BIOGEOGHAPHIA — vol. XVI — 1992 (Pubblicato il 31 dicembre 7992) ll popolamento delle Alpi Occidentali Biogeography of dung beetle communities in the western and central Alps (Coleoptera, Scarabaeoidea) ]EAN—PIERRE LUMARETqq and NICOLE ST1ERNETq”q qq Labomtozre dc Zoogeogmplvze — Unizzerrite Paul Vczlery — B.P. 5043, F-34032 Montpe[[z'er Cedex 1 (FI‘£ZIZC€) ”“q Labomtoire de /720172/Jologzie, rysteiimtiqzte at ecologze ti/zzmale - Qzmi mm Belzedeyz, 22, B—4000 Liege (Belgiqz/6) SUMMARY Geographic origin and diversity of the dung beetle fauna \vas studied in two Alpine regions, namely the Vanoise National Park (France) and the Swiss National Park (Grisons) which showed thirty and twenty nine species respectively, with twenty—two species being common. Organisation and dynamics of the dung beetle communities were analysed in upper Maurienne Valley (Vanoise NP and peripheric area). The richness of the fauna was related to the range of climatic conditions and to abundance as well as diversity of the large mammal fauna living there throughout the year. The diversity index decreases as the altitude increases, and the equitability index varies in the same way. All the species assemblages are log-linear types and may be fitted to Motomura’s model. Several core species develop during the favour- able period. In subalpine communities, four successive waves of species replace each other from spring to autumn, whereas, in the highest sites, communities are dominated by a single species which extends its activity throughout the favourable period. 1. INTRODUCTION Mountains are characterized by high rates of insolation and radiation, reduced atmospheric pressure, great diurnal fluctuations in temperature, and low average temperature leading to snow precipitation. Atmospheric aridity increases with elevation because water vapour tension is reduced. Dung bee- tles, which constitute an ecological group of insects whose specific richness and community assemblages influence the functioning of pastures, have to respond to these constraints. Their successive swarming facilitate a rapid use of almost all faeces. Many dung beetle species have been collected in high mountains all over the world, up to 5000 metres in Tibet and the Himalayas (Mani (‘Sc Singh, 1961; Mani, 1968; Stebnicka, 1986, 1989, 1990). Biogeographical data on montane dung beetles, including their altitudinal distributions, have been compiled and discussed by Horion (1950) for the Alps and the Carpathians, and Lumaret and Stiernet (1989, 1991) for the Western and Central Alps. The altitudinal limits of the species above the timber line show many striking differences, depending on the massiveness of the trend lines of the mountain ranges, the topographical peculiarities and chiefly the latitude which controls the climatic conditions and the length of the active period (Lumaret and Stiernet, 1991). 425