how important is biodiversity relative to other factors that influence ecosystem functioning?
Both our understanding of the effects of biodiversity on ecosystem processes, and the effectiveness of alternative strategies for the preservation of biodiversity, are limited by our knowledge of the mechanisms that maintain diversity. The mechanisms most relevant to ecosystem functioning are those that maintain diversity on the local scales within which individuals of one species interact with individuals of other species. It is from such interactions among individuals of different species that diversity is expected to impact ecosystem processes. What are these mechanisms of coexistence? At present there are an abundance of alternative hypotheses but no clear demonstrations of the actual processes that maintain the diversity of species-rich ecosystems. In a general sense, coexistence requires the existence of evolutionarily persistent interspecific trade-offs in the abilities of species to deal with the factors that constrain their fitness and abundance. However, there are many potent
