Adaptability to local climate helps invasive species thrive

According to new research published in Science by University of British Columbia evolutionary ecologist Rob Colautti, rapid evolution has helped purple loosestrife to invade, and thrive in, northern Ontario.

"Factors such as escape from natural enemies including herbivores, predators, pathogens or parasites were thought to explain how species become invasive," says Colautti, an NSERC Banting Postdoctoral Fellow with the UBC Department of Botany, who started the research in 2007 as a PhD student at the University of Toronto. "The ability of invasive species to rapidly adapt to local climate has not generally been considered to be an important factor affecting spread.

"We found that the evolution of local adaptation to climate in purple loosestrife increased reproduction as much as or more than escaping natural enemies. Understanding that species can evolve rapidly to local climates is important for predicting how invasive species spread and how native and non-native species alike will respond to climate change."

To determine whether populations have evolved local adaptation, Colautti and University of Toronto professor Spencer Barrett collected seeds from three different climatic regions and grew them at three sites spanning the distribution of the species in eastern North America. They found that 'home' plants collected from latitudes most similar to each common garden location always had higher fitness than the 'away' plants.

They then measured Darwinian natural selection on flowering time and found differences in flowering times that have evolved over the past 50 years as the species moved northwards, following its initial introduction to the east coast of the USA.