Habitat fragmentation in southern Africa and distributional response patterns in five specialist or generalist dung beetle families (Coleoptera)

Effects of habitat fragmentation on spatial distribution patterns of dung beetles were studied in the southwestern Cape in the winter rainfall region of South Africa, where indigenous shrubland has been extensively replaced with crops and pastures. The six most abundant higher taxa of dung beetles showed a range from higher to low discrimination in response to spatial variables based on the results for principal components analysis (PCA) (Scarabaeidae, Aphodiidae, Histeridae, Staphylinidae: predatory subfamilies, Hydrophilidae, Staphylinidae: Oxytelinae). Vegetation type was the principal determinant of spatial distribution whereas annual temperature and rainfall were of much lesser importance. Across the taxonomic sequence from higher to low spatial discrimination, there was a trend from higher to lower proportions of indigenous shrubland specialists. This taxonomic sequence to decreasing spatial discrimination was also related to increasing percentage taxonomic similarity between species assemblages of the higher taxa in the southwestern Cape and those in the distant Transvaal, summer rainfall region PCA (variance) reflected this relationship between local and subcontinental scales of spatial distribution better than a generalization/specialization index (niche width). Species which were widespread on a subcontinental scale (n=25), showed greater pasture associations in the southwestern Cape than in the Transvaal. These trends in spatial distribution patterns indicate that, in response to habitat fragmentation, there has been proportionally greater, recent recruitment of species into southwestern Cape assemblages from spatially less discriminating higher taxa than from spatially more discriminating taxa.