The population component of a species' niche corresponds to the distribution of individuals
across environments within a region. As evolutionary clades of species diversify, they
presumably fill niche space, and, consequently, the rate of increase in species numbers
slows. Total niche space and species numbers appear to be relatively stable over long
periods, and so an increase in the species richness of one clade must be balanced by
decrease in others. However, in several analyses, the total population niche space occupied …