Scholarship & Research
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/1
Browse
3 results
Search Results
Item Hybridization and invasiveness in Eurasian watermilfoil (Myriophyllum spicatum): is prioritizing hybrids in management justified?(Montana State University - Bozeman, College of Agriculture, 2021) Hoff, Hannah Katherine; Chairperson, Graduate Committee: Ryan Thum; Ryan A. Thum was a co-author of the article, 'Hybridization and invasiveness in Eurasian watermilfoil (Myriophyllum spicatum): is prioritizing hybrids in management justified?' submitted to the journal 'Invasive plant science and management' which is contained within this thesis.Hybridization can play an important role in the evolution of invasiveness. Eurasian watermilfoil (Myriophyllum spicatum L.) is a widespread aquatic invasive plant species that hybridizes with native northern watermilfoil (Myriophyllum sibiricum Kom.). Previous studies have found mixed evidence for whether hybrid watermilfoil (Myriophyllum spicatum x sibiricum) and pure M. spicatum differ in vegetative growth rate and herbicide response. While several studies have emphasized variation in these traits among M. spicatum x sibiricum genotypes, variation within M. spicatum has not been considered. Therefore, it is unclear how important genetic variation within M. spicatum, versus between M. spicatum and M. spicatum x sibiricum, is in influencing invasive traits and management outcomes. If M. spicatum x sibiricum genotypes are always more invasive than M. spicatum genotypes, simply distinguishing taxa may be sufficient for identifying lake management priorities; however, if significant phenotypic overlap is observed between taxa, distinguishing individual genotypes may be important for tailoring management strategies. We performed replicated trials of a vegetative growth and 2,4-D assay to measure clonal variation in growth rate and herbicide response of M. spicatum and M. spicatum x sibiricum. Our results indicate that M. spicatum x sibiricum exhibits higher average vegetative growth than M. spicatum, whether or not it is treated with 2,4-D. We did not observe interactions between taxon and treatment or between genotype and treatment. Despite differences between M. spicatum and M. spicatum x sibiricum in average vegetative growth, there was substantial overlap between taxa. For example, we found that the fastest-growing genotype of pure M. spicatum did not differ significantly in average growth from the fastest-growing M. spicatum x sibiricum genotype. The potential for overlap between these invasive Myriophyllum taxa suggests that distinguishing and characterizing genotypes may be more informative for management than simply distinguishing between M. spicatum and M. spicatum x sibiricum.Item Integrating DNA fingerprinting of invasive watermilfoil strains into aquatic vegetation monitoring and assessment(Montana State University - Bozeman, College of Agriculture, 2021) Gannon, Kathryn Alta; Chairperson, Graduate Committee: Ryan Thum; Raymond Newman and Ryan Thum were co-authors of the article, 'Integrating DNA fingerprinting of invasive watermilfoil strains into aquatic vegetation monitoring and assessment' submitted to the journal 'Journal of aquatic plant management' which is contained within this thesis.Eurasian watermilfoil (Myriophyllum spicatum L.) and its hybrids with native northern watermilfoil (Myriophyllum spicatum L. x Myriophyllum sibiricum) (invasive watermilfoils) are among the most heavily managed invasive aquatic plants in the United States. Within invasive watermilfoils there are distinct strains which are produced through sexual reproduction and can be maintained indefinitely by clonal propagation. Different strains can differ in their invasiveness (e.g., growth and potential for spread) and response to herbicides. However, strain identification is not routinely implemented as part of management planning or evaluation. In this thesis, we integrated molecular fingerprinting that can distinguish different Eurasian and hybrid watermilfoil strains into aquatic vegetation monitoring in eight Minnesota lakes over the course of three years. We provide proof of concept that by tracking strain incidence over time it is possible 1) to detect changes in strain composition of invasive watermilfoil populations, and 2) to identify priority strains for future growth and herbicide assays. This study demonstrates that integrating genetic fingerprinting into aquatic vegetation management and evaluation holds promise to inform management decisions by identifying those strains that have the most invasive potential. As far as we are aware, this is the first published study to examine the strain composition of invasive watermilfoil populations over time.Item Genetic surveys in combination with laboratory studies on growth and response to herbicide can help design, evaluate, and optimize Eurasian watermilfoil management plans(Montana State University - Bozeman, College of Agriculture, 2018) Guastello, Paula Ropp; Chairperson, Graduate Committee: Ryan Thum; Ryan A. Thum was a co-author of the article, 'Mesocosm evaluation of Eurasian and hybrid watermilfoil response to endothall in Jefferson Slough, Montana' in the journal 'Journal of aquatic plant management' which is contained within this thesis.Eurasian watermilfoil (Myriophyllum spicatum) is a top priority for aquatic plant managers in the United States. Dense mats of Eurasian watermilfoil obstruct irrigation and recreational activities, while drastically reducing property values and potentially providing a habitat for disease-carrying mosquitos. Nuisance populations are generally managed through herbicide use. Eurasian watermilfoil is capable of both sexual and clonal reproduction, creating a unique opportunity for adaptation: sexual reproduction generates genetic variation within a population, then fit genotypes can propagate via clonal reproduction. Pure Eurasian watermilfoil is genetically diverse, and additional genotypes result from frequent hybridization with native northern watermilfoil (Myriophyllum sibiricum). Recent studies have shown that genetic variation in Eurasian watermilfoil populations may affect herbicide efficacy in managed populations. Given the variability in herbicide response, I propose conducting site-specific studies to evaluate the response of genotypes in a waterbody to evaluate and optimize management strategies. In my thesis, I evaluated the potential to control nuisance pure and hybrid Eurasian watermilfoil with endothall in a riverine environment (Jefferson Slough, Montana). Molecular genetic surveys indicated that only one genotype of each taxon was present throughout the slough. I first compared vegetative growth and endothall response of the hybrid and Eurasian genotypes in the greenhouse, where I did not identify a difference in endothall sensitivity. Next, I evaluated the efficacy of an operational endothall treatment in Jefferson Slough. Similar to the greenhouse study results, hybrid and Eurasian watermilfoil were reduced to the same average biomass seven weeks after operational endothall treatment. Taken together, the greenhouse and operational field treatment indicate that the genotypes in Jefferson Slough were similarly susceptible to endothall. However, vegetative growth differences may have important management implications over time. In the greenhouse, Jefferson Slough hybrids grew significantly more than Eurasian watermilfoil in the absence of endothall. Additionally, there was a qualitative shift towards higher frequency of hybrids where the taxa intermixed. These results suggest a relatively higher potential for re-growth of hybrids compared to Eurasian watermilfoil following treatment. Jefferson Slough hybrids may require additional treatment to achieve sufficient long-term control. In conclusion, I discuss integration of genetic surveys into management and research priorities.