Spatial Dynamics of Seed Predators on Synchronized and Intermittent Seed Production of Host Plants

American Naturalist (2004) 163:591-605

Abstract

Masting, the synchronized and intermittent seed production by plant populations, provides highly variable food resource for seed predators, which can minimize losses to the predators through satiation and extinction of local seed predator populations. Specialist seed predators, in turn, counter against masting through dispersal or extended diapause. We developed a resource-consumer model to understand ecological consequences of the interaction between masting plants and specialist seed predators. Masting dynamics is quantified by a resource-based model for plant reproduction. The dynamics of the predator is assumed to follow a spatially-extended Nicholson-Bailey model. The resultant model shows that when host plants show intermittent reproduction, seed predator populations go locally extinct, but global persistence of the predator can be ensured due to dispersal to adjacent plants. Global extinction of the predator results when intermittent reproduction is highly synchronized among plants. An approximate invasion criterion for the predators shows that negative lag-1 auto- and cross-correlation in seeding prevent invasibility of the predators. Spatial synchrony in seeding at local scale due to pollen coupling (or climate forcing) further prevents invasion of the predators. If the predators employ extended diapause, extremely high variability in reproduction across years is required for plants to evade the predators.

Key words: masting, synchrony, dispersal, spatial dynamics, predator satiation, invasibility.