Johannes Schnepf

PDF der Diplomarbeit im Hochschulschriften-Service der Universität Wien

Diversity of diurnal Lepidoptera across an elevational gradient above the timberline

Only few empirical studies described changes of species richness and composition, and the complex interplay of environmental predictors and Lepidoptera distribution patterns, across altitudinal gradients in the Alps. This study focuses on the altitudinal distribution of diurnal Lepidoptera above the timberline on Mount Schrankogel (3,497m) in the Stubaier Alps (Tyrol/Austria). Diurnal Lepidoptera assemblages were surveyed in June and July 2009 along 25 horizontal line transects of 100m length, covering an elevational gradient between 2,050 and 3,200 m asl. A total number of 75 diurnal Lepidoptera species (1,087 sightings) belonging to 15 families were recorded. Lepidoptera species richness and abundance decreased continuously with increasing altitude, decreasing plant richness, nectar availability and vegetation cover. Lepidoptera species composition changed continuously across the elevational gradient resulting in a proportionally higher dissimilarity of species assemblages at larger altitudinal distances between transects. Furthermore, species richness of Lepidoptera decreased in similar ways towards higher altitudes independently if only species with monophagous, oligophagous or polyphagous larvae were considered. These results are consistent with the expectation of a continuous ecotone connecting alpine to subnival habitats, and do not support the idea of sharply defined biotic zones. A long-term monitoring scheme should be implemented to quantify potential upward shifts of altitudinal distribution of alpine Lepidoptera species reflecting a response to the already documented upward migration of plant species corresponding to climate change.