Bimodal seasonal activity of moths and elevation, weather and land use as drivers of their diversity

Moths are an important part of terrestrial insect diversity and contribute substantially to ecosys-tem functioning. Yet, how their activity varies with the season and how different biotic and abiotic factors (elevation, weather, land use) are simultaneously linked to moth community characteristics are still poorly understood. We analysed a vast moth community dataset from Switzerland collected by a single expert across 50 years containing data of 2.8 Mio moth individuals (1,045 species), covering the whole yearly cycle. Using regression models, we related moth community characteristics (total abundance, species richness, biomass) to season, elevation, weather and land use (landscape composition). Moth community characteristics showed a clear bimodal seasonal cycle with an activity peak in early spring and one in summer. The different peaks could be clearly linked to moth species with different overwintering stages, i.e. the spring peak was driven by species overwintering as pupae or adults. Along the elevational gradient, we found increases of all moth community characteristics, levelling of at around 2000 m asl. Also, moth activity increased significantly with increasing temperatures and was higher in landscapes with higher proportions of forests. Based on a moth dataset of unseen extent, we present a well resolved seasonal activity pattern and quantify the role of elevation, landscape composition (forests) and weather (temperature) in driving moth community characteristics. These results will help to better understand variation in moth activity across different temporal and spatial scales and to design targeted conservation efforts, e.g. in lower elevation sites.