News Release

Study shows the impact of genetic diversity on effective alligatorweed control

Peer-Reviewed Publication

Cambridge University Press

Alternanthera philoxeroides, commonly referred to as alligator weed

image: Alternanthera philoxeroides, commonly referred to as alligator weed view more 

Credit: Photo courtesy of Shutterstock

WESTMINSTER, Colorado - December 15, 2020 - New research featured in the journal Invasive Plant Science and Management (IPSM) shows that genetics matter when it comes to the effective control of alligatorweed, an invasive plant found in or near aquatic settings across the southern U.S. and California.

A biological control program launched in the late 1960s reduced the prevalence of the invader, but the results varied geographically. A multidisciplinary research team recently explored whether the differences in efficacy might be related to genetic differences among alligatorweed populations.

After genotyping nearly 400 plants collected from 90 sites, researchers found that U.S. populations of alligatorweed are genetically diverse across geographies. This suggests the plant has been introduced to the U.S. multiple times from its native South American habitat.

The team found six genetic variations of alligatorweed, including both narrow-stem and broad-stem genotypes known to respond differently to both herbicides and biological controls. Though further testing is required, it is suspected the remaining four genotypes may also differ in their response to control measures and climate.

"The genetic markers identified in this study provide a quick way to determine the types of alligatorweed present in a given area and to test various control strategies," says Dean Williams, a professor at Texas Christian University. "In some areas, a single genotype predominates and may respond more uniformly to a single control strategy. In other areas, though, there may be multiple genotypes that require a more varied approach."


To learn more, read the article "High genetic diversity in the clonal aquatic weed Alternanthera philoxeroides in the United States," which is currently available online.

About Invasive Plant Science and Management

Invasive Plant Science and Management is a journal of the Weed Science Society of America, a nonprofit scientific society focused on weeds and their impact on the environment. The publication focuses on invasive plant species. To learn more, visit

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