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The Yale Alumni Magazine is owned and operated by Yale Alumni Publications, Inc., a nonprofit corporation independent of Yale University. The content of the magazine and its website is the responsibility of the editors and does not necessarily reflect the views of Yale or its officers. |
If you look out over many of America’s salt and freshwater marshes, you’re almost certain to spot a 6- to 12-foot high, plume-topped grass known as the “common reed.” Phragmites australis, as it’s called by botanists, certainly lives up to its common name; often, it grows in stands so dense that nothing else can survive. Scientists have long considered Phragmites to be an example of an invasive species at its worst—a foreign plant or animal that, when introduced into a new environment, runs roughshod over native organisms. Examples abound, from kudzu to zebra mussels, but biological detective Kristen Saltonstall '96MFS has recently shown that Phragmites is a more subtle enemy than anyone had ever supposed. “This is the story of a cryptic invader,” says Saltonstall, a graduate student in ecology and evolutionary biology who uses molecular methods to understand how one species came to dominate so many wetlands. The work may also help conservationists prevent Phragmites, or other alien organisms, from taking over new areas. Working with EEB professor Jeffrey Powell, Saltonstall learned that Phragmites was anything but a newcomer to the North American continent. “It’s been a component of marshes for thousands of years,” she explains, “and during that time, it grew with other species.” However, beginning about 150 years ago, something in the nature of Phragmites changed. The plant dramatically extended its range, and in places, it became aggressive, overrunning its neighbors. When Saltonstall examined DNA samples from various parts of the world (Phragmites grows on every continent except Antarctica), she discovered a surprising pattern. The native and neighborly U.S. plants carried a “made in America” genetic trademark, while the aggressors bore the fingerprints of Phragmites from Europe and Asia. Scientists suspect that this cryptic invasion began in American seaports in the northeast, when European reeds, which were used as packing material, were thrown away. Using molecular techniques and samples from herbariums and nature, Saltonstall chronicled the takeover in southern New England, from a turn-of-the-century landscape filled with the U.S. variety to the present. “There are simply no native types left in our area,” she says. Nobody knows why a plant that is well-behaved in Europe became such a problem in the U.S. “Phragmites is hard to kill,” says Saltonstall, “so this variety is here to stay.” But because conservationists can now tell friend from foe among the reeds—Saltonstall hopes to soon have an easier way of determining who’s who—wetland managers may be able to root out troublemakers before they have had time to overrun a region. In addition, the work should make it possible to select the right Phragmites to use in marsh reclamation projects. While the molecular approach offers a new tool to help protect the country’s biological integrity, there’s a chilling message to Saltonstall’s work. “There are invaders we don’t even know are there,” she explains. |
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