From Niches to Distributions
This chapter explores the conceptual bases for the discrepancy between species’ potential geographic distributional areas and their occupied distributional areas, focusing on the case of conditions when the Eltonian Noise Hypothesis is true as well as the necessary modifications when it is not. It first considers the meaning of the potential distributional area and the reasons why an ecological niche model may not estimate it correctly. It then explains why a species may not be at equilibrium with its potential distributional area, but rather inhabits only some subset of areas suitable for it. It also discusses nonequilibrium distributions that may arise in terms of the BAM diagram before concluding with an analysis of procedures for further processing of a niche model, which expresses potential geographic distributional area, to yield an estimate of occupied distributional area.