Conservation and foraging ecology of bumble bees in urban environments
The decline of British bumble bees has been attributed to the loss of their habitat through the intensification of agricultural practices. In the quest for information of use to bumble bee conservation the potential of our flower-rich cities has been overlooked. The overall aim of this study was to determine the status and foraging requirements of bumble bees in the urban environment provided by the city of London, U.K. My principal findings are as follows. Six common species and three rare species were identified. The greatest diversity of Bombus species was found in the east of London. Garden and wasteland habitats attracted the greatest abundance of workers and diversity of Bombus species. The distribution of Bombus humilis (a Biodiversity Action Plan Species) was found to follow the strip of derelict Thames-side industrial land on the eastern side of London as far west as the Millennium Dome, and the River Lea as far north as the Walthamstow Marshes. The phenology of B. humilis in London was established. The majority of all observations of foraging B. humilis were on flowers in the Lamiaceae family but species native to the U.K. were not necessarily its favoured forage. In a field experiment, the removal of potential competitors significantly increased the time that B. humilis workers spent foraging at patches of flowers. Microsatellite analysis was successfully employed to test three hypotheses concerning the movement patterns of foraging Bombus workers at three spatial scales. Neither B. terrestris nor B. pascuorum workers were found to forage with their nest-mates on patches of flowers. Mean numbers of 96 and 66 colonies of B. terrestris and B. pascuorum respectively were identified foraging on sites with a mean area of 0.8 hectares. No inbreeding and little or no genetic differentiation could be detected in either species across London.