Diversity-Dependence, Ecological Speciation, and the Role of Competition in Macroevolution

Variation in the rate of species diversification underlies many large-scale patterns in the organization of biological diversity. Here, I explore the phenomenon of diversity-dependent diversification and its contribution to differential species proliferation in time and space. Diversity-dependence can be a pattern of asymptotic diversity change through time as well as a process by which interspecific competition influences the dynamics of speciation and extinction. I review the evidence for diversity-dependence as revealed by phylogenies and fossils and discuss the close relationship between diversity-dependence and Darwin's proposed mechanism for the origin of species. An emerging body of research suggests that diversity-dependence contributes to the formation and persistence of incipient species and raises new questions about the meaning of ecological speciation. Diversity-dependence provides a conceptual framework for unifying biodiversity patterns across scales that vary by many orders of magnitude, from the dynamics of geographic range evolution to speciation and adaptive radiation.