The influence of plant and herbivore characteristics on the interaction between induced resistance and herbivore population dynamics

Induced plant resistance may contribute to regulating or driving fluctuations in insect herbivore populations. However, experimental demonstrations of induced resistance affecting longterm herbivore population dynamics are lacking, and few models find that induced resistance drives cycles in herbivore populations. Here a simulation model is used to explore the influence of characteristics of the plant-herbivore system on the likelihood that induced resistance can regulate or drive cycles in herbivore populations. Results of this model suggest that induced resistance may cause fluctuations in herbivore populations under more conditions than previously thought. The model incorporates parameters for the timing and strength of induced resistance and for herbivore mobility and host-plant selectivity Results are presented for two configurations of the model: forest (many herbivore generations per plant generation) and crop (few herbivore generations per plant generation). In simulations of this model, induced resistance in the absence of other density-dependent factors can regulate herbivore populations. Induced resistance can also drive fluctuations in herbivore populations when there is a time lag between damage and the onset of induced resistance. The time lag required to cause fluctuations depends on characteristics such as the strength of induced resistance and the mobility of the herbivore.