Department of Mathematical Sciences, University of Bath, Bath, United Kingdom.
Department of Mathematics, Simon Fraser University, Burnaby, British Columbia, Canada.
Evolution. 2023 Dec 2;77(12):2631-2641. doi: 10.1093/evolut/qpad178.
Hyperparasites (species which parasitize other parasites) are common in natural populations, affecting many parasitic taxa, including: eukaryotic parasites; bacterial and fungal pathogens. Hyperparasitism is therefore likely to shape the ecology and evolution of many host-parasite systems, representing a promising method for biocontrol (e.g., treating antimicrobial resistant infections). However, the eco-evolutionary consequences of hyperparasitism have received little attention. We use a host-parasite-hyperparasite model to explore how introducing a hyperparasite drives the evolution of parasite virulence, and what impact this has on the host population. We show when the introduction of a hyperparasite selects for higher or lower parasite virulence, and the changes in virulence experienced by the host population. Crucially, we show that variation in the direct effects of hyperparasites on virulence and transmission, and the probability of cotransmission, can lead to a previously unseen hysteresis effect, whereby small shifts in hyperparasite characteristics can lead to sudden shifts in parasite virulence. We also show that hyperparasites can induce diversification in parasite virulence, leading to the coexistence of high and low virulence strains. Our results show hyperparasites can have dramatic effects on the evolution of parasite virulence, and that the use of hyperparasites in biocontrol should be approached with caution.
重寄生蜂（寄生于其他寄生虫的物种）在自然种群中很常见，会影响许多寄生类群，包括真核寄生虫、细菌和真菌病原体。因此，重寄生很可能会影响许多宿主-寄生虫系统的生态和进化，是一种很有前途的生物防治方法（例如，治疗对抗生素有耐药性的感染）。然而，重寄生的生态进化后果却很少受到关注。我们使用一个宿主-寄生虫-重寄生蜂模型来探讨引入重寄生蜂如何驱动寄生虫毒力的进化，以及这对宿主种群有什么影响。我们展示了当引入重寄生蜂选择更高或更低的寄生虫毒力时，以及宿主种群经历的毒力变化。至关重要的是，我们表明，重寄生蜂对毒力和传播的直接影响的变化，以及共传播的可能性，可能导致以前未见过的滞后效应，即重寄生蜂特征的微小变化可能导致寄生虫毒力的突然变化。我们还表明，重寄生蜂可以诱导寄生虫毒力的多样化，导致高毒力和低毒力菌株共存。我们的结果表明，重寄生蜂可以对寄生虫毒力的进化产生巨大影响，因此在生物防治中使用重寄生蜂应该谨慎。
