On Species-Area Relations

Species-area relationships have been of interest in ecology for a long time (de Candolle 1855; Jaccard 1902, 1908). They have been called "one of community ecology's few genuine laws" (Schoener 1976, p. 629). Plotting number of species (S) against sampling area (A), for a series of samples of increasing sizes, yields a monotonically increasing curve whose slope is steep at first but gradually becomes nearly flat. The shape of such curves has been used to help determine the area required to obtain an adequate sampling of the species in a particular community-the "minimal area" concept (Goodall 1952; Hopkins 1957; Cain and Castro 1959; Barkman 1989), to characterize community structure (Fisher et al. 1943; Goodall 1952; Preston 1962; May 1975), to estimate species richness (Evans et al. 1955; Kilburn 1966; Hubbell and Foster 1983; Palmer 1990; Baltanas 1992; Grassle and Maciolek 1992), to measure the effect of disturbance on communities (Lawrey 1991), and to define the appropriate size of reserves and natural areas in conservation biology (MacArthur and Wilson 1967; Soule et al. 1979; Williamson 1981). A large number of natural comimunities have been investigated, especially by plant ecologists. They found that different communities may exhibit different types of species-area relations. Among them, three expressions are most widely used: exponential curve (Gleason 1922, 1925),