Data from: The tempo of trait divergence in geographic isolation: avian speciation across the Marañon valley of Peru

Geographic isolation is considered essential to most speciation events, but our understanding of what controls the pace and degree of phenotypic divergence among allopatric populations remains poor. Why do some taxa exhibit phenotypic differentiation across barriers to dispersal, whereas others do not? To test factors controlling phenotypic divergence in allopatry, we employed a comparative phylogeographic approach consisting of replicates of ecologically similar Andean bird species isolated across a major biogeographic barrier, the Marañon valley of Peru. Our study design leverages variation among co-distributed taxa in their degree of plumage, morphometric and vocal differentiation across the Marañon to examine the tempo of phenotypic evolution. We found that substantial plumage differences between populations required roughly two million years to evolve. In contrast, morphometric trait evolution showed greater idiosyncrasy and stasis. Our results demonstrate that despite a large degree of idiosyncrasy in the relationship between genetic and phenotypic divergence across taxa and environments, comparative studies within regions may reveal predictability in the pace of phenotypic divergence. Our results also suggest that social selection is important for driving differentiation of populations found in similar environments.

地理隔离被认为是多数物种形成事件的核心前提，但我们对调控异域种群（allopatric populations）间表型分化的速率与程度的机制仍不甚明晰。为何部分类群在扩散障碍两侧呈现表型分化，而其余类群却无此现象？为探究调控异域表型分化的各类驱动因素，本研究采用比较系统地理学（comparative phylogeography）方法，选取多组生态相似的安第斯鸟类类群，这些类群均被秘鲁马农河谷这一重要生物地理屏障所隔离。本研究设计利用同分布类群在马农河谷两侧的羽色、形态计量学特征及鸣声分化程度的差异，以解析表型演化的速率。研究发现，种群间显著的羽色分化大约需要200万年的演化时间方可形成。与之形成对比的是，形态计量学特征的演化则表现出更强的类群特异性与演化停滞性。本研究结果表明，尽管不同类群与环境下遗传分化与表型分化间的关联存在极强的特异性，但区域内的比较研究仍可揭示表型分化速率的可预测性。此外，本研究结果还暗示，社会选择（social selection）对于驱动相似环境下种群的分化具有重要作用。