How functional response and productivity modulate intraguild predation

Numerous models have been developed to predict the effect of environmental productivity on the coexistence of prey and predators within the three-species module of intraguild predation. Theoretical models have mainly used Holling Type I and Type II functional response, the latter typically best describing the functional response of a predator. However, no empirical study has simultaneously examined the form of the functional response and the effect of prey density on intraguild interactions. This is surprising considering that the strength of the functional response is crucially important for the stability of simple predator-prey systems and the persistence, sustainability and biodiversity of communities. In this study, we first developed a linear and a nonlinear functional response model for intraguild predators and next used a plant-aphid-predator mesocosm to parameterize the models and test their predictions at different prey densities. As expected, the assumptions of the linear model are not supported by empirical results which lead to systemic overestimation of the predation rate and the intensity of intraguild predation. On the other hand, the predictions of the nonlinear functional response model fit very well with experimental observations mainly because key behavioral characteristics such as handling time are integrated in this model. The nonlinear model is thus a good predictor of intraguild predation and allows a better understanding of how environmental productivity and predator behavior influence the occurrence and outcome of multiple predator interactions.