1 Savannah River Ecology Laboratory, University of Georgia , Aiken, SC , USA.
2 Warnell School of Forestry and Natural Resources, University of Georgia , Athens, GA 30602 , USA.
Proc Biol Sci. 2019 Jun 12;286(1904):20190439. doi: 10.1098/rspb.2019.0439. Epub 2019 Jun 5.
Understanding why some parasites emerge in novel host communities while others do not has broad implications for human and wildlife health. In the case of haemosporidian blood parasites, epidemic wild bird mortalities on oceanic islands have been linked to Plasmodium spp., but not genera like Haemoproteus. Indeed, Haemoproteus is absent from many oceanic islands. By contrast, birds on continental islands share long coevolutionary histories with both Plasmodium and Haemoproteus, and are thus ideal model systems to elucidate eco-evolutionary endpoints associated with these parasites in oceanic islands. Here, we examine eco-evolutionary dynamics of avian haemosporidian in the Shola sky-island archipelago of the Western Ghats, India. Our analyses reveal that compared to Plasmodium, Haemoproteus lineages were highly host-specific and diversified via co-speciation with their hosts. We show that community structure of host-generalist Plasmodium was primarily driven by geographical factors (e.g. biogeographic barriers), while that of host-specialist Haemoproteus was driven by host species barriers (e.g. phylogenetic distance). Consequently, a few host species can harbour a high diversity of Plasmodium lineages which, in turn, are capable of infecting multiple host species. These two mechanisms can act in concert to increase the risk of introduction, establishment, and emergence of novel Plasmodium lineages in island systems.
了解为什么有些寄生虫会出现在新的宿主群落中，而有些则不会，这对人类和野生动物的健康都有广泛的影响。就血液寄生虫疟原虫而言，海洋岛屿上的野生鸟类大规模死亡与疟原虫有关，但与血孢子虫属等寄生虫无关。事实上，血孢子虫属在许多海洋岛屿上都不存在。相比之下，大陆岛屿上的鸟类与疟原虫和血孢子虫属都有着长期的共同进化历史，因此是阐明与这些寄生虫在海洋岛屿上相关的生态进化终点的理想模型系统。在这里，我们研究了印度西高止山脉的 Shola 天空岛屿群岛中鸟类血液寄生虫的生态进化动态。我们的分析表明，与疟原虫相比，血孢子虫谱系具有高度的宿主特异性，并通过与宿主的共同进化而多样化。我们表明，宿主泛化的疟原虫群落结构主要受地理因素（如生物地理屏障）驱动，而宿主特化的血孢子虫群落结构则受宿主物种屏障（如系统发育距离）驱动。因此，少数宿主物种可以容纳多种疟原虫谱系的高度多样性，而这些疟原虫谱系又能够感染多种宿主物种。这两种机制可以协同作用，增加新型疟原虫谱系在岛屿系统中引入、建立和出现的风险。
