Effects of defense evolution and diet choice on population dynamics in a one-predator-two-prey system

The population dynamics of a one-predator-two-prey system were modeled. This model included the evolution of antipredator defense in the prey species and the optimal diet choice in the predator and was analyzed numerically using computer simulations. Results showed that defense evolution in the prey species tended to promote coexistence of the three species and, depending on parameters, reduced the amplitude of density fluctuations. Introducing optimal diet choice by the predator into the model also promoted coexistence and generally reduced density fluctuations. When the additive genetic variance for defense intensity was large (i.e., the evolutionary rate of defense was rapid), coexistence of the three species and stabilization of dynamics tended to be promoted. As a consequence, we concluded that (1) the evolution of antipredator defense can be an important factor in the persistence of a community, either with or without the optimal diet choice of predator; and (2) when population dynamics are combined with the evolutionary dynamics of trait development, the relative time scale of the two processes plays an important role in the stability of the system.