MONDAY, March 10, 2003

3:00 PM

CAB 657

Dr. Christina Cobbold

Department of Mathematical & Statistical Sciences
University of Alberta


Spatial and temporal impacts of parasitoid emergence time on the forest tent caterpillar


The forest tent caterpillar is a mass defoliator of trembling aspen and acts as a host for a number of fly and wasp parasitoid species. The caterpillar population periodically reaches outbreak densities, which can have a significant impact on tree growth. We have developed a discrete time model which incorporates the relative timing of host density dependence and parasitism allowing for concurrent occurrence of these events. We begin by examining a non-spatial model to study how parasitoid species effects the periodic outbreak of the forest tent caterpillar. Our non-spatial system builds on previous host-parasitoid models which had only incorporated the sequential order of parasitism and density dependence, our model permits the two mechanisms to occur simultaneously. Our model includes the impact of host density dependent mortality on parasitoid survivorship and we experimentally estimate this quantity. A model which includes the relative timing of parasitism and density dependence frequently predicts different dynamics compared to a model which neglects this timing. Even when both models predict population cycles, the period and amplitude differs significantly which has predictive implications for the forest tent caterpillar system. We also examine the effect of introducing space into our host-parasitoid model. This reveals interesting results for the interaction between parasitoid timing and forest size.