Abstract
The number of species of terrestrial vertebrate in one of the world's great zoological regions fits a linear combination of area (A) and one climatic variable-either annual actual evapotranspiration (AE) or mean annual temperature (T)-with an R 2 of 0.97. The same is true of species diversity in the four separate classes of terrestrial vertebrate; their R 2-values range from 0.90 to 0.95.