Study: Invasive plant 'success' a myth

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AMES, Iowa, March 1 (UPI) -- Invasive plant species, although widespread, are no more abundant in their new homes than in their native area, a U.S. researcher says.

"There is this assumption that when plants invade a new area that they become much more abundant in the new area than they were in the native areas," Iowa State University ecology Professor Stan Harpole said in an ISU release issued Tuesday. "It turns out that, on average, they aren't any more abundant away from home than they are at home."

Previous assumption held that problematic invasive species often spread widely in their new habitats because they don't encounter predators or diseases that help keep them in check in their home ranges.

Harpole organized a team of more than 70 researchers surveying 65 sites around the world to test that assumption.

Harpole says there's a "rule of 10s" than can be found with invasive species.

"Of, say, 100 plants that arrive in a new area, only about 10 percent of those will survive without being in a greenhouse or some other controlled area," Harpole says. "Of those 10 that can survive, only about 10 percent of those really cause problems."

Problem plants are uncommon when compared to all species in a region, but get the most attention and may give the impression that species spread and take over new habitats and become more abundant than at home, Harpole says.

Even plants now considered native were once invaders themselves, says Harpole.

"What's different today is that we move plants so much faster than they would move by themselves. Now a species can become global in a matter of years, where it may have taken tens of thousands of years in the past," he says.