Casey terHorst

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  Rapid Evolution of Multiple Species Increases Coexistence: Insights from Models and Model Systems
  Casey terHorst

  Niche theory tells us that in order for multiple species to coexist sustainably, they must evolve traits such that they diverge to use distinct niches. The neutral theory of biodiversity suggests that although similar species cannot coexist indefinitely, they can co-occur for hundreds to thousands of generations. Given that rapid evolution on ecological time scales can affect interactions between species and the outcome of competition, should we expect competitors to converge or diverge in their resource use? We simulated eco-evolutionary competitive dynamics and found that both convergence and divergence are both viable evolutionary strategies. Evolutionary and competitive outcomes depend on: (1) the rate of evolution relative to the rate of competitive exclusion, (2) the initial similarity of any two species of interest, and (3) whether evolution occurs in a community context, where indirect effects play a role in trait evolution. We are now attempting to test predictions from this model in controlled laboratory experiments with competing species of protozoa. Rapid evolution in a community context is increasingly being incorporated into both theoretical and empirical studies and is critical for understanding eco-evolutionary dynamics in complex communities