Habitat heterogeneity, environmental feedbacks, and species coexistence across timescales

Abstract

A large body of ecological theory explains the coexistence of multiple species in variable environments. While spatial variation is often treated as an intrinsic feature of a landscape, it may be shaped and even generated by the resident community. All species modify their local environment to some extent, driving changes that can feed back to affect the composition and coexistence of the community, potentially over timescales very different from population dynamics. We introduce a simple, nested modeling framework that describes species coexistence in heterogeneous environments, as well as the evolution of this heterogeneity over time due to feedbacks from the biotic community. We derive analytical conditions for the coexistence of any number of species in environments with intrinsic heterogeneity or feedbacks, and identify essential differences between these scenarios. Our model is naturally simplified in the limit of very fast or very slow environmental feedbacks, allowing us to treat these two scenarios - which bookend the full range of dynamics - in detail. Among other results, we demonstrate how dispersal and environmental specialization interact to shape realized patterns of habitat association. We also show that environmental feedbacks can tune landscape conditions to promote stable coexistence, although feedbacks can give rise to complex dynamics such as limit cycles, priority effects, and episodic dynamics, as well. Our flexible modeling framework helps explain how and when each of these behaviors arise, and offers a generic mathematical platform for exploring the interplay between species and landscape diversity.