Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn TR10 9FE, UK; Center for the Ecology of Infectious Diseases, University of Georgia, Athens, GA 30602, USA.
Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn TR10 9FE, UK; Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
J Theor Biol. 2021 Aug 21;523:110717. doi: 10.1016/j.jtbi.2021.110717. Epub 2021 Apr 14.
A substantial body of work has shown that local transmission selects for less acute, 'prudent' parasites that have lower virulence and transmission rates. This is because parasite strains with higher transmission rates 'self-shade' due to a combination of genetic correlations (self: clustered related parasite strains compete for susceptible individuals) and ecological correlations (shade: infected individuals clustering and blocking transmission). However, the interaction of ecological and genetic correlations alongside higher order ecological effects such as patch extinctions means that spatial evolutionary effects can be nuanced; theory has predicted that a relatively small proportion of local infection can select for highest virulence, such that there is a humped relationship between the degree of local infection and the harm that parasites are selected to cause. Here, we examine the separate roles of the interaction scales of reproduction and infection in the context of different degrees of pathogenic castration in determining virulence evolution outcomes. Our key result is that, as long as there is significant reproduction from infected individuals, local infection always selects for lower virulence, and that the prediction that a small proportion of local infection can select for higher virulence only occurs for highly castrating pathogens. The results emphasize the importance of demography for evolutionary outcomes in spatially structured populations, but also show that the core prediction that parasites are prudent in space is reasonable for the vast majority of host-parasite interactions and mixing patterns in nature.
大量研究表明，本地传播会选择毒力和传播率较低的不那么急性的“谨慎”寄生虫。这是因为具有较高传播率的寄生虫株由于遗传相关性（自我：聚类相关的寄生虫株竞争易感个体）和生态相关性（阴影：感染个体聚类和阻断传播）的组合而“自我遮蔽”。然而，生态和遗传相关性的相互作用以及更高阶的生态效应（如斑块灭绝）意味着空间进化效应可能是微妙的；理论预测，相对较小比例的本地感染可以选择最高的毒力，因此，寄生虫被选择造成的伤害与本地感染程度之间存在驼峰关系。在这里，我们在不同程度的致病性去势的背景下，分别研究了繁殖和感染的相互作用尺度在决定毒力进化结果方面的作用。我们的主要结果是，只要感染个体有显著的繁殖，本地感染总是会选择低毒力，而一小部分本地感染可以选择更高毒力的预测仅适用于高度去势的病原体。研究结果强调了人口统计学对空间结构种群中进化结果的重要性，但也表明，寄生虫在空间上谨慎的核心预测对于自然界中绝大多数的宿主-寄生虫相互作用和混合模式是合理的。
