陆的事件相关联。通过将物种形成事件与迁徙性状变化以及地球历史事件进行时间维度上的关联，本研究为若干与迁徙地理起源相关的竞争性假说提供了支持证据。