Background/Question/Methods Why are there so many different species of trees in the forest? Given a single environment, it seems that one species or strategy should dominate, but species coexistence is much more common than dominance by a single strategy. Why do trees have different traits that allow them to coexist? In ecological succession, physiological constraints prevent a single species from dominating at all times. Different strategies dominate at each successional stage, and succession is reset by disturbances. In a metacommunity composed of multiple patches, random disturbances allow patches to vary in age and successional stage, which can allow multiple strategies to coexist at any given time. However, the generation of differences in strategies that allow for this coexistence remain a mystery. Can successional dynamics in a stochastic metacommunity produce evolutionarily stable coexistence, where two or more strategies cannot be outcompeted by another strategy that is introduced to the environment? Results/Conclusions We develop an individual-based metacommunity model with stochastic disturbances to determine if successional dynamics can cause tree diversification. We incorporate realistic forest gap dynamics by simulating individual-based competition for light. We show that a tradeoff between canopy and understory growth rates can produce successional dynamics in a single patch. In the metacommunity of patches, when patch disturbance frequency is high, individuals spend more time in full sunlight, and strategies that maximize canopy growth rates dominate. When disturbance frequency is low, patches persist long enough for the canopy to close, more individuals spend time in the shade, and strategies that maximize understory growth rates dominate. Intermediate disturbance frequencies have the greatest potential to promote stable coexistence. We use evolutionary game theory to show which strategies are evolutionarily stable in a given environment, and present new methods for calculating fitness of rare mutant strategies in stochastic metacommunities with realistic forest dynamics.
