June 03, 2015

Jeanette Grider

Biology Graduate Student Publishes Research on Invasive Kudzu Plant

Research by Steven Callen, a Ph.D. candidate in the Department of Biology at Saint Louis University, on the devastating impact of the invasive kudzu plant in many parts of the United States, is gaining local and national attention.

Callen, a fifth year Ph.D. candidate in Dr. Allison Miller's lab at SLU, first became captivated by kudzu during his service as a high school biology teacher through the Teach for America program in Helena, Arkansas.

"The town was overtaken by this rapidly growing vine long ago," Callen said. "There, as well as in a majority of other Southern towns, kudzu forms these intensely thick mats of intertwined vines that grow over anything that remains in place for more than a few days and that are notoriously difficult to remove."

After coming back to St. Louis five years ago, Callen was surprised to learn that large patches of kudzu could be found within driving distance of SLU and, upon Miller's suggestion, decided it might be worth studying for his dissertation research.

Allison Miller, Ph.D., associate professor of biology at SLU and also a research associate with the Missouri Botanical Garden, is interested in evolutionary processes in long-lived, clonally reproducing plants like kudzu.

"Despite global concern about the continuing spread of kudzu in the United States and elsewhere, very little is known about the environments in which this species lives, or its capacity for reproduction and spread into new areas," Miller said. "Steven's work applies a comparative approach to understand how the environments where kudzu is found in North America resemble those of its native distribution in Asia. This is an important study for kudzu because it demonstrates that kudzu can live in conditions that are not found, or not currently occupied, in its native region of Asia. "

While native to East Asia, kudzu, known as the "vine that ate the South," is one of the economically and ecologically worst invasive plant species in the United States. Planted for more than 50 years in the early-to-mid 1900s as a means for controlling soil erosion and as food for livestock, kudzu now covers over seven million acres of land in the U.S. and costs approximately $336 million a year from management efforts and from damage to national infrastructures such as railway lines and telephone poles.

Despite its prevalence across the country, little is known about the types of environments under which it grows and how well those environments in the U.S. match areas where it grows in Asia. To gain insight into the importance of climate for kudzu, Callen and Miller characterized and compared the climates kudzu grows under in its native range in East Asia to those in its invasive range in the United States.

"We found that most climatic conditions for kudzu in the U.S. mirror those from populations in Asia, but that there are also invasive kudzu populations characterized by climates not experienced by native populations," Callen said. "We also found that there are large areas in the western United States that have climates that mirror those from kudzu's native range, but where kudzu is currently not found."

Callen said their results suggest that the opportunity currently exists for kudzu to expand its range even farther by spreading west into areas having climates similar to its native range and that kudzu also has the ability to establish populations in areas with climates that are unique relative to its native range, such as in the northern U.S.

"Populations on the edge of its current range, such as here in Missouri, may serve as sources for kudzu's potential western and northern expansion," Callen said. "As the large-scale dispersal of kudzu by people is largely responsible for its current U.S. distribution, efforts to minimize human-mediated dispersal, particularly in Missouri, are critical to prevent its future spread."

The best way to prevent its spread is simple: don't plant it.

"While individual kudzu patches certainly get larger over time, it is not clear how easily kudzu can spread into new areas on its own," Callen said. "Most populations seem to be established from plantings by people or from the unintentional movement of parts of the vine by farm equipment or other vehicles."

Successful removal of kudzu patches often requires several (up to 10) successive years of herbicide application and manual removal of the roots, which could otherwise sprout new vines. Some Southern counties have elected to fight kudzu invasion with goats, which eat kudzu down to its roots. Kudzu leaves resemble those of poison ivy and soybean, in that they consist of three leaflets, but are more deeply lobed, often have small, wiry brown hairs, and can be the size of a large man's hands. Kudzu can be readily identified by its purple flowers, which have a sweet scent, like that of grape Kool-Aid, and by its fruit, which resembles a long, hairy pea pod. If you find a patch of kudzu, please contact Steven Callen.

Work described here was supported by the Kunming Institute of Botany, the National Science Foundation East Asian and Pacific Islands Summer Institute, Saint Louis University Graduate Research Fellowship, the Webster Groves Nature Society, and through the Missouri Botanical Garden graduate program, Callen's research has been published in Diversity and Distributions.

For additional information, contact Steven Callen at scallen@slu.edu or (314) 591-0673.

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