Diurnal Lepidoptera: sensitive indicators of cultivated and abandoned grassland.
Studies were made in the Tavetsch Valley in the subalpine region of central Switzerland, of the day-active Lepidoptera faunas in different types of cultivated grassland, in various stages in the development of abandoned grassland and in woodlands (climax vegetation). The results show a close correlation between the lepidopterous fauna and vegetation type concerning species composition and species richness of Lepidoptera. Species richness of Lepidoptera was highest in early abandoned stages and fell rapidly with the arrival of shrubs and trees. It was also high in traditionally lightly cultivated grassland (unfertilized mown and lightly grazed meadows), but it declined drastically with increasing intensity of cultivation. In general, species richness of Lepidoptera was closely correlated with species richness of vascular plants, but cultivation methods and the short time since abandonment (<5 years) of lightly cultivated grassland had strongly different influences on species richness of Lepidoptera and vascular plants. The results are in contrast to former studies in Central Europe and parallel studies in England. The natural primary habitats of Lepidoptera living in the anthropogenetic types of vegetation investigated and the consequences for nature conservation are discussed.