The emergence and maintenance of diversity: insights from experimental bacterial populations

Mechanisms maintaining genetic and phenotypic variation in natural populati ons are central issues in ecology and evolution. However, the long generati on times of most organisms and the complexity of natural environments have made elucidation of ecological and evolutionary mechanisms difficult. Exper iments using bacterial populations propagated in controlled environments re duce ecosystem complexity to the point where understanding simple processes in isolation becomes possible. Recent studies reveal the circumstances and mechanisms that promote the emergence of stable polymorphisms.