Island Biogeography: Theory and Applications

† Biological Sciences Center, Desert Research Institute, University of Nevada System, P.O. Box 60220, Reno, NV 89506-0220, U.S.A Island biogeography is the study of pattern in the distribution of species on islands as influenced by ecological and evolutionary processes related to island characteristics such as isolation and area. The MacArthur-Wilson theory of island biogeography asserts that two processes, immigration and extinction, determine the species diversity of an island’s biota. As the number of species on the island increases, the immigration rate decreases and the extinction rate increases. The immigration rate decreases with isolation (distance effect), whereas the extinction rate decreases with island area (area effect). When the immigration and extinction rates are equal, an equilibrium of species diversity is reached. The extinction of species on an island and their replacement by the immigration of new species results in species turnover. The equilibrium theory of island biogeography has been one of the more influential concepts in modern biogeography, ecology, and evolutionary biology. It also has had a major influence on conservation biology, particularly with attempts to develop a theoretical basis for the design of nature reserves. However, several aspects of the theory remain unsubstantiated, and therefore uncritical application of the equilibrium theory of island biogeography to nature conservation is unwarranted.