Environmental Correlates of Patterns of Species Richness in the South-Western Cape Province of South Africa

The patterns of species richness in the south- western Cape Province, South Africa, at a quarter-degree scale are documented for several plant taxa typical of the Cape flora, i.e. Restionaceae, Ericaceae, Proteaceae, Penta- schistis (Nees) Stapf (Poaceae) and Aspalathus L. (Faba- ceae). The patterns of species richness are very similar for all taxa investigated. These patterns are correlated to a range of environmental factors: precipitation, altitude, substratum and vegetation type. It is shown that total precipitation is the best predictor for the patterns of species richness, but that this is to some extent correlated with the range of precipita- tion and the altitude range. To test for the effect of individ- ual factors, selected samples in which one environment factor varied, were compared. This clearly showed that rainfall is the best predictor. The number of substrate types, curiously, is not strongly correlated to the patterns of species richness.