The study of diversity maintenance mechanisms has traditionally focused on competition, with predation mostly seen as modifying what competition does. However, there is growing evidence that predation and competition can have very similar effects on the maintenance of species diversity. This similarity of action relies on the observation by Bob Holt (University of Florida) that both predation and competition can lead to mutually negative indirect interactions between species. Of most importance, such mutually negative indirect interactions apply not just between species but also to different individuals within the same species. Theoretical consequences of these facts mean that predation and competition each have the potential to limit diversity or promote diversity. For both predation and competition it all depends on the extent to which within species interactions outweigh between species interactions. When predation and competition have similar strengths for a given set of interacting species, the overall outcome for diversity maintenance may represent a compromise between the separate tendencies of predation and competition in the given circumstances. In other cases, new mechanisms promoting diversity arise from the interaction between predation and competition. If one mechanism is much stronger than the other, the tendency of the stronger mechanism prevails.
One major thrust within the lab explores these various ideas in general models and in models of specific systems, such as annual plant communities. We combine them with other thrusts on the effects of environmental variation in space and time, and we ask also how trophic cascades affect the maintenance of diversity in any given trophic level.