Demographic and environmental stochasticity in predator-prey metapopulation dynamics

1. We studied the metapopulation dynamics and persistence of an extinction-prone predator-prey interaction. We show that the dynamics of the system are influenced by both stochastic and deterministic processes. 2. Using host-parasitoid metapopulation data, we develop appropriate descriptors of the local within-patch population dynamics. In particular, we show that the local dynamics are well described by a Markov chain. We show that the local dynamics are determined predominately by demographic stochastic processes and that the deterministic signal is relatively weak. 3. To test the hypothesis that the persistence of predator-prey metapopulations is affected by habitat size, local population dynamics and different types of (demographic or environmental) stochasticity, we fit population models to the regional metapopulation time-series. Contrary to expectations this demographic noise is, however, undetectable at the regional scale and is masked by an environmental noise process. We show that by linking patches together, the predicted environmental noise is effectively decreased as metapopulation size increases. 4. Using a simple spatial stochastic model, we illustrate that the effects of demographic noise are masked rapidly at the regional scale due to the statistical effects of the central limit theorem. We discuss the implications of this for understanding the dynamics and persistence of metapopulations.