Scaling of the mean and variance of population dynamics under fluctuating regimes
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Theoretical ecologists have long sought to understand how the persistence of populations depends on the interactions between exogenous (biotic and abiotic) and endogenous (e.g., demographic and genetic) drivers of population dynamics. Recent work focuses on the autocorrelation structure of environmental perturbations and its effects on the persistence of populations. Accurate estimation of extinction times and especially determination of the mechanisms affecting extinction times is important for biodiversity conservation. Here we examine the interaction between environmental fluctuations and the scaling effect of the mean population size with its variance. We investigate how interactions between environmental and demographic stochasticity can affect the mean time to extinction, change optimal patch size dynamics, and how it can alter the often-assumed linear relationship between the census size and the effective population size. The importance of the correlation between environmental and demographic variation depends on the relative importance of the two types of variation. We found the correlation to be important when the two types of variation were approximately equal; however, the importance of the correlation diminishes as one source of variation dominates. The implications of these findings are discussed from a conservation and eco-evolutionary point of view.
KeywordsEnvironmental variability Effective population size Extinction Scaling effect Temporal autocorrelations in the environment
This study has been partly supported by a Marie Curie Transfer of Knowledge Fellowship BIORESC of European Community’s Sixth Framework Programme (contract number MTKD-CT-2005-029957). Furthermore we wish to thank the Aalborg Zoo Conservation Foundation (AZCF) and the Danish Natural Science Research Council for financial support to CP (Grant number: #21-01-0526, #21-03-0125 and 95095995). We thank two anonymous reviewers for invaluable suggestions and help.
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