PHENOLOGY OF BUTTERFLIES ALONG AN ALTITUDINAL GRADIENT IN NORTHERN SPAIN

The annual cycle of adult butterflies was studied at seven rocky outcr ops located along an altitudinal gradient in a northern Spanish mounta in area (Picos de Europa) with a Eurosiberian climate in 1993 and 1995 . Both total abundance and number of species of butterflies peaked in summer at all study sites. The cumulative species number uniformly inc reased over the season until late summer. These results imply that but terflies concentrated their activity when temperatures were higher in the year. Regardless of their diversity and total abundance, timing of the flight period was later for assemblages at high altitude than for assemblages at low altitude. A similar trend in increasing delay in f light period was found when data were analysed separately for each spe cies. The duration of the flight period of assemblages was correlated with abundance in 1993, but it was correlated with altitude in 1995. M ost species tended to show shorter flight periods at high altitudes in both study years. These altitudinal changes in timing of adult flight are likely to be linked with effects of temperature on developmental rates of early stages of the life cycle. Changes in duration of the fl ight period, however, might be partly related to variability in specie s abundance.