Document: ANN-3-44-7

Effect of two introduced species on the pollinator activity on Epilobium angustifolium.

GEARHART, A.M.*

University of California, Berkeley, CA 94720 USA ¹

Abstract:
Introduced species are recognized as an important component of ecosystem change. While competition for soil and space resources between introduced and native plant species has been well documented, the impacts on native pollination ecology have received attention only recently. I am exploring in how two introduced species (Matricaria perforata and Linaria vulgaris) that share bumblebee (Bombus sp.) pollinators with a native species (Epilobium angustifolium) may affect the pollination ecology of this native plant. Plant species sharing pollinators may interact in either a competitive or facilitative (benefical) manner. To examine potential effects of the introduced species, I "invaded" patches of Epilobium with four cut or potted individuals of either Matricaria or Linaria during two flowering seasons (summers 1998, 1999). This method was intended to mimic the early stages of a biological invasion, in which the introduced plant would be relatively rare. Pollinator type and behavior was observed. Because other species were infrequent visitors, only Bombus data were analyzed. Pollinator approach rate and pollinator bout length did not differ among addition and control treatments at this density. Lack of a significant effect may demonstrate that a threshold exists below which introduced plants do not influence the pollination ecology of a native. Additionally, the fluid nature of the pollination web, with fluctuations in pollinator composition and abundance among years, may make real patterns difficult to detect.

Keywords: pollination, invasion, Bombus, Epilobium, Linaria, Matricaria

This abstract is being presented at: 10:30 AM in session:
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