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Oecologia

, Volume 146, Issue 3, pp 394–403 | Cite as

Higher pollinator effectiveness by specialist than generalist flower-visitors of unspecialized Knautia arvensis (Dipsacaceae)

  • Magnus LarssonEmail author
Plant Animal Interactions

Abstract

A critical issue in pollination ecology is the evolution of generalist pollination systems, and under which conditions floral specializations evolve from these. The gynodioecious herb Knautia arvensis (Dipsacaceae) exhibits a generalized pollination system, but is visited by both generalist and specialist flower-visitors. The present study tested pollinator effectiveness and pollinator importance of the pollen specialist solitary bee Andrena hattorfiana (Andrenidae) vs. the generalist flower-visitors to K. arvensis on the island of Öland, SE Sweden. Females of the specialist bee removed more pollen per inflorescence-visit than the major groups of generalist visitors such as bumblebees and flies. They also deposited more pollen per inflorescence-visit than any of the generalist visitor groups. The females have a preference for pollen-presenting vs. stigma-presenting inflorescences, a pattern shared with most of the generalist flower-visitors. Females of the specialist exert such a strong preference that they, despite their great pollinator effectiveness, make modest contribution to pollen transfer in K. arvensis. The females of A. hattorfiana accounted for 14.2% of the overall visits and 5.8% of the total pollination, the rest being performed by generalist visitors and males of A. hattorfiana. This study shows that pollinator effectiveness of a specialist can be superior while generalist flower-visitors select floral characters towards generalization through their greater contribution to overall pollen flow.

Keywords

Apoidea Floral specialization Oligolecty Pollination 

Notes

Acknowledgements

I am grateful to my advisor L. A. Nilsson for support during various phases of the work. Also, J. Ågren gave helpful comments on the manuscript, and S. Karlsson assisted me on the graphical design. The text was improved by the comments of S. D. Johnson, J. D. Thomson and one anonymous reviewer. This project was produced within the Nature Conservation Chain (Swedish Biodiversity Centre), with financial support from The Swedish Environmental Protection Agency. For additional support I thank the Ingegerd and Viking Olof Björck, and Bjurzon foundations. I am indebted to the facilities provided by the Ecological Research Station of Uppsala University, Ölands Skogsby.

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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Department of Plant Ecology, Evolutionary Biology CentreUppsala UniversityUppsalaSweden

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