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Discipline: Biological Sciences
Subcategory: Ecology
Session: 1
Room: Exhibit Hall A
Amber Guerra - Glendale Community College
Co-Author(s): Jefferey Wood, Hawaii Community College, Hawaii; Tia Harrison, University of Toronto, Toronto
Mutualisms exist between two different species as a symbiotic relationship that evolves to increase survivorship of both partners. We studied the relationship between the extrafloral nectar bearing Chamaecrista nictitans and different ant species in Costa Rica. The nectar secreted by the plant is a food source for the ants and in return the ants protect the plant against herbivory. I aimed to test the hypothesis that higher ant visitation provides plants with better protection against herbivory. Previously, this hypothesis was tested in temperate New Jersey and the results of that study indicated that ant visitation did not deter predation on the plant (Ruhen 2003). However we expected to find that ant visitors are mutualists in Costa Rica because the enriched tropical environment provides a broader range of both ant species and herbivores. From June to August 2019, natural surveys and a manipulative experiment were conducted in the biodiverse tropical environment of Costa Rica. During the natural surveys, we visited plants and tallied the total number of ants on the plant to assess ant visitation and counted the number of leaves damaged on the plant to assess herbivory levels. We then regressed ant visitation against herbivory using linear models in R (version 1.2.1335). On a random subset of plants, we applied tanglefoot to prevent ants from accessing plants. We counted the number of leaves damaged by herbivores on the tanglefoot plants and control plants (no tanglefoot) and compared the two groups using ANOVA tests in R (version 1.2.1335). We found a significant correlation between ant visitation and the level of herbivory in the natural surveys (P < 0.05). Our manipulative experiment showed that ant-excluded plants experienced higher levels of damage during the experiment compared to control plants. These results imply that the relationship between ants and C. nictitans plants is mutualistic and that ant visitation effectively reduces herbivory damage and improves the plants overall fitness. As more clarity is gained on this type of mutualistic relationship, what may be more impactful is how changes to the environment and changes within these ecosystems can affect the relationships themselves. The study in New Jersey didn?t show significance between ant presence and herbivory levels, but in our study in the diverse tropics, the ants played a positive role in the plants survivorship (Ruhren 2003). Future studies that can measure the nectar concentration in the plant in relation to ant presence and herbivory levels may further clarify the significance of the nectaries (Mondor 2006). References: Mondor, E.B., Tremblay, M.N. and Messing, R.H. 2006. Extrafloral nectary phenotypic plasticity is damage- and resource- dependent in Vicia faba. Biology letters, 2, 583-585. Ruhren, S. 2003. Seed predators are undeterred by nectar-feeding ants on Chamaecrista nictitans (Caesalpineaceae). Plant Ecology, 166: 189-198.
Funder Acknowledgement(s): We thank the Organization Tropical Studies and Research Experience for Undergraduates (REU) for funding the research. This research was conducted under the Scientific Research Permit Number: SINAC-PNI-ACLAP-018-2019.
Faculty Advisor: Tia Harrison, tia.harrison@mail.utoronto.ca
Role: I designed and conducted the field research project during the 2019 OTS REU program in Costa Rica. With guidance from my field mentor, I developed the field research question for the project. I designed the manipulative experiment and natural survey criteria and presented my research proposal to a mentor panel. After approval, I collected data on plant herbivory and ant observations and once completed, I managed and analyzed field data using R and RStudio programs. I presented my findings at the end of the REU program at the Organization for Tropical Studies Research Symposium.
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