alien invaders leave their enemies behind

Plants such as kudzu and animals such as zebra mussels, which can be harmless in their country of origin, can be a pest elsewhere, playing havoc with local wildlife and having huge economic costs. Two studies in the Feb. 6 Nature report that one reason invasive species are so successful is because the enemies that kept them in check at home are usually left behind. Ecologists from Cornell University examined invasive plants, and researchers from the University of California at Santa Barbara studied invasive animals. It was found that, in general, invasive species had only half as many parasites and pathogens as native species. How do they manage to ditch their enemies? One hypothesis is that for parasites that live on more than one host species, a migration of two or more species might be required for them to survive. According to both studies, one way to control invaders would be to import their original enemies, but if the introduced pest turns out to like native species, too, that opens a whole new can of parasites.

This news brief appeared in the Random Data column of the Boston Globe’s Health/Science section on 2/18/2003.
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