The relationship between area and species number on islands, as an equilibrium between immigration and extinction. See R. H. MacArthur and E. O. Wilson (1967) and R. Whittaker (1998).

Island biogeography is also relevant to continents, when plant and animal communities are effectively reduced to islands in a sea of cultivation or urbanization; Meadows (2001) PPG 25, 1 writes on habitat islands—distinctive communities in a sea of other types of community.