Data from: Keystone nonconsumptive effects within a diverse predator community

The number of prey killed by diverse predator communities is determined by complementarity and interference among predators, and by traits of particular predator species. However, it is less clear how predators' nonconsumptive effects (NCEs) scale with increasing predator biodiversity. We examined NCEs exerted on Culex mosquitoes by a diverse community of aquatic predators. In the field, mosquito larvae co-occurred with differing densities and species compositions of mesopredator insects; top predator dragonfly naiads were present in roughly half of surveyed water bodies. We reproduced these predator community features in artificial ponds, exposing mosquito larvae to predator cues and measuring resulting effects on mosquito traits throughout development. Nonconsumptive effects of various combinations of mesopredator species reduced the survival of mosquito larvae to pupation, and reduced the size and longevity of adult mosquitoes that later emerged from the water. Intriguingly, adding single dragonfly naiads to ponds restored survivorship of larval mosquitoes to levels seen in the absence of predators, and further decreased adult mosquito longevity compared with mosquitoes emerging from mesopredator treatments. Behavioral observations revealed that mosquito larvae regularly deployed "diving" escape behavior in the presence of the mesopredators, but not when a dragonfly naiad was also present. This suggests that dragonflies may have relaxed NCEs of the mesopredators by causing mosquitoes to abandon energetically costly diving. Our study demonstrates that adding one individual of a functionally unique species can substantially alter community-wide NCEs of predators on prey. For pathogen vectors like mosquitoes, this could in turn influence disease dynamics.

多样捕食者群落的猎物捕杀量，取决于捕食者间的互补作用与干扰效应，以及特定捕食者物种的功能性状。然而，目前学界对捕食者的非消耗性效应（nonconsumptive effects, NCEs）如何随捕食者生物多样性提升而变化仍不甚明晰。
本研究针对水生捕食者多样群落对库蚊（Culex）产生的非消耗性效应展开探究。野外调查显示，蚊幼虫与不同密度、物种组成的中级捕食性昆虫共存；约半数受访水体中存在顶级捕食者——蜻蜓稚虫。
研究人员在人工池塘中复现了上述捕食者群落特征，将蚊幼虫暴露于捕食者信号线索环境中，并全程监测其发育过程中的相关性状变化。结果发现，多种中级捕食者物种组合产生的非消耗性效应，会降低蚊幼虫化蛹前的存活率，同时降低最终羽化成虫的体型与寿命。
值得关注的是，向池塘中投放单只蜻蜓稚虫后，蚊幼虫的存活率恢复至无捕食者环境中的水平，且相较于仅接受中级捕食者处理的实验组，成虫寿命进一步缩短。
行为观测结果表明，蚊幼虫在遭遇中级捕食者时会频繁展现“潜水逃逸”行为，但当同时存在蜻蜓稚虫时则不会出现该行为。
这一现象提示，蜻蜓稚虫可能通过促使蚊幼虫放弃耗能极高的潜水行为，从而削弱了中级捕食者带来的非消耗性效应。
本研究证实，引入一只具备独特功能生态位的物种，即可显著改变捕食者群落对猎物的整体非消耗性效应。对于蚊这类病原媒介生物而言，该效应或可进一步影响疾病传播动态。