Migration within Metapopulations: The Impact upon Local Population Dynamics

Publisher Summary This chapter examines the impact of migration within metapopulations upon local population dynamics. A central issue in the analysis of metapopulations is the frequency of migration, or demographic connectivity, among component populations. For most analyses, the actual number of migrants that successfully move between two populations per breeding season or generation is the most important measure of the level of connectivity between them. Migration frequency will be a continuous variable, and may range from zero—where populations are completely isolated from one another—to a value that may be nearly equal to the number of individuals in each unit, in which case the two units function as a single population. This chapter focuses on the more general “rescue effect” metapopulation system, in which migration can prevent local population extinctions, but where there may be stochastic variation in both the rate and the direction of migration. Thus, the identities of the “source” and “sink” populations can change unpredictably through time. The studies discussed in this chapter suggest that metapopulations with strong rescue effects may be more common than currently supposed, and the best way to look for metapopulations with strong rescue effects may be to examine habitat types, rather than particular taxa.