A host immune hormone modifies parasite species interactions and epidemics: insights from a field manipulation.

Parasite epidemics can depend on priority effects, and parasite priority effects can result from the host immune response to prior infection. Yet we lack experimental evidence that such immune-mediated priority effects influence epidemics. To address this research gap, we manipulated key host immune hormones, then measured the consequences for within-host parasite interactions, and ultimately parasite epidemics in the field. Specifically, we applied plant immune-signaling hormones to sentinel plants, embedded into a wild host population, and tracked foliar infections caused by two common fungal parasites. Within host individuals, priority effects were altered by the immune-signaling hormone, salicylic acid. Scaling up from within-host interactions, hosts treated with salicylic acid experienced lower prevalence of a less aggressive parasite, increased burden of infection by a more aggressive parasite, and experienced fewer coinfections. Together, these results indicate that by altering w...

寄生虫流行病可依赖于优先效应（priority effects），而寄生虫的优先效应可源于宿主对预先感染的免疫应答（host immune response）。然而目前尚缺乏实验证据表明这类免疫介导的优先效应会对流行病产生影响。为填补这一研究空白，我们调控了关键宿主免疫激素，随后测定了宿主体内寄生虫互作的相关效应，并最终追踪了野外环境中的寄生虫流行病。具体而言，我们将植物免疫信号激素（plant immune-signaling hormones）施加于嵌入野生宿主种群的哨兵植株（sentinel plants），并追踪了两种常见真菌寄生虫引发的叶部侵染情况。在单一个体宿主内，优先效应可被免疫信号激素水杨酸（salicylic acid）改变。从宿主体内互作尺度向上外推，经水杨酸处理的宿主，其感染致病力较弱的寄生虫的流行率更低，感染致病力较强的寄生虫的负荷却更高，且共侵染事件也更少。综上，这些结果表明，通过改变w...