Patterns of Butterfly Diversity Above the Timberline in the Italian Alps and Apennines

The Italian butterfly fauna comprises 275 native species (Balletto et al. 1995), of which 106 occur in the Italian Alps (25 strictly alpine) and 64 in the Apennines (10 alpine). They form loose assemblages, apparently exhibiting low inter-specific competition for either space or other resources (Gilbert and Singer 1973; Gilbert 1984; Balletto et al. 1985; Porter et al. 1992). Density-independent processes (Den Boer 1998) generally determine their population sizes. The assemblages are made up of various combinations of stenotopic species (characterised along gradients) and broadly eurychorous or, sometimes, migratory species. Strict stenotopy, where it occurs, is generally a consequence of adult behaviour rather than of larval biology; the genus Maculinea (see Thomas 1994 for a review) affords a rare example in Europe. Even rarer are cases where stenotopy derives from strict larval monophagy, such as that observed for some species feeding on Vaccinium, or on some leguminous plants (Balletto et al. 1985, and literature cited therein).