Changes in prey body size differentially reduces predation risk across predator and prey abundances

Trophic interactions underpin the structure of ecological communities by describing the rates at which consumers exploit their resources. The rates at which predators consume their prey are influenced by prey traits, with many species inducing defensive modifications to prey traits following the threat of predation. Here we use different clonal lines of the protist Paramecium being consumed by Stenostomum predators to highlight how differences in prey traits impact rates of predation. Clonal lines differed in their body width traits, and in their ability to induce changes in body width. By using a factorial cross of predator and prey abundances for different clonal lines we demonstrate how evolutionary or induced alterations in prey traits can impact the relative threat of predation. Our experiments show how interference among predators impacts predation rate, and how increased body width increased predator handling times. Given that reductions in the strength of interspecific interactions are associated with increased levels of overall community stability, our results indicate how individual level changes may scale up to impact whole communities.

Automated summary

Trophic interactions determine the structure of ecological communities by describing the rates at which consumers utilize resources. Prey traits play a role in influencing the rates at which predators consume them, and many species exhibit defensive modifications in response to predation threats. This study investigates how differences in prey traits, specifically body width, impact the rates of predation by Stenostomum predators on different clonal lines of Paramecium protists. The results demonstrate how changes in prey traits, whether evolutionary or induced, can affect the relative threat of predation, and how interference among predators and increased body width can influence predation rates.