Influence of dense stands of an exotic tree, Prosopis glandulosa Benson, on a savanna dung beetle (Coleoptera: Scarabaeinae) assemblage in southern Africa

In the savanna biome of southern Africa, introduced mesquite species have transformed at least 200,000 ha in the northern Cape Province of South Africa and could have a significant effect on insect diversity in this biome. The effect of a dense Prosopis glandulosa stand on a savanna dung beetle assemblage was investigated over a 16-month period using pitfall traps baited with cattle dung. A total of 41 species was recorded in the undisturbed savanna compared to 34 in the thicket. In addition, the two habitats differed in the biomass, numbers, dominance, diversity, equitability and size distribution of the species. Larger dung beetles (>30 mg dry weight), particularly telecoprids, showed a marked aversion to the Prosopis thicket, while they comprised 60% of the assemblage in the open savanna. Rare species in the assemblage from undisturbed savanna all showed a marked decline in the Prosopis thicket. It is argued that greater attention should be given to land management practices in arid savanna regions where bush encroachment is likely.