Occupancy, spatial variance, and the abundance of species.

where a and b are constants. Indeed, such models can be used at a spectrum of spatial scales to describe spatial variance in the abundance of a single species at different times or in different regions and of different species across the same set of areas (Taylor et al. 1978; Taylor and Woiwod 1982). A second general pattern that has come to prominence more recently is that the proportion of areas occupied by a species (p, its probability of occurrence in a sample) increases with its average abundance (m) among those areas and again that this is manifest from microto macrospatial scales both for a given species at different times or in different regions and for different species across the same set of areas (Brown 1984; Gaston and Blackburn 2000). While a number of models have been developed to describe this pattern, most are special forms of the general model (Wright 1991; Hanski et al. 1993; He and Gaston 2000)