UBC Theses and Dissertations
Models for tent caterpillar-virus interactions Beukema, Sarah Jenelle
Many species of forest Lepidoptera show eight to twelve year population cycles which may involve viral disease. To examine possible interactions between viral disease and population cycles of forest Lepidoptera I explored some models for insect-virus dynamics. All of the models produced population oscillations in their original form. However, after they were modified to conform more closely to the tent caterpillar system, none of the models produced realistic cycles. I then developed a new model specifically for the tent caterpillar system that included important features such as: reduced fecundity of individuals that had been exposed to the disease, transmission of the disease from mother to progeny, a free-living infective stage of the virus, and a horizontal transmission rate that varied with the larval stage, the number of individuals, and amount of virus present. Cyclic dynamics resulted from some simulations. The parameters producing the cycles were similar to actual data. However, unlike natural populations of tent caterpillars, in the simulated population the average fecundity decreased before the population started to decline and survival decreased at approximately the same time as the population. Important further research in the field should include investigation of the distribution and survival of free-living virus and factors that would reduce caterpillar survival at peak populations but not affect fecundity.
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