Rice University, Houston, Texas, 77005.
Evolution. 2019 Nov;73(11):2189-2203. doi: 10.1111/evo.13843. Epub 2019 Sep 24.
The majority of organisms host multiple parasite species, each of which can interact with hosts and competitors through a diverse range of direct and indirect mechanisms. These within-host interactions can directly alter the mortality rate of coinfected hosts and alter the evolution of virulence (parasite-induced host mortality). Yet we still know little about how within-host interactions affect the evolution of parasite virulence in multi-parasite communities. Here, we modeled the virulence evolution of two coinfecting parasites in a host population in which parasites interacted through cross immunity, immune suppression, immunopathology, or spite. We show (1) that these within-host interactions have different effects on virulence evolution when all parasites interact with each other in the same way versus when coinfecting parasites have unique interaction strategies, (2) that these interactions cause the evolution of lower virulence in some hosts, and higher virulence in other hosts, depending on the hosts infection status, and (3) that for cross immunity and spite, whether parasites increase or decrease the evolutionarily stable virulence in coinfected hosts depended on interaction strength. These results improve our understanding of virulence evolution in complex parasite communities, and show that virulence evolution must be understood at the community scale.
大多数生物都携带有多种寄生虫，每种寄生虫都可以通过多种直接和间接的机制与宿主和竞争者相互作用。这些宿主内的相互作用可以直接改变共感染宿主的死亡率，并改变寄生虫毒力（寄生虫引起的宿主死亡率）的进化。然而，我们仍然不太了解宿主内的相互作用如何影响多寄生虫群落中寄生虫毒力的进化。在这里，我们在一个宿主种群中模拟了两种共感染寄生虫的毒力进化，其中寄生虫通过交叉免疫、免疫抑制、免疫病理学或恶意相互作用。我们表明：（1）当所有寄生虫以相同的方式相互作用时，与当共感染寄生虫具有独特的相互作用策略时，这些宿主内的相互作用对毒力进化有不同的影响；（2）这些相互作用导致一些宿主的毒力进化降低，而其他宿主的毒力进化升高，这取决于宿主的感染状态；（3）对于交叉免疫和恶意，寄生虫是否增加或降低共感染宿主中进化稳定的毒力取决于相互作用强度。这些结果提高了我们对复杂寄生虫群落中毒力进化的理解，并表明毒力进化必须在群落尺度上进行理解。
