DISSERTATION RESEARCH: Plastic Worker lifespan and the influence of demand, demography and death on labor economics in the Florida harvester ant (Pogonomyrmex badius)

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Although a social insect colony may persist for decades, the sterile workers within it may live only a fraction of a year. Much like cells in a body, the rate at which workers in a colony senesce should trace the lifespan imposed on them by their environment. If the death rate in their environment is high, selection for inexpensive, short-lived, "disposable" workers is predicted. In workers of the Florida harvester ant (Pogonomyrmex badius), a 5-fold difference in the rate of cuticle darkening, age at first foraging and lifespan occurs seasonally. When removed from field mortality factors, longevity in both types of workers increases greatly, indicating that an individual's potential lifespan is much greater than its realized lifespan. In social insects, differences in larval nutrition often yield adults of different size and correlated characteristics, but in adults of identical body size (as in P. badius), factors influencing longevity are less clear. This study will investigate how development rate and longevity are influenced by colony production of workers with two distinct lifespans and behavioral trajectories. To do so, feeding profile, metabolic rate, fat content and queen investment will be compared for short-lived summer workers and long-lived autumn workers in normal and reciprocal environmental conditions. These findings will help untangle how division of labor is related to developmental-age in social insects, and how selection has shaped labor allocation by acting on worker development rate. These findings will help illuminate lifespan plasticity and regulation of aging across biological hierarchies. It may also challenge the perception of foragers in social insects as physiologically depleted and disposable. By engaging students of all ages in meaningful work in a local ecosystem, this project will also support public understanding of science and increase awareness of the unique and charming inhabitants of the Apalachicola National Forest. The data from this study will be stored electronically at The Florida State University in Tallahassee Florida, and will be available upon request.