Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC, United States of America.
Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, Chapel Hill, NC, United States of America.
PLoS One. 2023 May 16;18(5):e0285129. doi: 10.1371/journal.pone.0285129. eCollection 2023.
Host individuals are commonly coinfected with multiple parasite species that may interact to shape within-host parasite community structure. In addition to within-host species interactions, parasite communities may also be structured by other processes like dispersal and ecological drift. The timing of dispersal (in particular, the temporal sequence in which parasite species infect a host individual) can alter within-host species interactions, setting the stage for historical contingency by priority effects, but how persistently such effects drive the trajectory of parasite community assembly is unclear, particularly under continued dispersal and ecological drift. We tested the role of species interactions under continued dispersal and ecological drift by simultaneously inoculating individual plants of tall fescue with a factorial combination of three symbionts (two foliar fungal parasites and a mutualistic endophyte), then deploying the plants in the field and tracking parasite communities as they assembled within host individuals. In the field, hosts were exposed to continued dispersal from a common pool of parasites, which should promote convergence in the structure of within-host parasite communities. Yet, analysis of parasite community trajectories found no signal of convergence. Instead, parasite community trajectories generally diverged from each other, and the magnitude of divergence depended on the initial composition of symbionts within each host, indicating historical contingency. Early in assembly, parasite communities also showed evidence of drift, revealing another source of among-host divergence in parasite community structure. Overall, these results show that both historical contingency and ecological drift contributed to divergence in parasite community assembly within hosts.
宿主个体通常会同时感染多种寄生虫物种，这些寄生虫可能会相互作用，从而影响宿主内寄生虫群落的结构。除了宿主内物种相互作用外，寄生虫群落的结构还可能受到其他过程的影响，如扩散和生态漂变。扩散的时间（特别是寄生虫物种感染宿主个体的时间顺序）会改变宿主内物种相互作用，为优先效应下的历史偶然性创造条件，但这些效应持续驱动寄生虫群落组装轨迹的方式尚不清楚，特别是在持续的扩散和生态漂变下。我们通过同时向高羊茅个体接种三种共生体（两种叶部真菌寄生虫和一种互利共生内生真菌）的因子组合，测试了在持续扩散和生态漂变下物种相互作用的作用，然后将这些植物部署在野外，并跟踪寄生虫群落在宿主个体内的组装情况。在野外，宿主会受到来自共同寄生虫库的持续扩散的影响，这应该会促进宿主内寄生虫群落结构的趋同。然而，对寄生虫群落轨迹的分析没有发现趋同的信号。相反，寄生虫群落轨迹通常彼此发散，发散的幅度取决于每个宿主内共生体的初始组成，这表明存在历史偶然性。在组装的早期，寄生虫群落也显示出漂变的证据，这揭示了寄生虫群落结构中宿主间发散的另一个来源。总的来说，这些结果表明，历史偶然性和生态漂变都导致了宿主内寄生虫群落组装的发散。
