Department of Biological Sciences, University of Arkansas, Fayetteville, AR, 72701, USA.
Ecol Lett. 2020 Jun;23(6):951-961. doi: 10.1111/ele.13491. Epub 2020 Mar 29.
Predators have a key role shaping competitor dynamics in food webs. Perhaps the most obvious way this occurs is when predators reduce competitor densities. However, consumption could also generate phenotypic selection on prey that determines the strength of competition, thus coupling consumptive and trait-based effects of predators. In a mesocosm experiment simulating fish predation on damselflies, we found that selection against high damselfly activity rates - a phenotype mediating predation and competition - weakened the strength of density dependence in damselfly growth rates. A field experiment corroborated this finding and showed that increasing damselfly densities in lakes with high fish densities had limited effects on damselfly growth rates but generated a precipitous growth rate decline where fish densities were lower - a pattern expected because of spatial variation in selection imposed by predation. These results suggest that accounting for both consumption and selection is necessary to determine how predators regulate prey competitive interactions.
捕食者在塑造食物网中竞争动态方面起着关键作用。这种情况最明显的发生方式是当捕食者降低竞争者的密度时。然而，捕食也可能对猎物产生表型选择，从而决定竞争的强度，从而将捕食者的消耗性和基于特征的影响联系起来。在一个模拟鱼类捕食蜻蜓的中观实验中，我们发现，对高蜻蜓活动率（一种介导捕食和竞争的表型）的选择减弱了蜻蜓生长率的密度依赖性。一项野外实验证实了这一发现，并表明在鱼类密度高的湖泊中增加蜻蜓密度对蜻蜓生长率的影响有限，但在鱼类密度较低的地方会导致蜻蜓生长率急剧下降——这种模式是由于捕食造成的空间选择变化所致。这些结果表明，为了确定捕食者如何调节猎物的竞争相互作用，有必要同时考虑消耗和选择。
