Synchrony, extinction, and dynamics of spatially segregated, heterogeneous populations

Abstract

Most theoretical assessments of synchrony assume that populations are identical in their ability to produce and absorb dispersing individuals. Relaxing this assumption, I assessed how the local population growth rate, the proportion of individuals dispersing between populations, and different patterns in the immigration rate and carrying capacity with habitat patch size affect synchrony in local population dynamics and metapopulation extinction. All factors influenced both synchrony and extinction, and there were strong interactions between the factors. Local population growth rates had the largest effect on synchrony, followed by the pattern of carrying capacity with patch size and the proportion dispersing. The pattern of immigration with patch size had the smallest effect on synchrony. Metapopulation extinction was largely affected by the population growth rate, with the other factors having smaller but similar effects. Highly synchronous dynamics tended to be associated with greater metapopulation extinction within regions of chaotic local population growth; however, across the range of population growth investigated, high amounts of synchrony did not necessitate extinction. Differences among populations in the ability to absorb individuals mediated by interactions between growth rate, dispersal, patch size, and carrying capacity can substantially affect synchrony and extinction. Not considering how these factors interact may lead to erroneous conclusions regarding synchrony and extinction. Under certain situations, heterogeneity among local populations can promote metapopulation stability despite highly chaotic local dynamics.