COS 211-6 - Connecting local and regional scales with stochastic metacommunity models: competition, ecological drift, and dispersal

Abstract: Despite the well-known scale-dependency of ecological interactions, relatively little attention has been paid to understanding the dynamic interplay between various spatial scales. This is especially notable in metacommunity theory, where births and deaths dominate dynamics within patches (the local scale), and dispersal and environmental stochasticity dominate dynamics between patches (the regional scale). By considering the interplay of local and regional scales in metacommunities, the fundamental processes of community ecology — selection, drift, and dispersal — can be unified into a single theoretical framework. Here, we build and analyze a stochastic spatial model of competitive metacommunities that allows feedbacks between local and regional scales and captures the well-studied metacommunity paradigms as special cases. We show that local outcomes do not necessarily translate to the same regional outcomes, with examples of local coexistence and local founder-control both resulting in competitive exclusion at the regional scale. Feedbacks between the local and regional scales are crucial for understanding how regional exclusion can occur without local exclusion. We find that regional coexistence always implies local coexistence, unless environmental disturbances permit a competition-colonization or successional-niche trade-off. Broadly, our model provides a unifying framework for understanding how selection, drift, and dispersal jointly shape ecological communities.