Why do non-native species tend to outcompete local breeds?

> To compare genetic diversity between invasive and indigenous plants, University of Vermont evolutionary ecologists Sébastien Lavergne and Jane Molofsky measured allozyme variability and growth traits in reed canarygrass (Phalaris arundinacea L.) from its native Europe and introduced populations in North America. They found that both genetic diversity and heritable phenotypic variation were greater in the invasive range than in the indigenous range, even at the population margins.

> "Multiple introductions can produce evolutionary novelty that wasn't in existence in the native range," says Stephen Keller of the University of Virginia. Thus, repeated introductions of non-native species should help invasive species better respond to global climate change, notes Molofsky.

> Last year, researchers from the University of Montpellier in France showed that an invasive population of freshwater snails on the island of Martinique harbored a tremendous amount of genetic diversity stemming from repeated invasions followed by genetic mixing (Curr Biol, 18:363–7, 2008). Every introduction "resembles a keg of dynamite" that provides fuel for evolutionary change, says Steve Novak, a plant ecologist at Boise State University.

-- 
S. Lavergne and J. Molofsky, "Increased genetic variation and
evolutionary potential drive the success of an invasive grass," Proc
Natl Acad Sci, 104:3883–8, 2007.

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