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...宿主-寄生虫相互作用极易受到其他物种通过性状介导产生的强烈间接效应影响。然而，这类间接效应是否能够跨越土壤边界，并连接空间上隔离的生物体，目前仍未得到探索。本研究表明，丛枝菌根真菌（arbuscular mycorrhizal fungi, AMF）可通过改变宿主植物（马利筋属Asclepias sp.）的性状，显著影响草食动物——君主斑蝶Danaus plexippus与其原生动物寄生虫Ophryocystis elektroscirrha之间的相互作用，该互作涉及四个生物界的物种交互。在本实验中，AMF可影响寄生虫的毒力、宿主的抗病性以及宿主对寄生虫的耐受力。上述效应同时取决于AMF的接种密度与马利筋的物种种类：对于部分马利筋物种而言，AMF会间接提高取食该植物的君主斑蝶的染病程度；而对于另一些马利筋物种，AMF则会缓解君主斑蝶的染病状况。这种物种特异性主要由AMF对植物初生代谢（磷元素）以及……