Bee – Plant networks in agricultural landscapes are enhanced by increased landscape diversity and agri-environmental measures

This is the authors' abstract. We don't add key points for this paper.

Wild bees are among the most important insect pollinators, but their abundance and species richness are declining due to various interacting factors. Many of them are related to land-use change and agricultural intensification. Agri-environmental measures to promote (wild) bee species richness and abundance in agro-ecosystems, aim to support organic farming practices, landscape diversity and floral resources. Analyses of bee-plant network characteristics allow a more in-depth assessment of the effectiveness of agri-environmental measures. In the present study we assess the network diversity, specialization and niche overlap of bees in bee-plant networks in a central European farmland in comparison to landscape diversity, organic farming and floral resources. Networks were surveyed in 100 test areas (625 ×625 m) on 10 randomly chosen transect-crosses per test area. Landscape diversity was assessed by habitat mapping and subsequent calculation of the Shannon Landscape Diversity Index (LSDI) and the proportion of semi-natural habitats (SNH) per test area. The proportion of organic farming and of biodiversity areas according to the Austrian agri-environmental scheme (2015–2022) per test area were calculated to assess their efficiency for network metrics. Forage availability was studied by average flower cover estimated in categories and plant richness was documented per test area. Finally, 28 test areas, with sufficient interaction data to calculate reliable network metrics, were used for detailed statistical analysis. While niche overlap of bees was not significantly related to any of our explanatory variables, network diversity was significantly enhanced by increasing LSDI, proportions of SNH and biodiversity areas. Network specialization showed a trend to benefit from increased proportions of organic farming, but network metrics were not related to flower cover. The results suggest that increasing flower cover is not sufficient to accomplish niche complementarity of bee-plant networks. We highlight the utmost importance of high landscape complexity to maintain resilient bee communities and ultimately increase biodiversity in agro-ecosystems.