Master of Science (MSc)
Faculty of Science
Dr. Mihai Costea
Dr. Kevin Stevens
Scarlet Ammannia (Ammannia robusta) is an annual emergent wetland plant of the Lythraceae family. Throughout most of its distribution, the species population is stable under present conditions. However, this is not the case in Canada, where A. robusta is considered endangered with only a few small populations documented in British Columbia and Ontario. In response, a recovery strategy was created for A. robusta outlining the lack of information on the species biology and ecology, with a primary objective to assess the populations in Ontario and gain information on what may be contributing to the species rarity. To assess the population status of A. robusta in Southwestern Ontario, a series of vegetation surveys and seed bank assays were conducted in historically populated or newly identified suitable areas in Essex County during 2016, 2017, and 2018 growing seasons. Although A. robusta was not seen in all historic locations, seed bank studies revealed its presence in all but one of the historic locations. The number of seedlings germinating from soil cores ranged from 0.04 ± 0.02 to 1.14 ± 0.42 seedlings per cm2. To evaluate the interaction between A. robusta and its neighbouring species, field and greenhouse trials were conducted to test the hypothesis that the number of A. robusta plants and their above- and below-ground biomass would increase with the removal of competition. However, these comparisons were inhibited by the lack of seed germination. Additionally, germination trials were conducted in a growth chamber to determine the effects of light intensity (% full light), light duration (daylight hours), or temperature (°C) on A. robusta germination. It is hypothesized that the percentage of A. robusta seeds germinating will increase with increasing light intensity, duration, and temperature. The results showed that light duration, and the interaction between light intensity and the number of weeks, had significant effects on A. robusta germination. The percentage of seeds germinating increased with an increase in light intensity (100% full light) and light duration (up to 15 hours of daylight). The interaction between temperatures and sampling days were also observed to have significant effects on A. robusta germination. Ammannia robusta’s minimum, maximum, and optimal temperature requirements were observed to be 10/5 to 15/10, 40/35 to 35/30, and 20/15°C, respectively. The results do not support the view that A. robusta germination is limited by light or temperature in the field since both requirements for germination are satisfied at most sites. Based on the results, we believe that since A. robusta is prevalent in the seed bank where it occurs, but seeds exhibit low rates of germination, other factors must impede seedling establishment. Future research and management treatments focussed on assessing such factors, including the effects of invasive species on A. robusta germination, combined with consistent monitoring programs, will assist in finding the proper mitigation plans to improve A. robusta’s distribution.
Salive, Kayla, "Assessing threats and mitigation for Scarlet Ammannia (Ammannia robusta) in Southwestern Ontario" (2020). Theses and Dissertations (Comprehensive). 2309.