Spatio-Temporal Mosaics in Cycling Populations: The Role of Species Interactions

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There is considerable interest in the apparent increase in spatio-temporal variability in population dynamics, including changes in population size, cyclic propensity, and geographic distribution of a number of free-ranging insects, birds, and mammals. Climate change and other broad-scale stressors have been blamed for such phenomena, but to date a mechanistic framework for the role of species interactions has not been given careful scrutiny. The research program will resolve outstanding questions related to the role of species interactions in cyclic attenuation and geographic range loss. First, in a southern population of Canada lynx, we will evaluate the role of agonistic competition (i.e. strife) on lynx behaviour via monitoring spatial displacement via GPS telemetry of the predator guild (lynx, coyote, bobcat). The exploitative competition (i.e., food) hypothesis will be examined by conducting stable isotope analysis for the 3 carnivores across their range, and examining the extent of dietary overlap according to prey availability and carnivore levels of sympatry. Second, snowshoe hare responses to perceived predation risk will be examined via a field experiment altering such risk in the core and periphery of their distribution and documenting behavioural, physiological, and demographic responses. The direct and indirect role of predation on hare population cycles, including through interaction with climate, will be assessed via population models. Third, we will compare contemporary methods of population analysis to determine which is most sensitive to detecting cyclicity and cyclic attenuation in ecological datasets, and then examine the prevalence of these dynamical properties using the Global Population Dynamics Database. Fourth, we will explicitly test the role of competition and predation risk on cyclic dynamics by conducting experiments using a rotifer-alga (predator-prey) system that allows us to infer population-level responses. Thus, collectively this program will provide comprehensive insight into the role of species interactions on patterns of population change, and thereby help us better understand why many natural populations seem to be undergoing dynamical variability.