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Posted May 2009

Climate change has stimulated demand for models of how changing weather patterns will affect the distribution of both native and exotic species.

But a 2007 research paper finds that predictions for invasive species based on the climatic conditions in their native ranges are apt to be wrong.

Studying the invasive spotted knapweed (Centaurea maculosa), Olivier Broennimann, from the University of Lausanne, and his colleagues found that the aggressive, introduced weed occupies a different climatic niche in western North America than it does in its native Europe.

They also discovered that none of the native populations grow in a similar climate to the vast majority of the invading populations.

The range differences could result from hybridisation or evolution of
greater competitiveness in the invasive forms, and/or freedom from the herbivores, diseases or parasites that constrain spread in their native range.

In its new range, spotted knapweed has been shown to benefit from the
lack of competitive neighbours, soil pathogens and root-eating insects
in its native range. It typically grows more densely in areas it has invaded.

The evidence that invasive species can spread into new climatic zones casts some doubt on the value of models for predicting invasion potential.

The models may consistently underestimate the area invasive species can occupy.

References
Broennimann O, Treir UA, Muller-Scharer H, Thuiller W, Peterson AT, Guisan A. 2007. Evidence of climatic niche shift during biological invasion. Ecology Letters 10: 701-709.

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