Eurasian and hybrid watermilfoil genotype distribution in Minnesota

Invasive Eurasian watermilfoil is known to hybridize with native Northern watermilfoil in some lakes in Minnesota. This hybrid watermilfoil is also invasive and some strains have shown resistance to management efforts including herbicide treatments. However, much is unknown about the genetic makeup, diversity, and distribution of hybrid watermilfoil throughout the state, making management efforts very difficult. 

In partnership with Montana State University, this project will quantify the genetic diversity of Eurasian, hybrid, and northern watermilfoil in sixty Minnesota lakes and will help answer questions such as:

  • Do different genotypes present increased invasiveness or tolerance to control techniques?
  • Are there patterns of hybrid watermilfoil invasion? Are plants hybridizing within a lake, or is one hybrid strain being moved among lakes?
  • How is hybrid watermilfoil interacting with native plant communities?

The collected watermilfoil samples will first be genetically identified as Eurasian, northern, or hybrid. Later, the hybrid samples will be genotyped using molecular genetic techniques to determine whether specific genotypes are widespread or have restricted distribution, related to management activities or environmental factors, or if they’re hybridizing within lakes.

Understanding the patterns of invasion as well as genetic diversity of this plant to help lake managers develop and refine management strategies.


As of January 2019, genetic identification is complete for 20 plants from 31 lakes that were sampled in 2018. Eurasian watermilfoil was found in 43 lakes, hybrid watermilfoil in 27, northern watermilfoil in 23 lakes, and all three taxa were found in four lakes. Among these taxa, Eurasian watermilfoil was found to be least genetically diverse. There was no within-lake diversity for Eurasian watermilfoil. Meanwhile, ten lakes had multiple hybrid watermilfoil genotypes; and northern watermilfoil was the most diverse, with most lakes having multiple different genotypes within lakes and no genotypes shared between lakes. Overall we have identified 8 Eurasian genotypes, 76 northern genotypes, and 57 hybrid genotypes in Minnesota.

In 2018, researchers selected and sampled 5 treatment and 5 control lakes with point-intercept surveys, in order to characterize the genetic composition and plant community structure. Treatment lakes were subjected to a range of herbicide treatments, and will be resampled to assess changes. Milfoil samples were collected from 33 lakes in 2017, and samples were sent to the Thum lab at Montana State University for genetic analysis. Eurasian watermilfoil was found in 19 lakes, hybrid watermilfoil was found in 18, northern watermilfoil in 10, and all three were found in one lake.

Instances of Eurasian, hybrid, and northern watermilfoil in Minnesota

Project manager: Ray Newman

Funded by: Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources

Project start date: 2017

Estimated project end date: 2019

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