Assessing risks of Wolbachia DNA cross-specimen contamination following mass collection and ethanol storage

Wolbachia and other intracellular bacteria that manipulate reproduction are widespread and can have major consequences on the ecology and evolution of their hosts. Several studies have attempted to assess the host range of these bacteria based on polymerase chain reaction assays on material preserved and collected using a variety of methods. While collecting in the field, mass storage in ethanol before sorting specimens in the laboratory is by far the easiest technique, and an integral component of Malaise trapping. This implicitly relies on the assumption that mass ethanol storage does not produce cross-contamination of Wolbachia DNA among specimens. Here we test this assumption. The absence of cross contamination between known positive and negative samples stored within a vial indicate there is no reason to believe collective storage of specimens creates artefactual increases in the incidence of Wolbachia or other intracellular bacteria.