ANALYSIS OF TEMPORAL SEGREGATION IN A DUNG-INHABITING BEETLE COMMUNITY AT A LOW-ALTITUDE AREA OF THE ITALIAN ALPS

A dung-inhabiting beetle community has been studied at a low-altitude area of an Italian Alpine valley (Pesio valley) by considering the pattern of beetle succession in droppings and their seasonality. As a whole, the community was characterized by a low density of individuals, with coprophagous beetles largely dominant over carnivorous beetles, both with regard to species richness and abundance. Dung beetles showed the lowest values of species richness and diversity during August a time when predatory beetles peaked. It is possible that during the dry season droppings become a refuge habitat for predatory beetles, as a consequence of moisture and prey availability. With regard to core species (abundance equal to or higher than 20), some intergeneric differences were found. Onthophagus species mainly occurred during May and June, whereas Aphodius species were more diversified, with some mainly occurring during May and June, some during September, and others during July. Most species arrived at the pads during the first two-four days. Aphodius species, however, were still arriving after five-six days, whereas Onthophagus species virtually stopped arriving after the third day. These differences between Aphodiidae and Scarabaeidae were not enough to produce any effective temporal resource partitioning. In fact, both Principal Component Analysis and a Cluster Analysis showed that only dominant species and some core species were temporally segregated from the others. Most species largely overlapped both in time of arrival at the dropping and in their seasonal distribution. The low population density suggests that intra- and interspecific competitive interactions were unlikely to occur in the area during the study period. Also, we doubt that past competition should be invoked to explain the few differences observed. That competition may not be a major organizing factor is also indicated by the similar phenologies of the core dweller species all over Europe.