Climate warming and species traits interact to influence predator performance, including individual feeding and growth rates. However, the effects of an important trait-predator foraging strategy-are largely unknown. We investigated the interactions between predator foraging strategy and temperature on two ectotherm predators: an active predator, the backswimmer Notonecta undulata, and a sit-and-wait predator, the damselfly Enallagma annexum. In a series of predator-prey experiments across a temperature gradient, we measured predator feeding rates on an active prey species, zooplankton Daphnia pulex, predator growth rates, and mechanisms that influence predator feeding: body speed of predators and prey (here measured as swimming speed), prey encounter rates, capture success, attack rates, and handling time. Overall, warming led to increased feeding rates for both predators through changes to each component of the predator's functional response. We found that prey swimming speed strongly increased with temperature. The active predator's swimming speed also increased with temperature, and together, the increase in predator and prey swimming speed resulted in two-fold higher prey encounter rates for the active predator at warmer temperatures. By contrast, prey encounter rates of the sit-and-wait predator increased four-fold with rising temperatures as a result of increased prey swimming speed. Concurrently, increased prey swimming speed was associated with a decline in the active predator's capture success at high temperatures, whereas the sit-and-wait predator's capture success slightly increased with temperature. We provide some of the first evidence that foraging traits mediate the indirect effects of warming on predator performance. Understanding how traits influence species' responses to warming could clarify how climate change will affect entire functional groups of species.

中文翻译：

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觅食策略介导变温捕食者-猎物对气候变暖的反应

气候变暖和物种特征相互作用以影响捕食者的表现，包括个体进食和生长速度。然而，一种重要的特征——捕食者觅食策略——的影响在很大程度上是未知的。我们研究了捕食者觅食策略和温度在两种变温捕食者身上的相互作用：一种活跃的捕食者，向后游泳的 Notoneecta undulata，和一种坐等捕食者，豆娘 Enallagma Annexum。在一系列跨越温度梯度的捕食者-猎物实验中，我们测量了捕食者对活跃猎物物种、浮游动物水蚤、捕食者生长速率和影响捕食者进食的机制的捕食率：捕食者和猎物的身体速度（这里测量为游泳速度）、猎物遭遇率、捕获成功率、攻击率和处理时间。全面的，通过改变捕食者功能反应的每个组成部分，变暖导致两种捕食者的摄食率增加。我们发现猎物的游泳速度随着温度的升高而显着增加。活跃捕食者的游泳速度也随着温度的升高而增加，并且捕食者和猎物游泳速度的增加导致活跃捕食者在温暖的温度下遇到猎物的几率增加了两倍。相比之下，由于猎物游泳速度的增加，随着温度的升高，坐等捕食者的猎物遭遇率增加了四倍。同时，猎物游泳速度的增加与高温下主动捕食者的捕获成功率下降有关，而坐等捕食者的捕获成功率随着温度的升高而略有增加。我们提供了一些初步证据，表明觅食性状介导了变暖对捕食者表现的间接影响。了解特征如何影响物种对变暖的反应可以阐明气候变化将如何影响物种的整个功能群。