A false positive food chain error associated with a generic predator gut content ELISA

Authors: Hagler, James

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2016
Publication Date: 12/1/2016
Citation: Hagler, J.R. 2016. A false positive food chain error associated with a generic predator gut content ELISA. Entomologia Experimentalis et Applicata. 161(3):187-192.

Interpretive Summary: Knowledge of arthropod predation is an important component of a successful integrated pest management program. Perhaps the most popular indirect method to assess predation is by examination of a predator’s stomach contents for the presence of prey (usually a targeted pest) DNA. However, pest-specific DNA assays are prone to yielding food chain errors. That is, it is possible that pest remains can pass through the food chain as the result of a higher order predator consuming a lower order predator (a primary predator) that had previously consumed the pest of interest. If so, the primary predator would be abolished from the ecosystem and, in turn, the secondary predator would be erroneously credited for providing the biological control services on that pest. A generic gut assay was developed by an ARS scientist at Maricopa, AZ that proved to be more cost-effective, versatile, and reliable at detecting prey remains in lower order predators than the DNA assay technique. The present study examined the proclivity of obtaining a food chain error with the generic assay. Data revealed that the generic assay was 100% accurate at detecting protein-marked prey remains in the guts of lower order predators. However, the assay is also yielded a high frequency of food chain errors for the higher order predators that consumed a lower order predator. These findings begin to identify limitations of the molecular gut content analysis approach for studying insect predation.

Technical Abstract: Conventional prey-specific gut content ELISA and PCR assays are useful for identifying predators of insect pests in nature. However, these assays are prone to yielding certain types of food chain errors. For instance, it is possible that prey remains can pass through the food chain as the result of a secondary predator (hyperpredator) consuming a primary predator that had previously consumed the pest. If so, the pest-specific assay will falsely identify the secondary predator as the organism providing the biological control services to the ecosystem. Recently, a generic gut content ELISA was designed to detect protein-marked prey remains. That assay proved to be less costly, more versatile, and more reliable at detecting primary predation events than a prey-specific PCR assay. This study examines the proclivity of obtaining a “false positive” food chain error with the generic ELISA. Data revealed that the ELISA was 100% accurate at detecting protein-marked Lygus hesperus Knight remains in the guts of two primary predators; Hippodamia convergens Guerin-Meneville and Collops vittatus (Say). However, there was also a high frequency (70%) of food chain errors associated with hyperpredators (Zelus renardii Kolenati) that consumed a primary predator that possessed protein-marked L. hesperus in its gut. These findings serve to alert researchers that the generic ELISA is also susceptible to food chain errors.