Bees and pollination in grassland habitats in Helsinki (Finland) are diverse but dominated by polylectic species

Abstract

Bees constitute a key taxon of grassland ecosystems and are the main providers of the essential Ecosystem Service of pollination. We studied bee assemblages of 17 grassland sites in Helsinki, Finland. Bees were sampled using coloured pan traps. The total catch comprised 353 individuals of 35 species. The most abundant species were Lasioglossum leucopus, Lasioglossum lucidulum and Bombus lucorum complex. We used NMDS ordination to depict habitat associations, and GLMM to model the responses of species and trophic groups to habitat type and level of urbanization. Polylectic ground-nesting species were the most abundant trait group. There were only few records of oligolectic species, which showed a significant preference for areas with the lowest level of urbanization. We recommend the provision and maintenance of a diverse range of grassland habitats, with particular attention to the conservation of late successional meadow habitats.