Monitoring of bumblebee assemblages in the alpine zone of Daisetsuzan National Park.
In 2011, the Monitoring Sites 1000 Project conducted by the Biodiversity Center of Japan started monitoring bumblebee assemblages in alpine ecosystems. This report summarizes the results from Daisetsuzan National Park. We observed the species composition of bumblebees and their flower use pattern at the Akadake site from early June to late August. We recorded 473 bumblebees during 12 observation periods consisting of Bombus hypocrita sapporoensis (60%), B. hypnorum koropokkrus (18%), B. beaticola moshkarareppus (14%), B. yezoensis (1%), and B. diversus tersatus (1%). The introduced species, B. terrestris, was not observed. The frequency of bumblebees showed a bimodal pattern in mid-June (by overwintered queens) and after late July (by workers). Bumblebees visited flowers of about 40 plant species. Comparisons of bumblebee assemblages among three locations during the later periods revealed apparent differences in species compositions. B. beaticola was the most common species at the Kurodake site, while B. hypocrita represented more than 90% of the individuals observed at the Hisago-Numa site. One worker of the introduced species B. terrestris was noted at the Hisago-Numa site although it seemed to be an accidental visit to the alpine area from a lowland colony. Continuous monitoring of bumblebee assemblages in alpine sites is necessary to detect global warming impacts on species composition and the expansion of introduced organisms into alpine ecosystems.