Potential impact of Nootka lupine invasion on pollinator communities in Iceland

Abstract

Declines in abundance and diversity of pollinating insects are widely documented throughout Europe. Invasive alien plant establishment is one of the numerous factors threatening pollinator communities. Throughout much of Iceland, the alien plant Nootka lupine (Lupinus nootkatensis) has established competitive colonies that have replaced native flowering plants. The reduction of flowering plant diversity associated with the spread of Nootka lupine could severely impact pollinators that are well-adapted to foraging on native flowering plants. The present study aimed to investigate how pollinator communities may be affected by the spread of Nootka lupine. It was expected that pollinator communities observed foraging on native flowering plants would be more diverse than those foraging on Nootka lupine. From June to August 2015, insects were collected from the flowers of Nootka lupine and native flowering plants in the heath adjacent to Lake Vifilsstaðavatn, in Heiðmörk, a conservation area in southwest Iceland. Specimens were later identified, and pollinator communities of Nootka lupine and native heath wildflowers were analyzed. Data gathered in this study suggests that Nootka lupine cannot sufficiently serve as a supplemental- and alternative food resource for Iceland’s insect pollinators. A number of Iceland’s pollinating taxa, including Iceland’s only native bee species, the heath bumblebee (Bombus jonellus), are at risk of severe population declines if Nootka lupine continues to replace native flowering plants throughout Iceland. Conservation of floral resources for insect pollinators should include both restoration and preservation of native wildflower communities, and eradication and control efforts to replace invasive plant communities with native species.