I review the mathematical and biological aspects of Hubbell's (2001) neutral theory of
species abundance for ecological communities, and clarify its historical connections with
closely related approaches in population genetics. A selective overview of the empirical
evidence for and against this theory is provided, with a special emphasis on tropical plant
communities. The neutral theory predicts many of the basic patterns of biodiversity,
confirming its heuristic power. The strict assumption of equivalence that defines neutrality …