Endogenous spatial heterogeneity in a multi-patch predator-prey system: insights from a field-parameterized model

The causes and consequences of spatial heterogeneity in population dynamics are of both theoretical and practical interest. Previously, we described (Kummel et al., Oikos 122:896–906, 2013) a field system in which predation by ladybugs drives the development of strong spatial heterogeneity among aphid populations living on nearby plants. In this paper, we investigate the detailed mechanisms responsible for this phenomenon. We develop a detailed mathematical model of the system, parameterized by an extensive experimental work showing that ladybugs tend to remain on plants with high aphid numbers and are attracted to plants on which ladybugs are actively feeding. The model reproduces important aspects of the field system and allows us to explore how various behavioral features contribute to these dynamics. The results indicate that spatial heterogeneity results from the random aspect of ladybug foraging that causes some large aphid populations to be under-exploited. For parameter values that are unrealistic for our system, the model displays other types of complex dynamics, including predator swarming and chaos. Our study illustrates how a realistic, carefully parameterized model can connect individual behavior to larger scale spatiotemporal dynamics.