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United States Department of Agriculture

Agricultural Research Service


Location: Vegetable Crops Research

Title: Beneficial or not? Carnivore trophic position under the lens of amino acid isotopic analysis

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
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2014
Publication Date: 11/18/2014
Citation: Steffan, S.A., Chikaraishi, Y., Horton, D.R., Miliczky, E., Zalapa, J.E., Jones, V., Ohkouchi, N. 2014. Beneficial or not? Carnivore trophic position under the lens of amino acid isotopic analysis [abstract]. Entomological Society of America Annual Meeting. Paper No. 1420.

Interpretive Summary:

Technical Abstract: The trophic tendency of a carnivore shapes the nature of its contribution to herbivore suppression, as well as its indirect role in crop protection. Unfortunately, measuring the lifetime trophic tendency of a carnivore has remained prohibitively difficult, and as a result, animal trophic function has often been classified within a broad scheme of overly general categories, such as “omnivore” or “carnivore.” Because carnivory often involves intraguild predation, there is the potential for enemy species to reduce carnivore populations more than herbivores, effectively releasing pest species from population control. To provide greater resolution of trophic tendency within agricultural contexts, we used novel isotopic approaches to measure degrees of carnivory among consumer species. We analyzed the 15N:14N ratios of specific amino acids (phenylalanine and glutamic acid) within target organisms, and incorporated these data into a system-specific trophic position formula. This formula generated accurate trophic position estimates representing the lifetime trophic tendencies of species. The trophic position estimates were then regressed against bulk-15N data to correlate amino acid isotopic analysis with bulk-15N data, which in turn allowed for trophic position estimation using bulk-15N data. Using the frequency distributions of the trophic position estimates, we present the trophic spectrum of each species arrayed across “trophoclines.” Species traditionally thought to be herbivorous were actually quite omnivorous, while certain carnivorous species were shown to be both intraguild predators and functional pests of the crop. Our findings reveal the degree to which free-roaming carnivore populations contribute to herbivore suppression, and thus, which species are likely beneficial for crop protection.

Last Modified: 10/17/2017
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