Proc. R. Soc. B doi:10.1098/rspb.2009.2231 (2010)

The geographical spread of invasive, non-native species may be limited by how they adapt over climate gradients. To investigate, Robert Colautti of the University of Toronto in Canada and his co-workers combined mathematical modelling with field surveys and greenhouse experiments on purple loosestrife (Lythrum salicaria). This invasive wetland plant — native to Europe — is common in eastern North America, where its range is rapidly expanding. This allowed the researchers to see how changing conditions affect the plant's evolution.

The authors' model and experiments showed that plants that had adapted to more northern climes, where the growing season is shorter, had done so at a cost: they flowered earlier, but were smaller and produced fewer seeds. The authors suggest this constrained adaptation may ultimately limit the northern spread of this invasive plant.