Biodiversity and Conservation 9: 683–705, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands. The relationship between local and regional diversity of indigenous forest fauna in KwaZulu-Natal Province, South Africa MICHAEL J. LAWES ∗ , HARRIET A.C. EELEY and STEVEN E. PIPER Forest Biodiversity Programme, School of Botany and Zoology, University of Natal (Pietermaritzburg), Private Bag X01, Scottsville 3209, South Africa; *Author for correspondence (fax: +27-(0)33-2605105; e-mail: Lawes@zoology.unp.ac.za) Received 16 March 1999; accepted in revised form 15 September 1999 Abstract. 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 repres- ent 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, suggest- ing 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 speci- ation, 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. Key words: community saturation, pool exhaustion, regional enrichment, species interaction, species richness Introduction Although representing only 0.27% of the total land surface area (Rutherford and Westfall 1994) indigenous forest in South Africa is characterised by rich local and regional faunal assemblages (Geldenhuys and MacDevette 1989). No other southern African biome remotely approaches the density of reproducing species found in forest (Siegfried 1989). However, indigenous forest is poorly managed and largely ignored in South Africa and is suffering increasing anthropogenic disturbance (Castley and Kerley 1996). Part of the difficulty of managing and conserving forests is that the processes that determine their community structure are poorly understood. In the past explanations for differences in local diversity have depended on the traditional view that physical conditions, and their influence on local interactions among species, limit the number of coexisting species in communities (for reviews see MacArthur and