THE EFFECTS OF LARGE-SCALE AND SMALL-SCALE RANDOM EVENTS ON THE SYNCHRONY OF METAPOPULATION DYNAMICS - A THEORETICAL-ANALYSIS

We present an analysis of the conditions under which migration and glo bal random factors may determine large-scale synchrony in the dynamics of spatially structured populations. We derive an analytic approximat ion which describes how the desynchronizing influence of local environ mental stochasticity combines with the synchronizing influences of lar ger-scale environmental stochastic variation and migration to determin e population cross-correlation coefficients. Despite the simplificatio ns made by this analysis, computer simulations show that the behaviour of more complicated models is well described by our approximation ove r considerable regions of parameter space. We conclude that population synchrony is largely determined by the coefficients of variation (CVs ) of the local-and larger-scale stochastic processes, and that migrati on alone is only likely to maintain population synchrony when the CV o f the local stochastic process is very small.