Effect of deforestation on a southwest Ghana dung beetle assemblage (Coleoptera : Scarabaeidae) at the periphery of Ankasa conservation area

During June 2003, an exploratory dung beetle survey (Coleoptera: Scarabaeidae: Scarabaeinae) was conducted in southwest Ghana at the southern edge of Ankasa Conservation Area, which is a 500-km(2) conserved region of the threatened Eastern Upper Guinean rainforest. The survey provided a quantitative assessment of peripheral deforestation effects and an inventory for species on omnivore dung. Pitfall traps baited with pig dung were placed in both selectively logged and unlogged rainforest as well as in nearby oil palm and cacao plantations. The Ankasa forest inventory was mostly comprised of species previously trapped by human dung in the Western Upper Guinean rainforest of TO National Park, Cote d'Ivoire. However, there was relatively low species abundance similarity between the June/July assemblages on omnivore dung in Tai and Ankasa rainforests, and even lower similarity between assemblages of Ankasa and the adjacent plantations. Of 29 species recorded in Ankasa forest, most were absent or rare in plantations where assemblages were numerically dominated by species previously recorded from the West African savannas. This replacement plantation fauna showed significantly lower species richness and diversity, but significantly higher abundance, compared with Ankasa forest assemblages. The results reiterate that forest reserves are essential for the conservation of specialist rainforest dung beetle species.