Irruptive population dynamics are affected by both bottom-up and top-down processes. However, trophic chains such as this do not exist in isolation. Indeed, the food webs in which irruptive taxa are nested include multiple connections with and between trophic levels. We are investigating how variation in the amount of available host affects irruptive population dynamics when assuming that a reduction in the amount of host (e.g., confiers) increases the availability non-host (e.g., deciduous species) available for other herbivores, which in turn serves as a reservoir for shared natural enemies. This work is motivated by the spruce budworm outbreak system in which forest diversity has been shown to reduce the intensity of defoliation, presumabley thorugh an influence on a diverse community of associated generalist parasitoids. Using mathematical models (ODEs) to formalize this conceptual model, we are specifically investigating under what conditions a manipulation of in host and non-host density can modulate the intensity of defoliator outbreaks.
Collaborators: V. Krivan (CAS), É. Filotas (TELUQ)