Abstract：
Parasites are known to have direct effects on host dispersal ability and motivation. Yet, parasites have a variety of impacts on host populations, including shaping predation and cannibalism rates, and therefore may also have indirect effects on host dispersal; these indirect pathways have not been studied. We tested the hypothesis that parasites influence host dispersal through effects on cannibalism using backswimmers (Notonecta undulata) and Hydrachnidia freshwater mites. Mite parasitism impedes swimming in backswimmers, which we found increased their vulnerability to cannibalism. We imposed a manipulation that varied cannibalism rates across experimental populations consisting of a mix of backswimmers with and without simulated parasites. Using simulated parasites allowed us to examine the effects of cannibalism without introducing infection risk. We found that the odds of dispersal for infected backswimmers increased by 2.25× with every 10% increase in the risk of being cannibalized, and the odds of dispersal for healthy backswimmers increased by 2.34× for every additional infected backswimmer they consumed. Our results suggest that cannibalism was used as an energy source for dispersal for healthy individuals, while the risk of being eaten motivated dispersal in infected individuals. These results elucidate the complex ways that parasites impact host populations and strengthen our understanding of host-parasite interactions, including host and parasite population stability and spread. This article is part of the theme issue \'Diversity-dependence of dispersal: interspecific interactions determine spatial dynamics\'.
摘要：
已知寄生虫对宿主分散能力和动机有直接影响。然而，寄生虫对宿主种群有多种影响，包括塑造捕食和食人族的比例，因此也可能对寄主扩散有间接影响；这些间接途径尚未研究。我们检验了以下假设：寄生虫通过使用反向游泳者（Notonectaundulata）和Hydrachnidia淡水螨对同类相食行为的影响来影响宿主的扩散。螨虫寄生阻碍了游泳者的游泳，我们发现这增加了他们自相残杀的脆弱性。我们实施了一种操作，该操作在实验人群中改变了同类相食率，这些实验人群包括有和没有模拟寄生虫的反向游泳者。使用模拟的寄生虫使我们能够检查同类相食的影响，而不会引入感染风险。我们发现，受感染的反向游泳者的扩散几率增加了2.25倍，被蚕食的风险每增加10％，健康的反向游泳者每消耗一次受感染的反向游泳者，扩散的可能性就增加了2.34倍。我们的结果表明，食人族被用作健康个体分散的能量来源，而被吃掉的风险促使被感染的个体扩散。这些结果阐明了寄生虫影响宿主种群的复杂方式，并加强了我们对宿主-寄生虫相互作用的理解。包括宿主和寄生虫种群的稳定性和传播。本文是主题问题“扩散的多样性依赖性：种间相互作用决定空间动力学”的一部分。
