The relationship between local and regional diversity of indigenous forest fauna in KwaZulu-Natal Province, South Africa

The relationship between local and regional diversity was tested by regressing local community richness against regional species diversity for three taxa, birds, butterflies and mammals, in subtropical forest. The quadratic model best fits the relationship between local and regional diversity for birds. Local bird species richness is theoretically independent of the size of the regional pool of species and may represent saturated communities. A linear model best describes the relationship for mammals and butterflies. For mammals, the slope is shallow (0.264) and regional richness overestimates local species richness, suggesting communities are undersaturated. Extinction filtering may explain this pattern. Past climatic changes have filtered out many mammalian species, these changes have been too recent for autochthanous speciation, and the relatively low vagility of mammals has prevented extensive recolonisation. Differences in the nature of the diversity relationship between taxa are as much due to independent evolutionary histories as to differences in vagility and colonising potential. A pervasive role is suggested for regional biogeographic processes in the development of faunal assemblage structure. Large-scale processes are not considered in current conservation plans. We encourage the shift of conservation emphasis from local ecological processes and species interactions, to whole communities and consideration of regional processes.