BioSciences, Rice University, Houston, Texas, USA.
Ecology. 2022 Jul;103(7):e3704. doi: 10.1002/ecy.3704. Epub 2022 May 25.
Although there is mounting evidence indicating that the relative timing of predator and prey phenologies determines the outcome of trophic interactions, we still lack a comprehensive understanding of how the environmental context (e.g., abiotic conditions) influences this relationship. Environmental conditions not only frequently drive shifts in phenologies, but they can also affect the very same processes that mediate the effects of phenological shifts on species interactions. Therefore, identifying how environmental conditions shape the effects of phenological shifts is key to predicting community dynamics across a heterogeneous landscape and how they will change with ongoing climate change in the future. Here I tested how environmental conditions shape the effects of phenological shifts by experimentally manipulating temperature, nutrient availability, and relative phenologies in two predator-prey freshwater systems (mole salamander-bronze frog vs. dragonfly larvae-leopard frog). This allowed me to (1) isolate the effects of phenological shifts and different environmental conditions; (2) determine how they interact; and (3) evaluate how consistent these patterns are across different species and environments. I found that delaying prey arrival dramatically increased predation rates, but these effects were contingent on environmental conditions and the predator system. Although nutrient addition and warming both significantly enhanced the effect of arrival time, their effect was qualitatively different across systems: Nutrient addition enhanced the positive effect of early arrival in the dragonfly-leopard frog system, whereas warming enhanced the negative effect of arriving late in the salamander-bronze frog system. Predator responses varied qualitatively across predator-prey systems. Only in the system with a strong gape limitation were predators (salamanders) significantly affected by prey arrival time and this effect varied with environmental context. Correlations between predator and prey demographic rates suggest that this was driven by shifts in initial predator-prey size ratios and a positive feedback between size-specific predation rates and predator growth rates. These results highlight the importance of accounting for temporal and spatial correlations of local environmental conditions and gape limitation when predicting the effects of phenological shifts and climate change on predator-prey systems.
尽管越来越多的证据表明捕食者和猎物物候的相对时间决定了营养相互作用的结果，但我们仍然缺乏对环境背景（如非生物条件）如何影响这种关系的全面了解。环境条件不仅经常驱动物候的转变，而且还会影响调节物候转变对物种相互作用影响的相同过程。因此，确定环境条件如何塑造物候转变的影响是预测跨异质景观的群落动态以及它们将如何随着未来气候变化而变化的关键。在这里，我通过在两个淡水捕食者-猎物系统（鼹鼠蝾螈-青铜蛙与蜻蜓幼虫-豹蛙）中实验性地操纵温度、养分可用性和相对物候来测试环境条件如何塑造物候转变的影响。这使我能够：(1) 分离物候转变和不同环境条件的影响；(2) 确定它们如何相互作用；(3) 评估这些模式在不同物种和环境中是否一致。我发现，延迟猎物到达会显著增加捕食率，但这些影响取决于环境条件和捕食者系统。尽管养分添加和变暖都显著增强了到达时间的影响，但它们在不同系统中的作用是定性不同的：养分添加增强了蜻蜓-豹蛙系统中早期到达的积极影响，而变暖则增强了在蝾螈-青铜蛙系统中晚期到达的负面影响。捕食者的反应在捕食者-猎物系统中是定性不同的。只有在具有强烈口裂限制的系统中，捕食者（蝾螈）才会受到猎物到达时间的显著影响，并且这种影响随环境背景而变化。捕食者和猎物人口率之间的相关性表明，这是由初始捕食者-猎物大小比的变化以及大小特异性捕食率和捕食者生长率之间的正反馈驱动的。这些结果强调了在预测物候转变和气候变化对捕食者-猎物系统的影响时，考虑当地环境条件和口裂限制的时间和空间相关性的重要性。
