Overall and repeated floral visitation by insects suggests flower flies (Syrphidae) as the major pollinator group of Alaska Wild Rhubarb (Koenigia alaskana var. glabrescens; Polygonaceae) in Northwest Territories, Canada

Résumé

Alaska Wild Rhubarb (Koenigia alaskana var. glabrescens; Polygonaceae) is a native Arctic, subarctic, and alpine plant of northwestern North America. Although the plant has some economic and ecological importance, its biology is poorly known. At 11 sites in the northeast corner of its range in Northwest Territories, we found that 87% of its floral visitors were flies, mostly Syrphidae, a diverse family known to be important pollinators. Insects visiting consecutive flowers on different plants and, thus, likely effecting pollination were also flies (78.6%) and also mostly Syrphidae (72.7%) followed by Hymenoptera (20%). Although syrphids were the dominant potential pollinators at most sites, there was some variation among sites. Our results provide quantitative support for pollinator diversity and the major role of Syrphidae in pollination of Alaska Wild Rhubarb. We suggest that pollination is not a limiting factor in this plant’s spread, nor its rare and local occurrence and restricted distribution, because the majority of its pollinators are widespread.