ITHACA, N.Y. -- Among 473 of the alien plant species that have invaded from Europe and become naturalized in the United States as noxious weeds, the "most successful" traveled light -- carrying fewer plant diseases from their native habitats -- and were more immune to New World plant diseases.

That is the conclusion of Cornell University ecologists after examining plant-health records on both sides of the Atlantic. The study, reported in the latest issue of the journal Nature (Feb. 6, 2003) by Charles E. Mitchell and Alison G. Power as "Release of invasive plants from fungal and viral pathogens," is particularly significant in that it reconciles two theories, dating back to Charles Darwin in 1859, about successful naturalization of invading species.

Their findings, the ecologists say, should encourage biological-control strategists to look for weed-control pathogens both in the invading weeds' native and adopted habitats. However, they warn that biological control can negatively impact native species and is no panacea. What most surprised Mitchell and Power was the finding that pathogens can help keep invasive plants in check.

"We're coming to realize we should be grateful for our native plant pathogens," adds Mitchell, a postdoctoral researcher in Cornell's Department of Ecology and Evolutionary Biology. "Invasive plants cost an estimated $33 billion a year to the U.S. economy, but the damage would be worse were it not for our native fungi and viruses that control invasive plants to some degree."

A parallel study of invasive animals, ranging from mollusks to mammals, reported in the same issue of Nature as "Introduced species and their missing parasites" by ecologists at the University of California-Santa Barbara and Princeton University, reached similar conclusions about aliens' success in new lands.

Both the plant study and the animal study sought data for two long-standing and much-debated theories, explains Power, a pro
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Contact: Roger Segelken
hrs2@cornell.edu
607-255-9736
Cornell University News Service
5-Feb-2003

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