Management pressure drives leafhopper communities in vineyards in Southern Switzerland

1. The effects of the current changes in traditional agricultural practices in the Alps on the biodiversity affecting ecosystem functions and services are little known. Vineyards are among the oldest anthropogenic environments of high cultural and natural value that shape the landscape of large areas in Central and Southern Europe. In several mountain regions of the Alps, vineyards are a valid alternative to the landscape homogenisation that has followed post-cultural land abandonment and agriculture intensification. Key unanswered questions remain regarding the relative contribution of several factors that influence biodiversity, and the level in management pressure with regard to taxonomic and functional diversity enhancement. 2. To answer these questions, we sampled leafhoppers (Auchenorrhyncha) as a model taxon using different standard techniques along 24 vine transects within 8 vineyard complexes in Southern Switzerland. Each transect included one vine row, vine canopy, its interrow and the adjacent slope; the latter two were permanently grass-covered. Data were analysed using a four-step approach. 3. Environment (five variables) and Management (four variables) accounted for most of the variance in the leafhopper assemblage. Pesticide use (insecticide and herbicide) and slope mowing are the most important management predictors of leafhopper species composition. 4. With increasing management pressure (i.e. pesticide and mowing), the number of indicator species and particularly the specialists (i.e. stenotopic and oligotopic species) decreases dramatically. 5. To promote taxonomic and functional complexity of communities in vineyard systems, we suggest low management pressure with moderate use of pesticide and a low intensity regime of slope mowing.