Bumblebees in the city: abundance, species richness and diversity in two urban habitats

Bumblebees are well known for their contribution to the ecosystem service of pollination. In urban areas, green space management beneficial to pollinators can be an important step in sustaining large urban bee populations. The abundance, number of species and diversity of bumblebees (Bombus spp), as well as the abundance of honeybees (Apis mellifera), were studied in 13 urban gardens (including allotments) and 13 ornamental flowerbeds (in parks and green spaces) in the city centre of Gothenburg, Sweden. In total, 12 species of bumblebees were observed. Species richness was significantly higher in gardens than in flowerbeds, but diversity (Berger–Parker and Simpson indices) was higher in flowerbeds than in urban gardens. The abundance in gardens was significantly higher and approximately twice that found in flowerbeds. The number of honeybee individuals was positively correlated with the abundance of bumblebees. Neither species richness nor abundance of bumblebees was affected by site size. However, a high flowering frequency positively affected the total number of bumblebee and honeybee individuals at the sites. We conclude that urban gardens contribute to sustaining a high abundance of bumblebees in the city centre, and indirectly facilitates small scale urban food production. A pollinator-friendly management of urban green space with plentiful flowering may promote a community of bumblebees with high abundance and diversity.