Bumblebees at an alpine site in northern Sweden: temporal development, population size, and plant utilization

• Published in: Ecography
• Main Authors: Stenström, Mikael, Bergman, Peter
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1998
• Subjects: Ecology, Evolution, Behavior and Systematics; Northern Sweden; Saxifraga oppositifolia
• Online Access: http://dx.doi.org/10.1111/j.1600-0587.1998.tb00568.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1600-0587.1998.tb00568.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-0587.1998.tb00568.x

The bumblebee community in an alpine valley in northern Sweden was studied for two seasons. Only two species of bumblebees, Bombus alpinus and B. hyperboreus. are common at the site. Bombus hyperhoreus is an obligate nest parasite on B. alpinus : the latter species is four times more abundant than the former. The number of captures on any given day was very low. However, the number of queens foraging in the area was estimated by a mark‐reacapture method to ca 350 specimens, indicating that the queens forage over large areas. The dates for capturing queens carrying pollen in their corbiculae and the emergence of workers and males indicate that the queens only have time to produce one batch (or possibly two overlapping batches) of workers. The utilization of different plant species corresponds well with their flowering phenology at the site. The unspecialized flowers of Saxifraga oppositifolia are the main pollen and nectar source in the early part of the season. The bumblebees switch to Astragalus alpinus and Bartsia alpina as soon as they come into flower: these species show a typical bee pollination syndrome, the corbicular loads most commonly consisted of 91‐100% of pollen from a single species. The change in flower utilization and the composition of the corbicular loads give no support for the hypothesis that aretie bumblebees should be more generalistic in their foraging than temperate species. The preference for Astragalus and Bartsia will probably have an effect on outcrossing in late‐flowering specimens of Saxifraga oppositifolia , which has a very extended flowering period.