Laboratório de Ecologia, Instituto de Biociências, Universidade Federal do Mato Grosso do Sul, Campo Grande, MS, Brazil.
Departamento de Ecologia, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil.
J Anim Ecol. 2022 Oct;91(10):2023-2036. doi: 10.1111/1365-2656.13777. Epub 2022 Jul 30.
The emphasis on mechanisms governing the interaction among predators (e.g. cooperation, competition or intraguild predation) has driven the understanding of multiple-predator effects on prey survival and dynamics. However, overwhelming evidence shows that prey can adaptively respond to predators, exhibiting multiple defensive phenotypes to cope with predation. Nevertheless, there is still a relatively scarce theory connecting the emergence of prey defences in complex multi-predator scenarios and their ecological consequences. Using a mathematical approach, we evaluated the prevalence of defended prey phenotypes as a function of predator-induced mortality in a two-predator system, and how prey and phenotype dynamics affect trophic cascades. We also evaluated such responses when prey manifests a general defence against both predators (i.e. risk reducing) or a specialized defence against one predator at the expense of defence against the other predator (i.e. risk trade-off), and when such phenotypes induce fitness and foraging costs. We showed that the emergence of defended phenotypes under multiple predators depends on predator-induced mortality rates, the magnitude of phenotype costs and the effect of the defensive phenotype on the performance of all predators. Risk-reducing phenotypes enhance prioritized responses to predators with high killing rates, but prioritized responses are diminished when prey manifest risk trade-off phenotypes. Finally, we showed that resource abundance across the predation gradient directly depends on the prevalence of certain prey phenotypes and their effect on foraging costs. Ultimately, our results depict the implications of prey defences on prey and basal resources abundance in a multiple predators' environment, highlighting the role of the identity of defensive strategies in mediating the strength and nature of trophic cascades, via consumptive or non-consumptive effects.
强调控制捕食者之间相互作用的机制（例如合作、竞争或种内捕食），推动了对捕食者对猎物生存和动态影响的理解。然而，压倒性的证据表明，猎物可以适应捕食者的存在，表现出多种防御表型来应对捕食。尽管如此，将猎物防御的出现与复杂的多捕食者情景及其生态后果联系起来的理论仍然相对较少。我们使用数学方法，评估了在两种捕食者系统中，作为捕食者诱导死亡率函数的防御性猎物表型的普遍性，以及猎物和表型动态如何影响营养级联。我们还评估了当猎物对两种捕食者都表现出一般性防御（即降低风险）或专门针对一种捕食者的防御（即风险权衡），以及当这些表型引起适应性和觅食成本时，会出现这种反应。我们表明，在多种捕食者下，防御性表型的出现取决于捕食者诱导的死亡率、表型成本的大小以及防御性表型对所有捕食者表现的影响。降低风险的表型增强了对高杀伤率捕食者的优先响应，但当猎物表现出风险权衡表型时，优先响应会减少。最后，我们表明，在捕食梯度上的资源丰度直接取决于某些猎物表型的普遍性及其对觅食成本的影响。最终，我们的结果描述了猎物防御在多捕食者环境中对猎物和基础资源丰度的影响，强调了防御策略的身份在通过消耗或非消耗效应调节营养级联的强度和性质方面的作用。
