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 fluctuatio ns in insect herbivore populations. However, experimental demonstrations of induced resistance affecting longterm herbivore population dynamics are la cking, and few models find that induced resistance drives cycles in herbivo re populations. Here a simulation model is used to explore the influence of characteristics of the plant-herbivore system on the likelihood that induc ed resistance can regulate or drive cycles in herbivore populations. Result s of this model suggest that induced resistance may cause fluctuations in h erbivore populations under more conditions than previously thought. The mod el incorporates parameters for the timing and strength of induced resistanc e and for herbivore mobility and host-plant selectivity Results are present ed for two configurations of the model: forest (many herbivore generations per plant generation) and crop (few herbivore generations per plant generat ion). In simulations of this model, induced resistance in the absence of ot her density-dependent factors can regulate herbivore populations. Induced r esistance can also drive fluctuations in herbivore populations when there i s a time lag between damage and the onset of induced resistance. The time l ag required to cause fluctuations depends on characteristics such as the st rength of induced resistance and the mobility of the herbivore.