The impacts of an invasive alien plant and its removal on native beesCaroline Marijke Nienhuis, Anke Christiane Dietzsch and Jane Catherine Stout
Botany Department, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
Received 25 April 2008 – Revised 20 November 2008 – Accepted 2 December 2008 - Published online 8 August 2009
Abstract - Although the alien Impatiens glandulifera successfully invades riparian habitats and is visited by native insects, knowledge of its impact on native bees is limited. We assessed pollinator abundance in field sites where I. glandulifera was absent, present or had been experimentally removed. We measured insect visitation to flowers of potted native plants and to I. glandulifera. Bombus spp. comprised the highest proportion of visitors in invaded sites, whereas solitary bees made up the highest proportion in sites where I. glandulifera was removed. More bees, especially medium- and long-tongued Bombus spp. (B. pascuorum and B. hortorum), foraged on I. glandulifera than the native plant species (possibly because the alien was more abundant). We detected no impact of invasion on standardised pollinator abundance, B. pascuorum abundance, nor functional insect diversity, which may be due to variable climatic conditions. We suggest that future studies focus on impacts on rare or specialised pollinator taxa.
Key words: Bombus / Impatiens glandulifera / nectar secretion rate / nectar sugar concentration / Syrphidae
© INRA, DIB-AGIB, EDP Sciences 2009