Bumblebees (Hymenoptrea, Apidae) as visitors of Impatiens glandulifera Royle (Balsaminaceae) in the city of Tomsk (Western Siberia, Russia)
Impatiens glandulifera Royle is now widely known as an aggressive alien species of Himalayan origin in the temperate regions of Europe, Asia, North America and New Zealand. Having high potential for habitat-forming, Impatiens glandulifera becomes an important element of urban flora. Thanks to abundant and prolonged flowering, high content of nectar and pollen in the flowers, Impatiens glandulifera is very attractive to honey bees and bumblebees. In the flora of Tomsk, Impatiens glandulifera began to spread actively from the 80-ies of the last century. The given research is based on the material collected during the growing season in 2012. We studied the species composition and ecological characteristics of some complex bumblebees - Impatiens glandulifera visitors in parks and in built over areas of Tomsk (Western Siberia, Russia). In general, we collected 924 specimens of bumblebees, of which 515 from Impatiens. Species abundance classes were distinguished by their proportions in collections (Sysoletina LG) and according to a logarithmic five point scale (Pesenko YA). Bumblebee species are classified by their proboscis length according to Adakhovsky DA. For more detailed characteristics of bumblebee trophic interactions, we investigated the composition of pollen loads of workers collected on Impatiens flowers.We registered 14 species of bumblebees, including three dominant, five common and six rare species in the area. Visits of bumblebees on Impatiens glandulifera lasted from the middle of July (the beginning of the mass plant flowering) until the second decade of September. Bombus pascuorum (54.6%) and B. hypnorum (10.1%) dominated. We showed that forest species of bumblebees Bombus consobrinus and B. schrencki live on the territory of Tomsk and visit Impatiens glandulifera for pollen and nectar. In the second half of summer and early autumn, impatiens was an important source of nectar for workers and reproductive individuals of long-tongued species of bumblebees. On the flowers of Impatiens glandulifera the proportion of individuals of six species of long-tongued bumblebees was 77.3%. In the pollen loads of working individuals of different bumblebee species collected on Impatiens glandulifera flowers, pollen grains of the same plant prevailed (79-100%). In the future it is necessary to study the effectiveness of Impatiens glandulifera pollination by insects, especially dominant species Bombus pascuorum, and to assess a possible introduction of this plant in natural biotic communities, as well as a further research of its role in the preservation of the urban populations of bumblebees.