Figure 3.

Orthogonal niche axes. (A) Circular niches of radius r randomly intersecting a habitat space with orthogonal axes of lengths ar and br. (B) Expected portion of habitat space covered by species increases asymptotically with number of species in the community. One-thousand trials were made for each value, N, of species richness. In each trial, a set of N circular niches of radius 0.218 were randomly placed on a habitat space in which axes ranged from 0 to 1, and the portion of the habitat space covered by this set of N species determined. At least some part of the niche (circle, A) of a species had to intersect the habitat space. •, means of 1000 trials. ·, 100 random trials for each value of N. The solid curve is the theoretical value from Eq. 5. (C) Variance in coverage declines to zero from a peak at intermediate values of species richness.