, Volume 49, Issue 3, pp 219–224 | Cite as

Invaders, weeds and the risk from genetically manipulated organisms

  • M. Williamson
Multi-author Reviews Gene Technology and Biodiversity


Invaders, weeds and colonizers comprise different but overlapping sets of species. The probability of successful invasion is low. The 10:10 rule state that 10% of introduced speices (those with feral individuals) become established, 10% of established species (those with self-sustaining populations) become pests. The rule gives an adequate fit to British plant data. The rule predicts that invaders will be rarer than natives. This is shown for British Anatidae. There is a continuous spectrum of perceived weediness. Although this spectrum is significantly related to Baker characters, neither those characters or any others can usefully predict which species will be weeds over a wide range of species. Characters tuned to sets of closely related species shown more promise. A study of BritishImpatiens shows that the characters responsible for critical ecological behaviour are still obscure. Small genetic changes can cause large ecological changes. GMOs will have characters entirely new to that species' evolutionary history. While most will have little ecological effect, a few may be ecologically and economically damaging. A sensible programme of field trials and monitoring is justified to minimize the risk.

Key words

Invaders weeds Baker characters Impatiens GMOs 


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Copyright information

© Birkhäuser Verlag Basel 1993

Authors and Affiliations

  • M. Williamson
    • 1
  1. 1.Department of BiologyUniversity of YorkYork(England)

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