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United States Department of Agriculture

Agricultural Research Service

Research Project: CRANBERRY GENETIC IMPROVEMENT AND INSECT PEST MANAGEMENT

Location: Vegetable Crops Research Unit

Title: Trophic spectra under the lens of amino acid isotopic analysis

Authors
item Steffan, Shawn
item Chikaraishi, Yoshito -
item Horton, David
item Miliczky, Eugene
item Zalapa, Juan
item Jones, Vincent -
item Ohkouchi, Naohiko -

Submitted to: Entomological Society of America Annual Meeting North Central Branch
Publication Type: Abstract Only
Publication Acceptance Date: January 27, 2014
Publication Date: March 9, 2014
Citation: Steffan, S.A., Chikaraishi, Y., Horton, D.R., Miliczky, E., Zalapa, J.E., Jones, V., Ohkouchi, N. 2014. Trophic spectra under the lens of amino acid isotopic analysis [abstract]. Entomological Society of America Annual Meeting North Central Branch.

Technical Abstract: Recent advances in compound specific isotopic ratio analysis (CSIRA) have allowed researchers to measure trophic fractionation of 15N in specific amino acids, namely glutamic acid and phenylalanine. These amino acids have proven useful in food web studies because of the wide and consistent disparity in their respective fractionation tendencies. In controlled feeding trials, we used CSIRA to confirm the accuracy of the Chikaraishi C3-plant equation for trophic levels 1 through 4. We then collected wild arthropods from an old-field site, and each specimen was analyzed using both the Chikaraishi method and the conventional bulk-15N method. Regression analysis characterized the relationship between these two methods, allowing us to convert bulk-15N values into trophic level estimates (among the many specimens not analyzed via CSIRA). This approach facilitated greater sample sizes and thereby permitted investigations of trophic spectra and functional diversity. We show that species often thought to be strict herbivores were true omnivores, and certain carnivore species were actually pests of crop production. Thus, our study is the first to reveal which species are likely to be beneficial for crop protection, and which are not.

Last Modified: 9/1/2014
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