Submitted to: Methods in Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2015
Publication Date: 12/15/2015
Citation: Hagler, J.R., Blackmer, F., Spurgeon, D.W. 2015. Accuracy of a prey-specific DNA assay and a generic prey-immunomarking assay for detecting predation. Methods in Ecology and Evolution. 6(12):1426-1434. doi: 10.1111/2041-210X.12436.
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 DNA, which is a chemical marker unique to the prey species. An alternative is to use an immunological assay to detect a unique protein marker applied to the prey and subsequently transferred to the predator during feeding. ARS scientists at Maricopa, AZ showed for a range of predator species that the immunological assay was as effective as the DNA assay for detecting predation. Moreover, the immunological assay was less expensive, less time consuming, and easier to use than the DNA assay. Further refinement of protein marking techniques for predation studies will provide a valuable and widely-available method to facilitate large-scale screening of predators for pest remains.
Technical Abstract: 1. Predator gut examinations are useful for detecting arthropod predation events. Here, the accuracy and reproducibility of two different types of gut assays are tested on various predator species that consumed an immature lacewing, Chrysoperla carnea (Stephens), that was externally labelled with rabbit immunoglobulin (IgG) protein. 2. Each individual predator homogenate was examined in triplicate for prey remains by both a conventional PCR assay to detect for C. carnea DNA and a generic ELISA to detect for rabbit IgG marked prey. The ability of each method (ELISA, PCR) to detect predation over time was compared among predators and between assay types were determined using a novel three-dimensional contingency table approach. 3. Both assay types reliably detected prior predation (e.g., at least one of the three sub-samples yielded a positive reaction) for 6 to 12 h after feeding. However, the generic ELISA was more reproducible (e.g., all three sub-samples yielded the same outcome) than the PCR. 4. This shows that it was important to assay the predators in triplicate by PCR to avoid a high occurrence of false negative reactions. Conversely, reproducible results from the ELISA procedure were not dependent on duplicate sub-samples. Overall, the generic immunomarking gut assay procedure proved an effective method to assess predation and can be easily modified to study a wide variety of predator --prey interactions.