Data from: Post-glacial northward expansion and genetic differentiation between migratory and sedentary populations of the broad-tailed hummingbird (Selasphorus platycercus)

Unlike other migratory hummingbirds in North America, the broad-tailed hummingbird (Selasphorus platycercus) exhibits both long-distance migratory behaviour in the USA and sedentary behaviour in Mexico and Guatemala. We examined the evolution of migration linked to its northward expansion using a multi-perspective approach. We analysed variation in morphology, mitochondrial and nuclear DNA, estimated migration rates between migratory and sedentary populations, compared divergence times with the occurrence of Quaternary climate events, and constructed species distribution models to predict where migratory and sedentary populations resided during the Last Glacial Maximum (LGM) and Last Interglacial (LIG) events. Our results are consistent with a recent northward population expansion driven by migration from southern sedentary populations. Phylogeographical analyses and population genetics methods revealed that migratory populations in the USA and sedentary populations in Mexico of the platycercus subspecies form one admixed population, and that sedentary populations from southern Mexico and Guatemala (guatemalae) undertook independent evolutionary trajectories. Species distribution modelling revealed that the species is a niche tracker and that the climate conditions associated with modern obligate migrants in the USA were not present during the LIG, which provides indirect evidence for recent migratory behaviour in broad-tailed hummingbirds on the temporal scale of glacial cycles. The finding that platycercus hummingbirds form one genetic population and that suitable habitat for migratory populations was observed in eastern Mexico during the LIG also suggests that the conservation of overwintering sites is crucial for obligate migratory populations currently facing climate change effects.

与北美其他迁徙性蜂鸟不同，阔尾蜂鸟（Selasphorus platycercus）同时兼具两种行为模式：在美国境内表现为长距离迁徙行为，在墨西哥与危地马拉境内则为留居行为。本研究采用多视角研究方法，探究了与其种群北扩相关的迁徙演化机制。我们对其形态学特征、线粒体DNA（mitochondrial DNA）与核DNA（nuclear DNA）的变异情况进行了分析，估算了迁徙种群与留居种群间的迁徙速率，将分化时间与第四纪气候事件的发生时间进行比对，并构建了物种分布模型，以预测末次冰盛期（Last Glacial Maximum, LGM）与末次间冰期（Last Interglacial, LIG）期间迁徙种群与留居种群的潜在分布区域。本研究结果与“南部留居种群的迁徙行为推动了该物种近期的种群北扩”这一结论高度吻合。系统地理学分析与种群遗传学方法结果显示，platycercus亚种的美国境内迁徙种群与墨西哥境内留居种群共同构成一个混合种群；而墨西哥南部与危地马拉境内的guatemalae亚种留居种群则走上了独立的演化轨迹。物种分布模型结果表明，该物种属于生态位追踪者；美国境内现代专性迁徙种群所对应的气候条件在末次间冰期并未出现，这为阔尾蜂鸟在冰期周期尺度上出现近期迁徙行为提供了间接证据。研究还发现，platycercus蜂鸟构成一个遗传种群，且末次间冰期期间墨西哥东部存在迁徙种群的适宜栖息地；这一结果同时表明，对于当前正受气候变化影响的专性迁徙种群而言，越冬栖息地的保护至关重要。