Many herbivorous insects show fluctuating population dynamics over time, and these dynamics have been attributed to interactions with parasitoids, with predators, or with their host plants. For the interactions between herbivores and plants in particular, changes in food availability can drive herbivore fluctuations. After herbivory, plants can show two possible adaptive mechanisms: overcompensation, where plants produce more aboveground biomass than was removed by the herbivores, or allocation of biomass to inedible belowground structures. The effects of overcompensatory regrowth and belowground allocation on herbivore population dynamics have been studied separately in models, and both may result in fluctuations. However, in real systems, these two processes are likely very closely linked. Overcompensation requires stored energy, and belowground structures may well provide this. Thus, it is critical that we understand the joint influence of these two plant responses on herbivore dynamics. In this study, we extend a previous model for perennial plants with the ability to allocate resources belowground and univoltine herbivores that feed aboveground, by adding post-damage overcompensation. We analyze the new model to investigate what conditions drive or dampen fluctuations in the herbivore population.
Results/Conclusions
By examining the temporal population dynamics of plants and herbivores, we derive conditions expected to lead to stable or cyclic coexistence of plants and herbivores. Our result shows that how strong the plants overcompensate, how sensitive the herbivores are to food limitation, and how and when the resource is allocated between aboveground and belowground biomass can affect if the populations go extinct or show stable or certain types of cyclic dynamics. Comparing our results with previous models highlights the importance of incorporating both overcompensation and belowground storage into the model when study the interaction between overcompensating plants and their insect herbivores.