Potential Impacts of Hybridization on Control of a Heavily Managed Invasive Plant

Untitled Document
Aquatic Invasive Species (AIS): Eurasian Watermilfoil (Myriophyllum spicatum)
Project Location: Michigan, Muskegon County; Montana, Gallatin County
Project Start Date: 08/2012
Expected Timeframe/Duration: ongoing
Sponsoring Organization: Grand Valley State University
Montana State University
Web Links: http://www.gvsu.edu/geneticidentification/
Primary Contact: Syndell Parks
Grand Valley State University Annis Water Resources Institute

Secondary Contact: Ryan Thum
Montana State University
Project Summary:

We study the biology and management of hybrid watermilfoil. The overall goal of this project is to increase our understanding of how hybrid watermilfoil grow and spread, and how best to manage them.

Eurasian watermilfoil (Myriophyllum spicatum) is an invasive aquatic plant that is extensively managed with herbicides to mitigate its large economic and ecological impacts. Eurasian watermilfoil hybridizes with the ecologically benign and native northern watermilfoil (Myriophyllum sibiricum). Experimental studies from Thum’s laboratory demonstrate that, compared to pure Eurasian watermilfoil, hybrids frequently exhibit faster growth and reduced sensitivity to the widely-used herbicide 2,4-D. In addition, laboratory data demonstrate that hybrid watermilfoils have the potential to evolve herbicide resistance because distinct hybrid genotypes vary in how sensitive they are to herbicides; some are more sensitive than others. Thus, more sensitive genotypes can theoretically be replaced by less sensitive genotypes over time, as populations are managed with herbicides.

While the laboratory research has demonstrated important concepts regarding the relative invasiveness of pure Eurasian versus hybrid watermilfoil, current research investigates what actually happens during operational herbicide management. Detailed genetic monitoring is being performed to test the predictions that 1) hybrid watermilfoil will increase their distribution and abundance relative to pure Eurasian watermilfoil following herbicide treatment, and 2) herbicide resistance evolves in local populations as more sensitive genotypes are replaced by less sensitive ones.

Ultimately, we would like to take the knowledge gained from laboratory and field studies and translate it into risk assessment services that help aquatic plant managers develop environmentally and economically sustainable management practices.