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 pat tern of beetle succession in droppings and their seasonality. As a who le, the community was characterized by a low density of individuals, w ith coprophagous beetles largely dominant over carnivorous beetles, bo th with regard to species richness and abundance. Dung beetles showed the lowest values of species richness and diversity during August a ti me when predatory beetles peaked. It is possible that during the dry s eason droppings become a refuge habitat for predatory beetles, as a co nsequence of moisture and prey availability. With regard to core speci es (abundance equal to or higher than 20), some intergeneric differenc es were found. Onthophagus species mainly occurred during May and June , whereas Aphodius species were more diversified, with some mainly occ urring during May and June, some during September, and others during J uly. Most species arrived at the pads during the first two-four days. Aphodius species, however, were still arriving after five-six days, wh ereas Onthophagus species virtually stopped arriving after the third d ay. These differences between Aphodiidae and Scarabaeidae were not eno ugh to produce any effective temporal resource partitioning. In fact, both Principal Component Analysis and a Cluster Analysis showed that o nly dominant species and some core species were temporally segregated from the others. Most species largely overlapped both in time of arriv al at the dropping and in their seasonal distribution. The low populat ion density suggests that intra- and interspecific competitive interac tions 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 f actor is also indicated by the similar phenologies of the core dweller species all over Europe.