Description:

Stability Criteria for Complex Microbial Communities, or the Decline and Fall of Lotka-Volterra.

Abstract:
Pairwise models for species interactions have provided a foundation for understanding the dynamics and equilibria of ecological communities for over 90 years, with a classic example being the generalized Lotka-Volterra equations. These approaches parametrize the direct effect of one population on another, and have been enormously influential. For example, for a large community, theory tells us that if the number of interactions is too large, or their strengths are too high, then we know it won't be possible for all species to stably coexist. If true, this strongly constraints the types and combiantions of interactions we can expect to see in nature. But notably absent from equations like Lotka-Volterra is what mediates these interactions—for example, if two species compete, what are the resources they compete for. This is particularly crucial in microbial communities, where many interactions, both competitive and mutualistic, are mediated by the consumption and production of abiotic resources. Here I describe recent work from our lab demonstrating just how rare it is for direct species interactions to recapitulate the full dynamics of a community of consumers, producers and resources. I also show that those classic results relating to stable coexistence are altered by considering the dynamics of resources, and we find qualitatively new conditions for community stability. Finally, I’ll talk about the prospects for inferring predictive models based on consumers, producers and resources, and the possibility of extensions to more general complex systems.

Short Bio:
PhD Theoretical Physics (University of Cambridge)
Postdoctoral Researcher (University of Oregon)
Omidyar Fellow (Santa Fe Institute)
Assistant Professor, Plant Biology (University of Illinois)