Rapid Evolutionary Change and the Coexistence of Species

Understanding the forces that allow multiple species to coexist remains a central focus of community ecology. Building evidence that evolutionary changes frequently occur on timescales relevant for ecological dynamics suggests that a complete understanding of the maintenance of diversity is likely to require incorporation of evolutionary dynamics. Coexistence mechanisms can be classified into two groups on the basis of whether they reduce inherent differences in species performance (equalizing effects) or buffer against extinction by providing advantages to rare species (stabilizing effects). Theoretical and empirical evidence suggests that rapid evolution can increase equalizing and/or stabilizing effects in several ways. Directional evolutionary changes can result in new ecological conditions that are more equal or stable than the initial state. Additionally, coevolution between competitors or consumers can lead to cyclic dynamics that provide novel evolutionary equalizing or stabilizing effects.