No severe genetic bottleneck in a rapidly range-expanding bumblebee pollinator

Genetic bottlenecks can limit the success of populations colonizing new ranges. However, successful colonizations can occur despite bottlenecks, a phenomenon known as the genetic paradox of invasion. Eusocial Hymenoptera such as bumblebees (Bombusspp.) should be particularly vulnerable to genetic bottlenecks, since homozygosity at the sex-determining locus leads to costly diploid male production (DMP). The Tree Bumblebee (Bombus hypnorum) has rapidly colonized the UK since 2001 and has been highlighted as exemplifying the genetic paradox of invasion. Using microsatellite genotyping, combined with the first genetic estimates of DMP in UKB. hypnorum, we tested two alternative genetic hypotheses (‘bottleneck’ and ‘gene flow’ hypotheses) forB. hypnorum's colonization of the UK. We found that the UK population has not undergone a recent severe genetic bottleneck and exhibits levels of genetic diversity falling between those of widespread and range-restrictedBombusspecies. Diploid males occurred in 15.4% of reared colonies, leading to an estimate of 21.5 alleles at the sex-determining locus. Overall, the findings show that this population is not bottlenecked, instead suggesting that it is experiencing continued gene flow from the continental European source population with only moderate loss of genetic diversity, and does not exemplify the genetic paradox of invasion.

Flower Preferences of the Wrocław Botanical Garden Bumblebees (Bombus spp.)

Bumblebees (Bombus spp.) are morphologically different from each other as determined by the length of their tongue. Seven species of bumblebees were identified in the Wrocław Botanical Garden: the long-tongued Bombus hortorum, and the medium-tongued B. pascuorum, and the 5 short-tongued species, Bombus hypnorum, Bombus lapidarius, Bombus terrestris, Bombus lucorum, and Bombus pratorum. Bumblebees were observed so that their choice of food within the botanical family could be determined. The shape and colour choice of the flower was particularly noted. Bumblebees showed the highest degree of preference for the Lamiaceae family. The Boraginaceae family was also used by all of the recorded species. Bumblebees found pink and purple, lipped, capitular/ globular, and saucer-shaped flowers to be most attractive. The individual species of bumblebees showed different preferences, which may be explained by the differences in their morphology. However, bumblebee flower preference and selection seems to be more complex and requires further, detailed research.