Discipline: Ecology Environmental and Earth Sciences
Shaquetta Johnson - Jackson State University
Co-Author(s): Thomas Harmon and Angel Fernandez Bou, University of California, Merced, CA
Atta cephalotes is a common leaf cutter ant (LCA) species dominating the Neotropics. LCA employ a complex foraging system to furnish their fungal gardens with vegetation. The fungi are essential for development of the ants’ larvae and their own sustenance. While serving the colony, LCA foraging and fungi cultivation also significantly impacts carbon cycling in the Neotropics, and potentially beyond. Research has focused on events associated with the ants foraging behavior, including reasons for the ants “hitchhikíng” on larger ants’ leaf fragments and the rhythmic foraging behavior. The primary focus of this project was to establish the vegetation input to the Atta colony and how rainfall influences their daily foraging patterns. Understanding the characteristics and amounts of vegetation entering the nests will help to establish how efficient the Atta must be to successfully furnish their fungal gardens, and what the potential carbon emissions are from those nests. By testing a fairly new method, we were able to establish ratios of vegetation collected at many trails at a nesting site of La Selva Biological Station, Costa Rica, with respect to rainfall. In order to calculate the average amount of vegetation collected at a single nesting site, we measured the velocity of ants, dry weight of vegetation, and day versus night foraging and established a formula representing the total vegetation collected over a particular time period with and without rainfall. Velocity measurements of the Atta cephalotes were compared utilizing histograms and a Tukey test revealed a significant difference with and without rainfall (p = 0.015). The dry weight of the vegetation over several days were also compared, but no significant difference between the dry mass was observed. Day versus night foraging was compared utilizing quartiles and line graphs to demonstrate the peaks of activity in a 24 hour cycle. Using the vegetation dry weight and ant velocity measurements, we estimated that the ants were carrying approximately 43 kg/month of vegetation to their nest. Future research involves understanding the effects of rainfall on foraging behavior and vegetation collection in more detail, developing an annual estimate (testing for seasonal variations), and connecting vegetation inputs with carbon dioxide emissions from the nest.
Funder Acknowledgement(s): I would like to thank my family, peers, and professor/advisor Terrence Wright at Jackson State University for supporting my endeavors to pursue an intense, biological research experience. I would also like to thank my research partner, REU students, and La Selva staff and community for their encouragement and genuine company throughout my time at the station. In particular, I would like to thank my mentor, Thomas Harmon, and his graduate student, Angel Fernandez-Bou, for their guidance and for challenging me to gain more knowledge while performing my research project. Last but certainly not least, I would like to thank the Organization for Tropical Studies for this experience of a lifetime, NSF, and LSAMP for providing the funding for this experience.
Faculty Advisor: Thomas Harmon, email@example.com
Role: I participated in the actual field study of taking measurements of the velocity of the ants, analyzing the data from the overnight sampling videos of the ants foraging activity, and assisting with measuring CO2 fluxes in the soil to determine the relevance of input versus output at the testing site.