Abstract: Landscape mosaic induces traveling waves of insect outbreaks
The effect of landscape mosaic on recurrent traveling waves in spatial population dynamics was studied via simulation modeling across a theoretical landscape with varying levels of connectivity. Phase angle analysis was used to identify locations of wave epicenters on patchy landscapes. Simulations of a tri-trophic model with cyclic population dynamics on landscapes with a single focus of high density habitat produced traveling waves generally radiating outwardly from single and multiple foci and spreading to isolated habitat. We proposed two hypotheses for this result, 1) immigration subsidies inflate population growth rates in high connectivity habitat and, thus, reduce the time from valleys to peaks in population cycles, and 2) populations in high connectivity habitat crash from peaks to valleys faster than in isolated habitat due to over-compensatory density dependence. While population growth rates in high connectivity habitat benefited from immigration subsidies, times from population valleys to peaks were greater in high connectivity habitat due to a greater magnitude of fluctuations. Conversely, the mean time of the crash from population peaks to valleys was shorter in high connectivity habitat, supporting the second hypothesis. Results of this study suggest over-compensatory density dependence as an underlying mechanism for recurrent traveling waves originating in high connectivity habitats aggregated around a single focus.
Keywords: connectivity, epicenter hypothesis, larch budmoth, spatial model, synchrony