Biologist studies climate threat to some native prairie plants

Matthew A. Etterson

U.Va. biologist Julie Etterson inspects one of the pea plants, Chamaecrista fasciculata, that she’s growing in the department’s greenhouse.

By Fariss Samarrai

A common Great Plains prairie plant, the partridge pea (Chamaecrista fasciculata), could face severe reduction in numbers if climate conditions in the Midwest change to the extremes predicted for the next 25 to 35 years, according to a study to be published in the Oct. 5 issue of the journal Science.

If the partridge pea is threatened by changing conditions, other common native species may be threatened as well.

"The partridge pea's ability to adapt to rapidly changing climate conditions is likely to be much slower than the rate of climate change predicted for its native habitat throughout the Midwest," said the study's principal investigator, Julie R. Etterson, a post-doctoral research associate in biology at the University of Virginia.

Etterson was a Ph.D. student at the University of Minnesota when she conducted the study.

According to the climate model used by Etterson for her study, Minnesota's climate in 25 to 35 years is predicted to be similar to today's climate in Kansas, which is drier and warmer than Minnesota's. Under extreme conditions in a worst-case scenario, Minnesota's climate could become more like current-day Oklahoma -- much drier and warmer. Etterson's study indicates that native prairie plants could be seriously threatened if these predictions hold true.

"The partridge pea's evolutionary response for adaptation to hotter and drier conditions is unlikely to be fast enough to ensure its survival," Etterson said.
Etterson planted seeds from Minnesota partridge peas in Kansas and Oklahoma. She also planted Kansas partridge peas in Oklahoma. She found that seed production of Minnesota plants dropped 84 percent when grown in Kansas, and 94 percent when grown in the hotter and drier conditions of Oklahoma. The Kansas partridge pea plants dropped 42 percent when grown in Oklahoma. She also studied leaf number and leaf thickness, traits that are important indicators of drought tolerance, and found that the transplants were less adapted than local plants of the same species grown in the same plots.

"Native plants in the Midwest are facing two problems that may negatively affect their future survival," Etterson said. "One, the predicted rate of climate change is much more rapid than has occurred previously; and two, the habitat of native plants is fragmented to isolated islands between farms and cities, making it difficult for plants to slowly migrate to areas with more favorable conditions. This means plants will have to rely more on their evolutionary response to changing conditions. The partridge pea is unlikely to adapt to changing conditions quickly enough."

Etterson emphasizes that her findings are specific to the species she studied, the partridge pea. "The species could possibly develop some incremental adaptive responses to climate change during the next 25 to 35 years, but the responses are unlikely to be rapid enough. Our findings suggest that we should not assume that plant populations will evolve fast enough to keep pace with climate change. We may need to think about alternative management strategies for native species if the climate predictions prove to be accurate."