The chemical composition of living organisms reflects their evolution, their traits, and the environment in which they exist. Differences in the availability of certain resources, and in particular a scarcity of a chemical resource that is critical for the expression of a particular trait, may restrict the abundance of some species. The extent to which a specific set of traits, starvation resistance, worker size, colony size, colony growth rate, and colony tempo, is linked to chemical composition and nutrient availability will be tested in a diverse community of litter ants in a lowland tropical rainforest of Panama. Experimental manipulations of particular nutrients will be used to test whether nutrient availability can shift the species composition of the ant community in ways that are consistent with observed correlations between species traits and chemical composition.
This project in tropical biodiversity science is an excellent entry point to evolutionary ecology for students, and undergraduates will participate in all phases of the research. The familiarity and experimental tractability of ants make them an ideal instructional tool, and the multiple research foci of the project will provide opportunities for students to acquire a diversity of skills. The field work, set on Barro Colorado Island in Panama, will expose students to the dynamic research culture of an international field station. Together, these experiences should provide students with the skills, knowledge, and motivation to pursue a career in science.
Natural systems such as rainforests are inherently complex. One way in which environmental scientists make progress toward understanding this complexity is by developing simplified models of reality. This simplification helps researchers to design experiments around measurable quantities. Simplification, however, can come at the cost of realism, and can sometimes keep important system features and dynamics from being discovered. Challenging simplifying assumptions in existing models is thus essential for directing scientific activity in meaningful directions. Our research project, "Toward a stoichiometric theory of ant ecology--from colony performance to community composition", aimed to introduce nutritional complexity into the study of the ecology of ants. Ants and other social insects (e.g., bees and wasps) are important to study because they make up more than half of insects in the world and have large impacts on soil conditions, herbivory, pollination, and other aspects of ecosystems. Traditionally, the study of how ants use food resources in the wild has been studied with the simplifying assumption that a single substance ("food" or "energy") is enough to assess the importance of those resources. Our work involved a series of studies aimed at demonstrating how mixtures of different food components (e.g., carbohydrates, protein, fats, minerals) affect aspects of ant colonies (such as their behavior, physiology, and structure), and the consequences of these effects for the surrounding environment. Being able to predict these consequences is essential for understanding how ants – a critical component of many ecosystems - will respond to the rapid environmental changes currently occurring. Our work was set in a New World tropical rainforest on Barro Colorado Island (BCI) in Panama. BCI was "created" by the purposeful flooding in the construction of the Panama Canal. The only permanent structures on the island are buildings associated with a field station run by the Smithsonian. Much of what we know about the biology of the New World tropics is because of research that has been done at this site. Our focus on ants in this forest makes sense because they are critical features of rainforests and have nutritionally complex diets (many collect both protein-rich foods such as insects and carbohydrate-rich nectars). We collaborated with our undergraduate students to complete multiple projects on ant nutrition between 2009 and 2012. Some research focused on exploring how the balance of dietary carbohydrates and protein affects ant colony performance. We found that increased access to carbohydrates (but not protein) increases the survival rate of workers within colonies. Surprisingly, increased carbohydrate access also allowed ants to produce secretions that they use to help nestmates resist infection by a fungus that has the potential to devastate whole colonies. This work thus showed that access to carbohydrates may be critical for allowing ants to form social groups without succumbing to communicable infection. Other projects explored how specific nutrients affect the organization of ant communities, how waste products of ants in the canopy can affect soil conditions, how nutrition and other factors affect ant tolerance to temperature extremes, and how resource use in ant colonies varies colony size and complexity. Beyond our research projects, another main achievement of the project was to provide advanced training for undergraduate scientists. We gave in-depth experiences to 12 undergraduates over the course of the project. Seven of these students spent significant time conducting research in the rainforest in Panama. Nine of the students are co-authors on published or soon-to-be-published peer-reviewed papers. Ten of the students presented their research at either a local, regional, or national meeting; many of the students presented work at multiple meetings. One student won the President’s Award for best student presentation at the Entomological Society Meeting in 2012. Four students are currently pursuing PhDs in ecology related fields, one is a full-time project manager on an ecology field project, three others have recently received their undergraduate degrees and are considering graduate school, two are in medical school, and one is in veterinary school. All of these students used their research experiences as the basis for their applications for advanced study. Several students shifted interests toward environmental science research due to their positive experience in our program. The enthusiasm generated by these students also contributed to increased professionalism in the student-directed research program in our department at the University of St. Thomas. Professional training for science students at liberal arts colleges is essential for the advancement of US science research given that most future PhD candidates start in such programs. Our project has helped to stimulate ecologists to move beyond a simplified, energy-centered model of ant ecology. We hope that a long-term consequence will be a greater ability to predict how environmental changes brought about by human activity will affect ants and other insects that impact how ecosystems function.
