Regional species coexistence despite local priority effects: the overlooked role of dispersal-community feedback

Abstract

Many cases of animal-mediated dispersal are non-random, with the animals altering their movement pattern in response to the local species composition of the organisms that the vectoring animals disperse. Yet, this dispersal-community feedback has received little attention in metacommunity ecology. We use a mathematical model to show that dispersal-community feedback can promote regional species coexistence. As a well-characterized system, our model focuses on nectar-inhabiting bacteria and yeast that are dispersed by pollinators and affected by priority effects within flowers once dispersed. Model analysis suggests that bacteria and yeast coexist regionally across a wide range of regional pollinator abundances only when their occurrence in flowers influences the frequency of flower visits by pollinators. This microbe-pollinator feedback creates positive frequency dependence in each plant, causing competitive exclusion at the plant scale, but spatial partitioning across multiple plants, stabilizing coexistence at this scale. Our finding highlights dispersal-community feedback as an overlooked potential contributor to species coexistence.