Recent advances in sociogenomics allow for comparative analyses of molecular mechanisms regulating the development of social behavior. In eusocial insects such as ants, one aspect of their sociality, the division of labor, has received the most attention. A key question is how do ant workers in a nest organize all of their necessary behaviors or tasks when no single ant is in control? The answer lies in a mechanism that is very similar to the one we use to organize our own daily activities - an internal molecular rhythm generator called the circadian clock. The goal of this project is to characterize the genetic structure of the ant circadian clock and study the evolution, development, and function of task-specific circadian rhythms in harvester ants, Pogonomyrmex occidentalis. The expression patterns of the five principle clock genes will be analyzed in field and laboratory colonies of harvester ants in order to determine when circadian rhythms and clock function develop in harvester ants and to explore how genes that regulate circadian rhythms are associated with specific tasks. The results will shed light on how evolutionary history and environmental factors influence a molecular mechanism that regulates rhythmic behavior. Because the circadian clock is conserved across diverse taxa, ranging from ants to mice to humans, the work will have an impact on our general understanding of the role of molecular clocks in the synchronization of animal behavior with the external environment. In addition, the project will provide interdisciplinary research opportunities for underrepresented students and introduce undergraduates to cutting-edge techniques in genomic and behavioral research. Finally, this project provides an ideal platform for public outreach efforts to communicate evolutionary and behavioral research because people can easily relate to the topic of circadian rhythms, for example, as it relates to jetlag.
The main goal of this project was to characterize the structure of the ant circadian clock and study the evolution, development and function of task-specific circadian rhythms in ants. We identified, sequenced and characterized the eight principle clock genes in ants: period, cycle, clock, cryptochrome, timeout, vrille, pdp & clockwork orange. The fire ant genome contains copies all of the core circadian clock genes with the notable exception of Timeless (Tim1). We performed phylogenetic analysis of 7 ant species, Nasonia, the parasitic wasp, and other insect species to show that ant clock genes are most similar to bees, another social insect. The structure and expression patterns of bee and ant clock genes are more similar to mammals than to other insects. Preliminary analysis of the molecular evolution of clock genes across social insect species revealed high variability in the sequences of these genes. We also compared the expression of two major clock genes, period and cycle, in ants that perform different behavioral tasks in both field and laboratory colonies and have discovered that there are differences in patterns of expression of clock genes in different task groups; ants that forage outside the nest have robust daily oscillations in their clock genes but ants inside the nest do not. We designed and tested a novel method of measuring ant locomotor activity using infrared lasers. The results of our experiments have shown differences in circadian rhythms depending on social environment and behavioral tasks in ants. Based on all of the above findings, we propose that the molecular clockwork in the ant is similar to the honeybee and Nasonia, suggesting that Hymenopterans may have circadian clocks that are more similar to mammalian clocks than to Drosophila and other insect clocks. In addition, we have shown that the ant circadian clock is linked to the behavioral division of labor in ants. In terms of education and training, this project has trained two research assistants/technicians and thirteen undergraduates in the following techniques; field collections, brain dissection, RNA extraction and purification, DNA extraction and purification, PCR, gel electrophoresis, qPCR and expression analyses, bioinformatic analyses, DNA sequencing, phylogenetic analyses, confocal microscopy and 5’, 3’ RACE procedures. We developed an ‘Ant Day’ at the local preschool and elementary school with undergraduates organizing hands-on activities including bug collecting and identification, diversity displays using Colgate University’s insect collections, interactive computer games, amazing ant videos, and design & color bug pictures. This research project was also incorporated into a community based learning class for undergraduates in environmental science education. As part of this class, students designed and built a nature/science center in an old barn for the local nursery and pre-K schools to use.
