Eurasian frogs-bit, Hydrocharis morsus-ranae L. is a nonnative, invasive, free-floating freshwater macrophyte first deliberately introduced into Ottawa, Canada in 1932. Although the introduction, escape, and subsequent spread in North America are unusually well-documented for this invasive species, there is little information about its ecology, impacts, and management options. The purpose of this research was to examine the ecology of H. morsus-ranae in wetlands of the upper St. Lawrence River, specifically to better understand factors influencing its abundance across different wetland zones and whether a native semi-aquatic lepidopteran that was frequently associated with the plant could serve as a potential biocontrol agent. A wetland vegetation survey revealed that H. morsus-ranae is one of the most dominant species in these first- and second-order tributaries, but its presence does not appear to have any relationship with native species richness or diversity. A field study of H. morsus-ranae conducted in tributaries and embayments of the upper St. Lawrence River suggests that this species is a successful generalist that exhibits variations in productivity, resource allocation, morphology, and reproduction. This variability likely aids its ability to establish in different wetland habitat zones (robust emergent, floating vegetation, floating-leaved vegetation) that occur along water depth and light gradients. Hydrocharis morsus-ranae can be categorized as a competitive, ruderal, and stress-tolerant species in wetlands, based on Grime’s C-S-R life strategy model. A controlled, 3x3 factorial experiment was conducted to separate the effects of light and water depth on productivity and fitness of individual H. morsus-ranae plants. It revealed that there were interactions between the two factors and that under some light conditions, water depth was the stronger driver in plasticity and life history strategies. The information gathered for this dissertation provides a better understanding of the role of light and depth on performance of H. morsus-ranae and the potential use of a native insect for biocontrol. Findings may prove useful in developing management strategies for this invasive plant.
|Advisor:||Leopold, Donald J., Farrell, John M.|
|Commitee:||Parry, Dylan, Scanga, Sara E., Schulz, Kim|
|School:||State University of New York College of Environmental Science and Forestry|
|Department:||Environmental & Forest Biology|
|School Location:||United States -- New York|
|Source:||DAI-B 78/11(E), Dissertation Abstracts International|
|Keywords:||Aquatic plants, Free-floating plants, Freshwater macrophytes, Hydrocharis morsus-ranae, Invasive plants, Invasive species, New York|
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