Compositional differences between dung beetle (Coleoptera: Scarabaeidae s. str.) assemblages in winter and summer rainfall climates

Scarabaeidae sensu stricto comprise two subfamilies, Scarabaeinae and Coprinae. In scarabaeid assemblages of winter rainfall regions with a short dry season (southern France, southeastern Australia), coprine species greatly outnumber scarabaeines, whereas in winter rainfall regions with a long dry season, there are equal numbers of coprine and scarabaeine species (western Australia, South Africa). In the scarabaeid fauna of the South African winter rainfall region, contrasting compositional trends are shown by the main biogeographical groups. In the predominantly spring-active group, comprising species that are endemic or largely restricted to the winter and bimodal (spring and autumn) rainfall regions, scarabaeine species greatly outnumber coprines. By contrast, in the predominantly summer-active group of species which is widespread in the winter, bimodal and adjacent summer rainfall regions, coprine species greatly outnumber scarabaeines, a pattern characteristic of assemblages in summer rainfall and tropical regions throughout the rest of Africa. The cross-climatic changes in composition of the South African dung beetle fauna result from different responses to climate by the two subfamilies. In the Scarabaeinae, abundance and species richness are largely similar from summer to winter rainfall climates whereas those of Coprinae decline steeply across the same climatic range. These different climatic responses may be related to the lower incidence of warm, moist conditions in the winter rainfall region.