Long-distance dispersal of pigeons and dove generated new ecological opportunities for host-switching and adaptive radiation by their parasites.

Adaptive radiation is an important mechanism of organismal diversification, and can be triggered by new ecological opportunities. Although poorly studied in this regard, parasites are an ideal group in which to study adaptive radiations because of their close associations with host species. Both experimental and comparative studies suggest that the ectoparasitic wing lice of pigeons and doves have adaptively radiated, leading to differences in body size and overall coloration. Here we show that long-distance dispersal by dove hosts was central to parasite diversification because it provided new ecological opportunities for parasites to speciate after host-switching. We further show that these new opportunities for host-switching decreased over time, with cospeciation becoming the more dominant mode of parasite speciation. Taken together, our results suggest that host dispersal, followed by host-switching, provided novel ecological opportunities that facilitated adaptive radiation by parasites.

适应辐射（Adaptive radiation）是有机体多样性分化的重要机制，可由全新的生态机遇所触发。尽管在该研究方向上的探索尚不充分，但寄生虫因其与宿主物种的紧密联系，成为探究适应辐射的理想类群。实验研究与比较研究均表明，鸽与鸠的外寄生羽虱（ectoparasitic wing lice）已发生适应性辐射，进而形成了体型与整体体色的分化。本研究证实，鸠类宿主的长距离扩散是寄生虫物种形成（speciation）的核心驱动因素：其为经历宿主转换（host-switching）的寄生虫提供了新的生态机遇，助力其完成物种形成过程。本研究进一步发现，这类宿主转换的新机遇随时间推移逐渐减少，共成种（cospeciation）逐渐成为寄生虫物种形成的主导模式。综合以上研究结果，本研究表明，宿主扩散继而引发宿主转换，为寄生虫的适应辐射提供了全新的生态机遇，从而推动了其适应性辐射进程。