Data from: Joint effects of habitat, zooplankton, host stage structure and diversity on amphibian chytrid

Why does the severity of parasite infection differ dramatically across
habitats? This question remains challenging to answer because multiple
correlated pathways drive disease. Here, we examined habitat–disease links
through direct effects on parasites and indirect effects on parasite
predators (zooplankton), host diversity and key life stages of hosts. We
used a case study of amphibian hosts and the chytrid fungus,
Batrachochytrium dendrobatidis, in a set of permanent and ephemeral alpine
ponds. A field experiment showed that ultraviolet radiation (UVR) killed
the free-living infectious stage of the parasite. Yet, permanent ponds
with more UVR exposure had higher infection prevalence. Two
habitat-related indirect effects worked together to counteract parasite
losses from UVR: (i) UVR reduced the density of parasite predators and
(ii) permanent sites fostered multi-season host larvae that fuelled
parasite production. Host diversity was unlinked to hydroperiod or UVR but
counteracted parasite gains; sites with higher diversity of host species
had lower prevalence of infection. Thus, while habitat structure explained
considerable variation in infection prevalence through two indirect
pathways, it could not account for everything. This study demonstrates the
importance of creating mechanistic, food web-based links between multiple
habitat dimensions and disease.

为何寄生虫感染的严重程度在不同栖息地间存在巨大差异？这一问题的解答仍具挑战性，因为疾病由多种相互关联的路径驱动。在此，我们通过对寄生虫的直接影响，以及对寄生虫捕食者（浮游动物，zooplankton）、宿主多样性和宿主关键生活史阶段的间接影响，探究了栖息地与疾病之间的关联。我们以一组永久性和临时性高山池塘中的两栖类宿主及壶菌（chytrid fungus）——蛙壶菌（Batrachochytrium dendrobatidis）为研究案例。野外实验表明，紫外线辐射（UVR）能杀死该寄生虫的自由生活感染阶段。然而，暴露于更多UVR的永久性池塘，其感染患病率（prevalence）更高。两种与栖息地相关的间接效应共同作用，抵消了UVR导致的寄生虫损失：（i）UVR降低了寄生虫捕食者的密度；（ii）永久性栖息地培育了跨季节的宿主幼虫，为寄生虫繁殖提供了动力。宿主多样性与水文周期（hydroperiod）或UVR无关，但能抵消寄生虫的增殖；宿主物种多样性更高的栖息地，其感染患病率更低。因此，尽管栖息地结构通过两条间接路径解释了感染患病率的显著变异，但它无法解释所有现象。本研究证明了在多维度栖息地与疾病之间建立基于食物网的机制性关联的重要性。