Developing an ecological context for allelopathy

There has been a renewed interest in allelopathy as a plant-plant interaction as more plant ecologists have become involved in studying biological invasions. This resurgence highlights a major deficiency in our understanding of allelopathy-the lack of a well-developed ecological context for the interaction. In contrast to allelopathy, the plant-plant interaction of competition has a strong theoretical foundation as well as a large body of supporting empirical studies. We suggest that the plant-herbivore defense literature provides a mature and well-developed framework from which a broader ecological context for allelopathy can be developed. Here, we discuss three broad classes of questions, drawn from the herbivore defense literature, which may help to develop an appropriate ecological context for allelopathy. These questions focus on (1) variation in allelopathic expression within species, (2) community level variation in allelopathy across species, and (3) variation in the impacts of allelopathy on associated species. Addressing such broad population and community level themes in a variety of systems will be necessary to fully develop an ecological context for allelopathy and provide a theoretical basis for understanding its role in plant communities.