Andrena florea Fabricius, 1793 (Hymenoptera, Apoidea, Apiformes): a rare bee species in Poland, related to the expansion of the alien plant Bryonia dioica Jacq. (Cucurbitaceae)

Although research into alien species usually focuses on their negative aspects associated with their penetration into native ecosystems, their influence is much more complicated. This study investigated the pollinators of Bryonia dioica, an invasive climber in the temperate zone. Flowers of this plant in two cities in western Poland (Bydgoszcz and Poznań) were visited by 27 bee species, the most frequent ones being Apis mellifera and Andrena florea. Until recently, the latter was regarded as rare and threatened in Poland. Our results indicate that the spread of Bryonia dioica into urban areas has enabled large and stable populations of Andrena florea to flourish there. This study investigated the daily and seasonal dynamics of its activity. A positive relationship was found between the spread of Bryonia dioica and the presence of its obligatory pollinator Andrena florea. Alien plant species are thus not only an additional source of food for local pollinators but also may favour the occurrence of otherwise rare species with specific food requirements, such as A. florea.