Species-area curve and spatial pattern

Various models of the relationship between area and number of resident species have been proposed. Most of them either ignore the spatial distribution of the species or suppose that they are spatially distributed at random. A new model is proposed that can deal with any type of spatial pattern, random, regular, or clustered, within the theory of point processes. It only requires that the distribution of the species be spatially homogeneous. The spatial pattern appears to modify the shape of the species-area curve as much as the species-abundance distribution. Mapped locations of trees and shrubs in a semi-arid savanna in Mali illustrate the theoretical developments, and an estimate of the expected number of species in the savanna is given. The observed number of species is consistent with the expected number, provided that the inventoried area remains spatially homogeneous.