Dispersal in a Metapopulation Neighbourhood Model of an Annual Plant with a Seedbank

A metapopulation neighbourhood model of an annual plant species in a harsh environment is derived. It includes the effects of seed survival, dormancy, competition, dispersal, spatial and temporal heterogeneity, and stochastic local extinctions. In spatially homogeneous and heterogeneous harsh environments with moderate levels of density-dependent competition, all populations persisted and dispersal aided metapopulation growth when the population growth rate was sufficiently large. When the population growth rate was smaller, dispersal increased the risk of, and speeded up the time, to metapopulation extinction. Metapopulation growth was faster when the heterogeneity was at a larger-scale spatial pattern. Temporal heterogeneity had an adverse effect when added to the existing spatial heterogeneity; strongly dispersing metapopulations were affected only slightly, while those with only moderate or no dispersal became extinct. The more frequently the environment changed, the greater was the probability of extinction. Model simulations were repeated for more-severe density-dependence. In the spatially homogeneous environment dispersal prevented metapopulation extinction, while lack of dispersal encouraged it. Dispersal aided metapopulation growth in the spatially heterogeneous unchanging environment. Addition of temporal heterogeneity had little effect on populations with strong dispersal but the effect on the other metapopulations was catastrophic. -from Authors