DISSERTATION RESEARCH: Sodium availability and the structure of brown food webs

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

Sodium (Na) is an essential nutrient relatively unimportant for plants but critical for animal neural function, reproduction and development. However, environmental Na-availability decreases as the distance from an ocean increases. Na is constantly lost through excretion and must constantly be consumed to maintain a Na-balance. Organisms feeding low in food chains, such as herbivores, obtain little Na from their diet whereas predators consume salty diets of prey. As such, strict herbivores often suffer in Na-poor, landlocked environments (ca. 80% of earth's surface). Since Na concentration in living tissue increases from plants to predators, animals themselves are an abundant source of Na in any environment. The proposed fieldwork tests the hypothesis that omnivores (organisms that consume both plants and animals) maintain a Na-balance by consuming proportionally more animals when Na is rare. This study tests this hypothesis by sampling ants at paired coastal-inland (Na-rich vs. Na-poor) sites from Georgia to Maine, USA. Ants are ideal to assess species- and location-specific food chain position because they are ubiquitous and mainly omnivorous. The lab component of this study further tests this hypothesis through direct experimentation. Here, ant colonies will be fed diets only differing in Na content to determine the extent to which Na-hunger and predation can be induced. The results of this project may generate a new source of theory governing the diets of omnivorous species. This study will facilitate the professional development of an undergraduate through supervised field research and training in scientific communication. The participating undergraduate will help conduct the experiment, learn to manage data and identify ca. 100 species of ants. Additionally, the undergraduate assistant will have the opportunity to communicate the results of this study through presentations at local and national meetings and earn co-authorship on publications. Finally, the proposed study will generate geographically explicit data for ant species over ca. 15 degrees in latitude along Eastern North America. Vouchers from this study will be deposited in the Sam Noble Museum of Natural History (Norman, OK) and author's collections and thus available for future research.