Am Nat. 2021 Feb;197(2):216-235. doi: 10.1086/712351. Epub 2020 Dec 23.
AbstractHyperparasitism denotes the natural phenomenon where a parasite infecting a host is in turn infected by its own parasite. Hyperparasites can shape the dynamics of host-parasite interactions and often have a deleterious impact on pathogens, an important class of parasites, causing a reduction in their virulence and transmission rate. Hyperparasitism thus could be an important tool of biological control. However, host-parasite-hyperparasite systems have so far been outside the mainstream of modeling studies, especially those dealing with eco-evolutionary aspects of species interactions. Here, we theoretically explore the evolution of life-history traits in a generic host-parasite-hyperparasite system, focusing on parasite virulence and the positive impact that hyperparasitism has on the host population. We also explore the coevolution of life-history traits of the parasite and hyperparasite, using adaptive dynamics and quantitative genetics frameworks to identify evolutionarily singular strategies. We find that in the presence of hyperparasites, the evolutionarily optimal pathogen virulence generally shifts toward more virulent strains. However, even in this case the use of hyperparasites in biocontrol could be justified, since overall host mortality decreases. An intriguing possible outcome of the evolution of the hyperparasite can be its evolutionary suicide.
摘要 重寄生现象是指一种寄生虫感染宿主的同时，又被自身寄生虫感染的自然现象。重寄生现象可以影响宿主-寄生虫相互作用的动态，并且经常对病原体（寄生虫的一个重要类别）产生有害影响，导致其毒力和传播率降低。因此，重寄生现象可能是生物防治的重要工具。然而，迄今为止，宿主-寄生虫-重寄生系统一直处于建模研究的主流之外，特别是那些涉及物种相互作用的生态进化方面的研究。在这里，我们从理论上探讨了一般的宿主-寄生虫-重寄生系统中生活史特征的进化，重点关注寄生虫的毒力以及重寄生对宿主种群的积极影响。我们还使用适应动态和数量遗传学框架来探索寄生虫和重寄生生物生活史特征的共同进化，以确定进化上的奇异策略。我们发现，在存在重寄生的情况下，寄生虫的进化最优毒力通常会向更具毒性的菌株转移。然而，即使在这种情况下，使用重寄生进行生物防治也可能是合理的，因为宿主死亡率总体上降低了。重寄生进化的一个有趣的可能结果可能是其进化自杀。
