Plant Biol (Stuttg) 2005; 7(5): 541-548
DOI: 10.1055/s-2005-865855
Research Paper

Georg Thieme Verlag Stuttgart KG · New York

Broom and Honeybees in Australia: An Alien Liaison

S. R. Simpson1 , C. L. Gross1 , L. X. Silberbauer1 , 2
  • 1Ecosystem Management, University of New England, Armidale, NSW 2350, Australia
  • 2Current Address: Biological Sciences, Macquarie University, NSW 2109, Australia
Further Information

Publication History

Received: April 4, 2005

Accepted: June 21, 2005

Publication Date:
15 September 2005 (online)


Facilitative interactions between non-indigenous species are gaining recognition as a major driver of invasion success. Cytisus scoparius (L.) Link (Fabaceae), or Scotch broom, is a cosmopolitan invasive shrub that lacks the capacity for vegetative reproduction and is a good model to study facilitative interactions. Its success in pioneer environments is determined by constraints on its reproduction. We determined whether pollinators were required for seed set in C. scoparius at Barrington Tops, NSW, Australia, where the species has infested ca. 14 000 ha across the plateau. Field and laboratory experiments showed that C. scoparius is an obligate outcrossing species at Barrington Tops. Monitoring of plants (10.7 h) showed that the flowers of C. scoparius have to be tripped to effect seed set and the only pollinator to do this was the introduced honeybee, Apis mellifera L. Most floral visits by honeybees result in fruit set (84 %) and because fruits have many ovules (10 - 18 per ovary) a single bee on an average foraging day can effect the production of over 6000 seeds. A review of C. scoparius pollination across four continents revealed major differences in pollen quantity, which may explain differences in the efficiencies of honeybees as pollinators of C. scoparius. The incorporation of pollinator management in an integrated approach for the control of C. scoparius is discussed.


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S. R. Simpson

Department of Ecosystem Management
University of New England

Armidale, NSW 2350



Editor: S. S. Renner