Environmental Variability and the Persistence of Parasitoid–Host Metapopulation Models

Parasitoid–host metapopulation models (after Reeve) were simulated with varying amounts of spatio-temporal or spatial environmental variability, as well as varying dispersal rates and instability of within-population dynamics. Persistence with environmental variability occurred over broad ranges of low dispersal rates, the amount of variability required for persistence increased with increasing dispersal, and the range of values giving persistence was less when within-population dynamics where more unstable. Fixed spatial variation was found to be sometimes more effective than spatio-temporal variability at producing persistence, but with greater variance among replicates. Metapopulations also could persist without environmental variability (as found by Adler), but this occurred at very particular dispersal rates, quite different from those allowing persistence with environmental variability.