A team of California scientists made headlines four years ago when it reported finding one of the largest insect colonies in the world - a 600-mile-long subterranean network of Argentine ants stretching from Northern California to the Mexican border. According to the researchers, this "supercolony" is made up of billions of closely related workers - all direct descendants of a small group of Argentine ants that were accidentally introduced into California more than a century ago.But new studies by Stanford University scientists are raising serious doubts about the existence of a single supercolony running through the Golden State. The Stanford team questions the notion that Los Angeles ants are descended from the same founding population as San Francisco ants, which live 400 miles away. A more likely explanation, they say, is that California has been infested by numerous colonies of genetically distinct Argentine ants during the last 100 years. Challenging the supercolony paradigm is more than an academic exercise, says Stanford biologist Deborah M. Gordon. Argentine ants have had a major impact in many parts of the world, she says, and understanding how they reproduce and colonize is essential if scientists hope to develop realistic strategies that will keep their populations in check. "Our data show that it's not the case that the whole California coastline is one genetically homogenous supercolony," says Gordon, a professor of biological sciences. "We find a lot of genetic diversity here, which indicates that there were probably many introductions in the past."
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