1 Department of Biological Sciences, Genetics and Ecology, Faculty of Science, Aarhus University, Aarhus University2 Department of Bioscience - Plant and Insect Ecology, Department of Bioscience, Science and Technology, Aarhus University3 Department of Bioscience - Plant and Insect Ecology, Department of Bioscience, Science and Technology, Aarhus University
Red clover is a key floral ressource for bumblebees (Bombus spp.).We here investigate variation within and among red clover fields in species richness and abundance of Bombus spp. in addition to Apis mellifera. Bumblebee individuals were grouped into the following functional groups, based on castes and tongue length: (1) all queens, (2) all workers, (3) short-tongued workers and (4) long-tongued workers. In 14 study fields, no spatial or diurnal within-field differences were found in abundances of bee groups. However, seasonal differences were detected. On average 6.3±0.6 Bombus spp. were observed in each field. In general, maximum observed bee abundances of a field were not associated with field size, weediness, or presence of commercial honeybee hives. However, long-tongued bumblebee abundance was significantly lower in fields with beehives. Seed yield was marginally higher in less weedy fields, but not significantly augmented by presence of bee hives.