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SFS Annual Meeting

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NUTRIENT SUBSIDIES RESULT IN LARGER BODY SIZE, NOT ALTERED STOICHIOMETRY

Human activities create novel nutrient gradients in freshwater ecosystems. These streams represent a gradient of phosphorus and nitrogen enrichment which results in a subsidy gradient in basal resources. Mature nymphs of Ephemeroptera (mayflies) and adult Coleoptera (beetles) and Hemiptera were sampled from streams in central Texas. Organisms did not respond to the subsidy gradient by altering their body stoichiometry, but rather by increasing body size across the gradient. Overall, females showed the greatest increase in body size relative to males of the same species. The positive correlation between body size and fecundity in insects is strong. The increase in egg production may be influencing community structure at enriched sites. Phylogenetic patterns in body stoichiometry are evident (especially in mayflies) and are related to life history characteristics.

Jeffrey A. Back (Primary Presenter/Author), Baylor University, Jeff_Back@baylor.edu;