Native plants on a California reserve (in bloom on mounds in background) are found in marginal, patchy habitats following invasion by exotic grasses (in green in foreground). Ecologists at the University of Toronto and ETH Zurich have found that, given time, invading exotic plants will likely eliminate native plants growing in the wild despite recent reports to the contrary. James Cornwell

Contact: Benjamin Gilbert, Department of Ecology and Evolutionary Biology, University of Toronto, 416-978-4065  (office), 647-778-0900  (cell) benjamin.gilbert@utoronto.ca

TORONTO, ONTARIO (University of Toronto) – Ecologists at the University of Toronto and the Swiss Federal Institute of Technology Zurich (ETH Zurich) have found that, given time, invading exotic plants will likely eliminate native plants growing in the wild despite recent reports to the contrary.

A study published in Proceedings of the National Academy of Sciences (PNAS) reports that recent statements that invasive plants are not problematic are often based on incomplete information, with insufficient time having passed to observe the full effect of invasions on native biodiversity.

"The impacts of exotic plant invasions often take much longer to become evident than previously thought," says Benjamin Gilbert of U of T's Department of Ecology & Evolutionary Biology (EEB) and lead author of the study. "This delay can create an 'extinction debt' in native plant species, meaning that these species are slowly going extinct but the actual extinction event occurs hundreds of years after the initial invasion."

Much of the debate surrounding the threat posed to biodiversity by the invasions of non-native species is fueled by recent findings that competition from introduced plants has driven remarkably few plant species to extinction. Instead, native plant species in invaded ecosystems are often relegated to patchy, marginal habitats unsuitable to their nonnative competitors.

However, Gilbert and co-author Jonathan Levine of ETH Zurich say that it is uncertain whether the colonization and extinction dynamics of the plants in marginal habitats will allow long-term native persistence.

"Of particular concern is the possibility that short term persistence of native flora in invaded habitats masks eventual extinction," says Levine.

Invading species can extinguish native plants despite recent reports

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