Ashby Ben, King Kayla C
Department of Mathematical Sciences University of Bath Bath BA2 7AY United Kingdom.
Department of Integrative Biology University of California Berkeley Berkeley 94720 California.
Evol Lett. 2017 Aug 31;1(4):211-221. doi: 10.1002/evl3.19. eCollection 2017 Sep.
Hosts are often infected by multiple parasite species, yet the ecological and evolutionary implications of the interactions between hosts and coinfecting parasites are largely unknown. Most theoretical models of evolution among coinfecting parasites focus on the evolution of virulence, but parasites may also evolve to protect their hosts by reducing susceptibility (i.e., conferring resistance) to other parasites or reducing the virulence of coinfecting parasites (i.e., conferring tolerance). Here, we analyze the eco-evolutionary dynamics of parasite-conferred resistance and tolerance using coinfection models. We show that both parasite-conferred resistance and tolerance can evolve for a wide range of underlying trade-offs. The shape and strength of the trade-off qualitatively affects the outcome causing shifts between the minimisation or maximization of protection, intermediate stable strategies, evolutionary branching, and bistability. Furthermore, we find that a protected dimorphism can readily evolve for parasite-conferred resistance, but find no evidence of evolutionary branching for parasite-conferred tolerance, in general agreement with previous work on host evolution. These results provide novel insights into the evolution of parasite-conferred resistance and tolerance, and suggest clues to the underlying trade-offs in recent experimental work on microbe-mediated protection. More generally, our results highlight the context dependence of host-parasite relationships in complex communities.
宿主常常会被多种寄生虫物种感染，然而宿主与共感染寄生虫之间相互作用的生态和进化意义在很大程度上尚不清楚。大多数关于共感染寄生虫进化的理论模型都聚焦于毒力的进化，但寄生虫也可能通过降低对其他寄生虫的易感性（即赋予抗性）或降低共感染寄生虫的毒力（即赋予耐受性）来进化以保护其宿主。在此，我们使用共感染模型分析寄生虫赋予的抗性和耐受性的生态进化动态。我们表明，在广泛的潜在权衡情况下，寄生虫赋予的抗性和耐受性都可以进化。权衡的形式和强度在质量上影响结果，导致在保护的最小化或最大化、中间稳定策略、进化分支和双稳态之间发生转变。此外，我们发现对于寄生虫赋予的抗性，受保护的二态性很容易进化，但总体上没有发现寄生虫赋予的耐受性存在进化分支的证据，这与之前关于宿主进化的研究一致。这些结果为寄生虫赋予的抗性和耐受性的进化提供了新的见解，并为微生物介导保护的近期实验工作中潜在的权衡提供了线索。更普遍地说，我们的结果突出了复杂群落中宿主 - 寄生虫关系对环境的依赖性。
