Removing external DNA contamination from arthropod predators destined for molecular gut-content analysis

Authors

  • MATTHEW H. GREENSTONE,

    1. United States Department of Agriculture, Agricultural Research Service, Invasive Insect Biocontrol and Behavior Laboratory, Beltsville, MD 20705, USA
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  • DONALD C. WEBER,

    1. United States Department of Agriculture, Agricultural Research Service, Invasive Insect Biocontrol and Behavior Laboratory, Beltsville, MD 20705, USA
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  • THOMAS A. COUDRON,

    1. United States Department of Agriculture, Agricultural Research Service, Biological Control of Insects Research Laboratory, Columbia, MO 65203, USA
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  • MARK E. PAYTON,

    1. Department of Statistics, 301 MSCS Building, Oklahoma State University, Stillwater, OK 74078, USA
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  • JING S. HU

    1. United States Department of Agriculture, Agricultural Research Service, Invasive Insect Biocontrol and Behavior Laboratory, Beltsville, MD 20705, USA
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Matthew H. Greenstone, Fax: 301 504 5104; E-mail: matt.greenstone@ars.usda.gov

Abstract

Ecological research requires large samples for statistical validity, typically hundreds or thousands of individuals, which are most efficiently gathered by mass-collecting techniques. For the study of interspecific interactions, molecular gut-content analysis enables detection of arthropod predation with minimal disruption of community interactions. Field experiments have demonstrated that standard mass-collection methods, such as sweep netting, vacuum sampling and foliage beating, sometimes lead to contamination of predators with nontarget 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 Leptinotarsa juncta. We then attempted to remove contaminating DNA by washing in ethanol or bleach. A 40-min wash with end-over-end rotation in 80% EtOH did not reliably reduce external DNA contamination. Identical treatment with 2.5% commercial bleach removed most externally contaminating DNA without affecting the detectability of the target prey DNA in the gut. Use of this bleaching protocol, perhaps with minor modifications tailored to different predator–prey systems, should reliably eliminate external DNA contamination, thereby alleviating concerns about this possible source of cross-contamination for mass-collected arthropod predators destined for molecular gut-content analysis.

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