Parasite‐driven cascades or hydra effects: Susceptibility and foraging depression shape parasite–host–resource interactions
Parasite‐driven cascades or hydra effects: Susceptibility and foraging depression shape parasite–host–resource interactions
复制标题
寄生虫驱动的级联或水螅效应：易感性和觅食抑郁症形成寄生虫-宿主-资源相互作用
DOI：
10.1111/1365-2435.14030
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发表时间：
2022
影响因子：
5.2
通讯作者：
Hall, Spencer Ryan
中科院分区：
文献类型：
--
作者：
Walsman, Jason Cosens;Strauss, Alexander Thomas;Hall, Spencer Ryan
寄生虫杀死宿主，但也可以间接地增加其资源的丰度。根据这些资源反馈，寄生虫会在多大程度上降低宿主密度？它们能增加宿主密度吗？为了寻找答案，我们整合了性状测量、资源-宿主-寄生虫模型和浮游生物实验流行病。这一组合揭示了寄生虫如何降低或增加宿主密度。这一系列结果反映了寄生虫驱动的死亡率（密度介导的效应）和与寄生虫繁殖体接触后的觅食抑制（性状介导的效应）之间的紧张关系。在该模型中，当对感染的易感性增加感染流行率时，死亡率上升。这些大规模流行病在抑制宿主的同时释放资源（形成营养级联）。相反，当寄主不那么敏感，寄生虫抑制寄主觅食时，资源反馈可以在流行病期间提高寄主密度（产生水螅效应），特别是在资源承载能力较高的情况下。这种组合产生了水螅效应，因为它提高了相对于每个宿主资源消耗的初级产量（宿主密度的两个关键决定因素）。我们通过性状测量和中观实验对这些预测进行了定性测试。浮游动物寄主的无性系在觅食抑制和敏感性方面存在差异。然后，利用这些不同的宿主基因型，我们在提供低营养或高营养（以操纵承载能力）的中生态系统中制造流行病。水螅效应和营养级联在模型预测的性状-营养组合中都出现了。因此，我们展示了寄生虫的性状和密度介导效应之间的紧张关系如何在流行病期间控制宿主密度的命运——从营养级联到水螅效应。在《华尔街日报》博客上阅读免费的《简明语言摘要》。
Parasites kill hosts but also can indirectly increase the abundance of their resources. Given this resource feedback, how much will parasites decrease host density? Can they increase host density? Seeking answers, we integrate trait measurements, a resource–host–parasite model and experimental epidemics with plankton. This combination reveals how parasites may decrease or increase host density. This spectrum of outcomes reflects tension between parasite‐driven mortality (a density‐mediated effect) and foraging depression upon contact with parasite propagules (a trait‐mediated one).In the model, mortality rises when higher susceptibility to infection increases infection prevalence. These large epidemics release resources while suppressing hosts (creating a trophic cascade). In contrast, when hosts are less susceptible and parasites depress host foraging, a resource feedback can elevate host density during epidemics (creating a hydra effect), particularly at higher carrying capacity of resources. This combination creates the hydra effect because it elevates primary production relative to per‐host consumption of resources (two key determinants of host density).We test these predictions qualitatively with trait measurements and a mesocosm experiment. Clonal lines of zooplankton hosts differed in their foraging depression and susceptibility. Then, with these different host genotypes, we created epidemics in mesocosms supplied with either low or high nutrients (to manipulate carrying capacity). Hydra effects and trophic cascades both arose and in the trait–nutrient combinations predicted by the model.Hence, we show how tension between trait‐ and density‐mediated effects of parasites can govern the fate of host density during epidemics—from trophic cascades to hydra effects.Read the free Plain Language Summary for this article on the Journal blog.