(Santa Barbara, Calif.) Globalization of commerce, especially by ships and air traffic, transports hitchhiking plants and animals around the world and in many cases they become pests in the new location according to an article in the February 6 issue of the journal Nature. One advantage that could explain their success is that the invaders often arrive without the parasites that hold them in check at home.

First author Mark E. Torchin, assistant research biologist at the University of California, Santa Barbara, said that the team of authors analyzed 26 invading animal species mollusks, crustaceans, fishes, birds, mammals, amphibians and reptiles chosen randomly, and found that, in general, the introduced populations had only half as many parasites as native populations.

"On average, an animal has 16 parasites at home, but brings less than three of these to new areas that it invades," said Torchin. "In the new region, parasites are not well matched to novel hosts, and only about four parasites will successfully attack an invading species."

On this research Torchin teamed up with co-authors Kevin Lafferty, an assistant adjunct professor of biology at UCSB and a marine ecologist with U.S. Geological Survey; Armand Kuris, professor of biology at UCSB; his graduate student, Valerie McKenzie; and Andrew Dobson, professor in the department of ecology and evolutionary biology at Princeton University.

Kuris explained that parasites are so pervasive that parasitism is the most common lifestyle on Earth. Many parasites don't just make animals sick they may castrate them, change their behavior, or even kill them. By leaving parasites behind, introduced species have a strong advantage over less fit native competitors which remain fettered by their own full complement of parasites.

Borrowing from popular culture, Lafferty said, "Parasites are to invasive species what kryptonite is to Superman. On his home planet Krypton, kryptonite was a regulator, k
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Contact: Gail Gallessich
gail.g@ia.ucsb.edu
805-893-7220
University of California - Santa Barbara
5-Feb-2003

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