Quantifying habitat-specific contributions to insect diversity in agricultural mosaic landscapes

1. Agricultural intensification often leads to loss and fragmentation of natural and semi-natural habitats. As a consequence, biodiversity in intensively managed agro-ecosystems is often lower than in agricultural landscapes with greater natural and semi-natural land cover. Different types of semi-natural habitat may support specific species assemblages thereby increasing landscape-level biodiversity, but this has seldom been tested, especially for insects that have different functional roles in agro-ecosystems. 2. Here, we quantified these habitat-specific contributions by surveying species richness and composition of wild bees, true bugs and ground beetles and compared them among different types of semi-natural habitats within two differently structured agricultural landscapes in Switzerland. 3. We found high shares of habitat specific species and habitat types within landscapes to differ up to fourfold in their specificity (i.e. their contribution to the total landscape species richness). Using statistical null models for habitat specificity and multiplicative beta diversity, we identified habitats that contributed more or less than expected by chance to the overall species diversity at the landscape level. 4. The observed degree of complementarity among habitats highlights the importance of habitat diversity for insect species richness and potentially ecosystem functioning in agricultural landscapes. By helping to understand better the habitat-specific contributions to insect diversity in agricultural areas, our results will facilitate targeted conservation measures and sustainable landscape planning. Yet, qualitative differences in habitat specificity and separation of habitat-specific communities observed between landscapes should be explored further in future studies of multiple landscapes.