Factors affecting the structure of bee assemblages in extensively and intensively grazed grasslands in Hungary

Abstract

Bees are the most important pollinators in Europe. We studied bee assemblages on 7 pairs of extensively and intensively grazed sites in three lowland grassland types in Hungary. No chemicals were applied on the grasslands. The bees were collected using sweep net surveys and 1 m wide transect surveys in 2003. We mapped land-use types (grasslands; arable fields; forests; built-up areas; marshy habitat and open water) based on aerial photographs within a 500 m radius of each study site. We captured 483 individuals of 124 Apoidea species in total. This shows very diverse and species rich bee assemblages in these semi-natural grassland areas. Both diversity and percentage of rare species were the highest on the Kiskunsag alkali area. The dominance of honey bee (Apis mellifera) was very low at each site. Neither species richness nor abundances differed between extensively and intensively grazed sampling sites, among regions, and between edge and interior of sites. However, both species richness and abundance of bees correlated positively with species richness and cover of flowering plants, indicating the important role of food sources. From the landscape parameters wet areas were preferred by small species, while large species tended to avoid build-up areas.