Submitted to: Molecular Ecology Resources
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/2/2011
Publication Date: 1/24/2012
Citation: Greenstone, M.H., Weber, D.C., Hu, J.S., Coudron, T.A., Payton, M.E. 2012. Removing external DNA contamination from arthropod predators destined for molecular gut-content analysis. Molecular Ecology Resources. 12(3):464-469. Interpretive Summary: Predatory natural enemies kill millions of insect pests, thereby reducing insecticide use and crop losses. Molecular gut-content analysis is a powerful technology for studying the feeding behavior of predators, but it is subject to error due to contamination by molecular material from other insects during collection. To deal with this problem, we performed experiments in which predators with known feeding history were deliberately contaminated with material from insects that were not consumed. We found that a 40-minute soak in a dilute solution of commercial bleach effectively removed externally contaminating DNA from predators without affecting the ability to detect DNA of the target prey in the predators’ guts. These results will be used by scientists to ensure that feeding assays of predators collected during field research are not compromised by contamination in the course of collection, thereby helping to determine which species are most effective in controlling insect pests, and hence most worthy of conservation by crop management practices.
Technical Abstract: Molecular gut-content analysis enables detection of arthropod predation with minimal disruption of ecosystem processes. Field and laboratory experiments have demonstrated that mass-collection methods, such as sweep-netting, vacuum sampling, and foliage beating, can lead to contamination of fed predators with non-target DNA, thereby compromising resultant gut-content data. We deliberately contaminated immature Coleomegilla maculata and Podisus maculiventris that had been fed larvae of Leptinotarsa decemlineata by topically applying homogenate of the alternate prey L. juncta. We then attempted to remove contaminating DNA by soaking in ethanol or bleach. A 40-min soak with rotation in 80% EtOH did not reliably reduce external DNA contamination. Identical treatment with 2.5 % commercial bleach removed externally contaminating DNA without affecting the detectability of the target prey DNA in the gut. Use of this bleaching protocol, perhaps with minor modifications depending on the predator-prey system, should reliably eliminate external DNA contamination, freeing investigators to use conventional methods for mass collection of arthropod predators for molecular gut-content analysis.