COS 39-9
Museum collections are valuable depositories of ecological data: The case of the foraging behaviour of two extinct species of British bumblebee Bombus pomorum and Bombus cullumanus
In recent decades many species of bumblebee (Bombus spp.) have declined significantly in abundance and in the extent of their geographical range in the British Isles. Six species now have very restricted distributions and three species have become extinct. The principle cause of these declines is believed to be the loss and degradation of foraging habitat due to the post-war intensification of agriculture. Whilst the foraging strategies of extant species of bumblebees that inhabit these intensively managed landscapes has been well documented very little is known about the foraging strategy of either Bombus cullumanus (Cullum’s bumblebee) or Bombus pomorum (Apple bumblebee) that went extinct from the British Isles in the mid-twentieth and mid-nineteenth century respectively. The question this research aims to answer is what were the foraging strategies employed by these two extinct species of bumblebee. To achieve this aim under a stereo microscopy using a fine brush pollen was removed from the three only know British specimens of B.pomorum held at the Oxford University Museum of Natural History that were collected in 1857 and 1864 and from all of the specimens of B.cullumanus (n=15) that were collected c.1850, 1854 and 1923. The retrieved pollen grains were mounted in silicon oil and identified to the lowest taxonomic level (species, genus or family) using light microscopy.
Results/Conclusions
The pollen recovered from B.pomorum represents 12 different families of plant including Apiaceae, Asterceae, Brassicaceae, Lamiaceae and Onagraceae. This suggests that this rare species of bumblebee when present in the British Isles adopted a generalised foraging strategy, visiting any available floral resources in its coastal habitat that consisted of coastal vegetated shingle, sand hills and open grassland. That these specimens of B.pomorum are the last ever recorded suggests that a lack of floral resources was not the cause of this species extinction. In contrast, B.cullumanus that also inhabited coastal habitats and chalk grasslands foraged almost entirely on plants belonging to the Asteraceae family. It is hypothesised that the primary factor that lead to B.cullumanus becoming extinct in 1941 was the intensification of agriculture at the start of World War II when many of the floral species rich grassland habitats it had occupied were ploughed up to increase domestic food production.