INVESTIGATING THE COMPETITION BETWEEN HONEYBEE (APIS MELLIFERA) AND THE OLIGOLECTIC WILD BEE ANDRENA MARGINATA Pollinator use of Succisa pratensis and associated flower visitors in nature reserves in western Sweden

Sammanfattning

Wild bee populations have declined globally in recent decades, largely due to habitat loss, landscape fragmentation, and reduced floral resource availability, all are factors caused by changes in land-use. To what extent these changes have an impact on the pollen and nectar resources for wild bees are of great importance since the competition for food has increased due to the increasing number of honeybee colonies (Apis mellifera), and since beekeeping also has other negative effects. The aim of this study was to investigate factors affecting the abundance of the oligolectic wild bee Andrena marginata in nature reserves in western Sweden. Specifically, the study aimed to observe how the abundance of Succisa pratensis, the primary pollen resource for A. marginata, and the abundance of A. mellifera were related to the abundance of A. marginata. Also, the abundance of other pollinators and the abundance of the cuckoo bee Nomada argentata were investigated. Transect walks and capture-recapture methods were used to observe and estimate pollinators and flowering plant communities associated with S. pratensis. The phenology of S. pratensis appeared to be affected by grazing, and was identified as an important pollen resource for many late summer pollinators. Andrena marginata showed peak activity during the morning, coinciding with the main pollen release period of S. pratensis, suggesting that temporal matching between bee activity and floral resource availability may reduce competition and improve foraging efficiency. No evidence of a negative relationship between A. mellifera and A. marginata abundance was found, suggesting that direct competition between the two species was weak or not detectable. N. argentata was not observed. Overall, this study increases understanding of interactions between oligolectic wild bees and generalist honeybees in semi-natural habitats and highlights the importance of the conservation of particularly important flowering plants for oligolectic pollinators during late summer.