Meeting Abstract

P2.74  Tuesday, Jan. 5  Modeling caterpillar responses to inducible plant defenses VIG, D.K.*; KERKHOFF, A.J.; Kenyon College; Kenyon College kerkhoffa@kenyon.edu

Many herbivores have the ability to defoliate an entire plant within days. In response to herbivory, some plants generate toxic chemicals in their leaves. These inducible defenses are unique for each species of plant. For example, tobacco, Nicotiana attenuata, increases nicotine production when the caterpillar, Manduca sexta, starts to feed on it. We explored caterpillar growth and feeding behavior in the context of inducible plant defenses by creating a dynamic state variable model. At each time step the caterpillar had a “choice” to either stay on the current plant or move to a new plant. We compared the optimal life histories of caterpillars growing on plants with a low induction rates to those growing on plants with high induction rates. Caterpillars that were adapted to a lower induction rate tended to stay on a plant longer and achieve higher average fitness than caterpillars adapted to a higher induction rate. However, when caterpillars that were adapted to a low induction rate were exposed to an environment with a high induction rate, they achieved lower average fitness than caterpillars adapted to that environment, even though they displayed similar behavior. Similarly, caterpillars adapted to a high induction rate tended to remain on low induction rate plants for a longer time, but could not match the average fitness level of caterpillars adapted to the less stressful environment. Thus, variation in the inducible defenses has the potential to act as a selective force on caterpillar behavior. The generality of the model will also allow future studies to examine whether caterpillar behavior can change in response to inducible communication between plants.