Data from: Disease ecology across soil boundaries: effects of below-ground fungi on above-ground host–parasite interactions

Host–parasite interactions are subject to strong trait-mediated indirect
effects from other species. However, it remains unexplored whether such
indirect effects may occur across soil boundaries and connect spatially
isolated organisms. Here, we demonstrate that, by changing plant (milkweed
Asclepias sp.) traits, arbuscular mycorrhizal fungi (AMF) significantly
affect interactions between a herbivore (the monarch butterfly Danaus
plexippus) and its protozoan parasite (Ophryocystis elektroscirrha), which
represents an interaction across four biological kingdoms. In our
experiment, AMF affected parasite virulence, host resistance and host
tolerance to the parasite. These effects were dependent on both the
density of AMF and the identity of milkweed species: AMF indirectly
increased disease in monarchs reared on some species, while alleviating
disease in monarchs reared on other species. The species-specificity was
driven largely by the effects of AMF on both plant primary (phosphorus)
and secondary (cardenolides; toxins in milkweeds) traits. Our study
demonstrates that trait-mediated indirect effects in disease ecology are
extensive, such that below-ground interactions between AMF and plant roots
can alter host–parasite interactions above ground. In general, soil biota
may play an underappreciated role in the ecology of many terrestrial
host–parasite systems.

宿主-寄生虫互作（Host–parasite interactions）极易受到其他物种介导的性状间接效应影响。然而，此类间接效应是否可跨越土壤边界并连接空间隔离的生物，目前仍未得到探索。本研究证实，丛枝菌根真菌（arbuscular mycorrhizal fungi，AMF）可通过改变马利筋属（Asclepias sp.）植物的性状，显著影响植食性动物黑脉金斑蝶（Danaus plexippus）与其原生动物寄生虫奥菲奥囊虫（Ophryocystis elektroscirrha）之间的互作——这一互作跨越了四个生物界。在本实验中，AMF可影响寄生虫毒力、宿主抗性以及宿主对寄生虫的耐受性。此类效应同时依赖于AMF的密度与马利筋的物种种类：AMF可间接加重取食部分马利筋物种的黑脉金斑蝶的病害程度，却能减轻取食其他马利筋物种的黑脉金斑蝶的病害。这种物种特异性主要由AMF对植物初级性状（磷相关）与次级性状（强心苷——马利筋中的毒素）的调控作用所驱动。本研究表明，疾病生态学中由性状介导的间接效应分布广泛，即AMF与植物根系之间的地下互作可改变地上的宿主-寄生虫互作。总体而言，土壤生物群落在多数陆生宿主-寄生虫系统的生态学过程中可能扮演了长期被低估的角色。