A Spatially Explicit Model of Mutualism

Abstract

Mutualistic interactions are robust biological systems with unique population dynamics that result in the observed occurrences of numerous interacting populations. Theoretical models in the literature explain the population dynamics of species involved in mutualisms in terms of positive and negative density-dependent and density-independent factors. Historically, few models have included explicit space in the form of discrete habitat patches to explore how the population dynamics of mutualistic species contribute to patterns of mutualism persistence affected by factors including dispersal and changes in habitat quality. We develop mathematical models to describe population dynamics of two mutualist species across a two-patch network to analyze the effects of explicit space, habitat quality and species-specific colonization rates on persistence of a mutualist community. Immigration and emigration can each mitigate the effects of decreasing patch quality, with low levels of colonization into a poor patch and greater emigration from a poor patch allowing persistence across the greatest range of habitat qualities. Within a plant-pollinator framework, the stability of the mutualism was more sensitive to decreasing patch quality for the pollinator than equal decreases in plant-specific patch quality.