Population ecology of an endemic and an invasive species

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The causes and consequences of population dynamics are the domain of population ecologists.  Population dynamics of endemic and exotic species often differ in that outbreaks of endemic populations are temporary while those of exotic species are persistent. the most striking dynamics of endemic forest Lepidoptera in the northern hemisphere are population cycles. Characteristics associated with these population cycles are; a periodicity of 6 to 11 years between outbreaks, population increase over 5 to 8 years and then a rapid decline, no period of persistent low population density, and synchronicity among separate populations. For western tent caterpillars epizootics of a viral disease occur in population outbreaks. We propose to study two questions about tent caterpillar population dynamics: Is severity of viral infection in outbreak populations related to environmental conditions, and is the synchronicity of populations among sites environmentally determined or due to dispersal?  We will use newly developed genetic markers to determine to what extent dispersal of moths among populations maintains synchronicity and field experiments and weather and population records to study viral epizootics.In the absence of natural enemies, introduced organisms frequently maintain outbreak densities.  To combat these outbreaks, exotic control agents are introduced. The challenge to population ecologists is to identify the characteristics of biocontrol agents and target weeds that allow control at a lower equilibrium.  The recent dramatic decline of diffuse knapweed, the most serious rangeland weed in British Columbia, following the establishment of a new biological control agent, prompts us to ask "How many insects are necessary for successful biological control?" Parsimony in choosing the types and numbers of biocontrol agents is required for the future safety of this valuable tool for dealing with invasive, exotic pests.  We will use field experiments and observations to determine if a single agent can successfully control knapweed and compare the characteristics of successful to unsuccessful agents.