Dispersal and the transition to sympatry in vertebrates

Under allopatric speciation models, a key step in the build-up of species richness is population dispersal leading to the co-occurrence of previously geographically isolated forms. Despite its central importance for community assembly, the extent to which the transition from spatial segregation (allopatry or parapatry) to coexistence (sympatry) is a predictable process, or alternatively one governed by chance and the vagaries of biogeographic history, remains poorly understood. Here, we use estimated divergence times and current patterns of geographical range overlap among sister species to explore the evolution of sympatry in vertebrates. We show that rates of transition to sympatry vary predictably according to ecology, being faster in marine or strongly dispersive terrestrial clades. This association with organism vagility is robust to the relative frequency of geographical speciation modes and consistent across taxonomic scales and metrics of dispersal ability. These findings reject...在异域物种形成（allopatric speciation）模型中，物种丰富度积累的核心环节是种群扩散，借此可使此前地理隔离的类群实现共存。尽管该过程对群落组装具有核心重要性，但从空间隔离（异域分布（allopatry）或邻域分布（parapatry））到物种共存（同域分布（sympatry））的转变究竟属于可预测的过程，还是由偶然性与生物地理历史的多变性所主导，目前仍不甚明晰。本研究借助估算得到的分化时间与姊妹物种间当前的地理分布重叠格局，探究脊椎动物的同域分布演化规律。研究结果表明，向同域分布的转变速率可依据生态特征进行预测：海洋类群或扩散能力较强的陆生演化支的转变速率更快。这种与生物扩散能力相关的关联不受地理成种模式相对频率的影响，且在不同分类学尺度以及各类扩散能力度量标准下均保持稳定。上述研究结果驳斥了