Rogstad chose cattails for the study because they are widely distributed and morphologically complex.

In areas heavily impacted by pollution, researchers from the University of Cincinnati have detected significant genetic diversity among common cattails.

Their findings provide evidence that cattails might be an indicator of environmental stress within a given ecosystem.

The study, led by plant biologist Steven Rogstad, chose to examine cattails for several reasons. Cattails have a wide range of ecological tolerance, distributed widely from the Arctic Circle to the tropics. In addition, cattails exhibit great morphological complexity that is close to the complexity found in humans.

Rogstad said plants could be strong environmental indicators because unlike animals, which move from one location to another, "plants stay on site exposed to a full array of environmental stresses available at a site." Plants can also be useful in recording the history of mutation stress at a given site.

The researchers first sampled dozens of cattail populations along a 320-kilometer stretch from Louisville, Kentucky, to Circleville, Ohio (south of Columbus). Next, they sampled cattail population sites known to be contaminated with fuels, solvents and other organic chemicals on the Wurtsmith Air Force Base in northeastern Michigan.

Cattails growing in polluted sites were the most genetically diverse.

Leaf samples from the various sites were returned to UC labs where complex DNA sequencing patterns were extracted for comparison. By sampling a wide area in the Midwest and a site known to be polluted, the researches hoped to get a better picture of the genetic diversity in cattails and to determine if changes in genetic diversity could be an indicator of environmental stress.

The researchers were surprised to find that the cattails growing in the most polluted sites had the greatest genetic diversity. Second, Rogstad notes that "several previous studies with animals found that genetic diversity is often reduced with increasing levels of chemical pollution."

Possible explanations for this increased diversity include increased mutation rates or higher mortality driving the establishment of a more diverse set of individuals at a site.

"We are just at the beginning of trying to understand the effects of pollution on plant population genetics," said Rogstad. The University of Cincinnati lab is continuing to work in this area by examining diversity in a number of common plants from dandelions to honeysuckles and wild raspberries.

Rogstad said environmental stress indicators might be useful in finding out if an area with a history of pollution is suitable for human habitat.

The study, funded in part by the EPA, was published in the American Journal of Botany.

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