Symposium: “Partitioning the effects of eco-evolutionary feedbacks on community stability”

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Swati Patel, Michael H. Cortez, and Sebastian J. Schreiber (Mar 2018)

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Natural communities are perpetually subject to disturbances in their environment. Do communities recover from these perturbations or might species be lost? Communities may respond to disturbances in two ways: through an ecological response (species densities may change) and through an evolutionary response (species may adapt to new conditions). Swati Patel, from Tulane University, and co-authors Michael Cortez and Sebastian Schreiber explore how these two responses, in some cases, work together to maintain stable communities, and in others, drive instability that may lead to the loss of species. Using mathematical models, they develop a simple and general formula that predicts whether a community is able to recover or not following an environmental disturbance. Importantly, they find that this depends on how quickly species can evolve relative to how quickly their densities change. Surprisingly, faster evolution does not necessarily imply more stable communities; communities with more rapidly evolving species can actually be more prone to species loss!


Abstract

A fundamental challenge in ecology continues to be identifying mechanisms that stabilize community dynamics. By altering the interactions within a community, eco-evolutionary feedbacks may play a role in community stability. Indeed, recent empirical and theoretical studies demonstrate that these feedbacks can stabilize or destabilize communities, and moreover, that this sometimes depends on the relative rate of ecological to evolutionary processes. So far, theory on how eco-evolutionary feedbacks impact stability exists only for a few special cases. In our work, we develop a general theory for determining the effects of eco-evolutionary feedbacks on stability in communities with an arbitrary number of interacting species and evolving traits for when evolution is slow and fast. We characterize how eco-evolutionary feedbacks lead to stable communities that would otherwise be unstable, and vice versa. Additionally, we show how one can identify the roles of direct and indirect feedbacks between ecological and evolutionary processes on stability, and how the effects of those feedbacks depend on the rate of evolution relative to the ecological time scales. Applying our methods to models of competing species and food chains, we demonstrate how the functional form of trade offs, genetic correlations between traits, and the rate of evolution determine whether eco-evolutionary feedbacks stabilize or destabilize communities.