Synchrony in Metapopulations at Multiple Time-Scales: Theory, Experiments and Field Data

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This project aims to understand how and why collections of spatially distinct populations of a species (called metapopulations) display synchronous fluctuations in plant and animal numbers. Synchrony among populations has a serious implication for conservation biology. Synchrony means that metapopulations, on occasion, can be simultaneously rare which enhances the likelihood of extinction. Synchrony results from migration among populations and from environmental variation that affects multiple populations. The relative importance of these two mechanisms remains unknown. The current statistical methods of analyzing synchrony have shortcomings. The degree of synchrony between two population time series is usually measured by a single number, such as a correlation coefficient. However, the strength of synchrony between two time series can vary with the time scale on which it is examined, that is, synchrony may have frequency-specific components. To increase our understanding of metapopulation synchrony, this project will (1) analyze data from large spatio-temporal ecological databases, (2) develop new theory and statistical methods, and (3) conduct new laboratory experiments. The implications for climate change, extinction risks, and the mechanisms that drive synchrony (migration and environmental variation) will be assessed. Long spatially-extensive time series of environmental variables and population numbers will be analyzed to characterize the frequency-specific nature of synchrony. Analytical and numerical analyses of mathematical models will develop theoretical expectations for how frequency-specific environmental synchrony affects population synchrony and probabilities of metapopulation extinction. Experiments with laboratory populations of flour beetles will extend earlier studies in several ways. First, the investigators take a time-scale-specific perspective on both environmental and population synchrony. Second, they examine both equilibrium and chaotic populations. Previous theoretical work has show that these two dynamics respond differently to synchronizing processes. Third, their experiments will involve two sibling species of insects whose population dynamics are controlled by different density-dependent mechanisms: cannibalism of immature life stages and delay of metamorphosis. The former leads to rapid responses to perturbations and increases the tendency for demographic cycles whereas the latter leads to slow responses to perturbations and non-cyclic dynamics. The use of both species will allow an evaluation of the generality of the experimental results. This multidisciplinary approach will enhance our understanding of ecological synchrony and its relevance to society.This project will have important practical implications for the effects of global climate change on species extinction and will lead to more sophisticated methods for conserving threatened or endangered species whose populations have become fragmented. The research will capitalize on existing ecological databases and will generate and disseminate high quality laboratory data that can be used to further our understanding of the interactions among environmental variation, dispersal, and population dynamics. The mathematical and statistical tools developed will extend the traditional methods for examining synchrony to consider different time scales and will be applicable to data from other fields. The project will also contribute to the interdisciplinary education of undergraduates and graduate students, including underrepresented groups, and will create and distribute instructional materials to facilitate the use of the flour beetle system for training in quantitative ecology at the undergraduate and graduate levels.