Ecological consequences of the evolution of qualitatively different defense strategies

Background/Question/Methods Understanding how ecological and evolutionary processes feed back on one another is essential for understanding trait expression. Previous theory has shown that different curvatures of the foraging--predation risk tradeoff lead to the evolution of qualitatively different predator defense strategies. Linear tradeoffs are predicted to lead to life history defenses, while highly nonlinear tradeoffs are predicted to lead to behavioral defenses. For moderately nonlinear tradeoffs, positive interactions between the foraging—predation risk tradeoff and the growth—reproduction tradeoff lead to the evolution of integrated multi-defense strategies. However, this work considered only static resource and predator environments. Here, I explore how allowing resources and predators to be dynamic affects the evolution of defense strategy and explore the ecological consequences of different defense strategies.

Results/Conclusions I show that different shapes of the foraging—predation risk tradeoff lead to qualitatively different defense strategies, but that these different strategies lead to very different ecological consequences. This confirms the prediction of the simpler theory and extends it to encompass more biological realism. I show that populations of individuals employing life history defenses reduce resource densities much more than populations of individuals employing behavioral defenses, suggesting that trait-mediated indirect effects on other species will be much stronger in the case of behavioral defenses. Using an adaptive dynamics approach, I also investigate the circumstances under which different defense strategies can be invaded by competing strategies and show that under moderately nonlinear tradeoffs, there can be coexistence of fast (life history) and slow (behavioral) defense strategies.