Species packing in tropical forests: Diel flight activity of rainforest dung-feeding beetles (Coleoptera : Aphodiidae, Scarabaeidae, Hybosoridae) in Borneo

I describe an activity study in which pitfall and flight intercept traps are used to collect rainforest dung beetles at Danum Valley Field Centre in northern Borneo over five 34 hour periods. Nine hundred and thirty two individuals of 47 species are recorded, from the families Scarabaeidae (subfamily Coprinae and Scarabaeinae), Aphodiidae (subfamily Aphodiinae) and Hybosoridae (subfamily Hybosorinae). There are two peaks in activity, one at mid-night and one at mid-hay, with a very significant difference recorded between the two groups tone-way ANOVA, F = 16.80, df = 8, P < 0.0001), but no statistical difference within the tribes/subfamilies at each peak of flight activity. Results go against an expectation that species differentiation against any resource gradient in tropical rainforest should be complex and lead to multiple guild structures, although I suggest that the examination of more species-rich genera in any group of closely competing individuals may show greater differentiation through time. I conclude that the temporal overlap of many species at the same spatial scale in the rainforests at Danum Valley may be explained by the presence of several functional groups at each focus of activity, which allay inter-specific competition and allow the coexistence of species that show little differentiation from each other through time.