Analysis of single‐copy,nuclear microsatellite markers from flies collected on sticky traps

Sticky traps can provide large numbers of spatially referenced samples for use in molecular ecological studies of insects. However, the adhesives used on these traps, and the methods used to clean adhesive off trapped individuals, could potentially interfere with downstream molecular analyses. Specimens captured on sticky traps have been successfully used to analyse mitochondrial or multiple‐copy ribosomal DNA markers, but not single‐copy nuclear markers. Furthermore, the effects of trap adhesive and cleaning protocol on the success of molecular analyses have not been explored. Here, we examine the effects of trap adhesive, sample cleaning method, and sample storage condition on DNA concentration and purity, and on the ability to amplify single‐copy, nuclear microsatellite loci, using specimens of the western cherry fruit fly, Rhagoletis indifferens (Diptera: Tephritidae) captured on sticky traps in an orchard. We could extract DNA of high purity, and amplify microsatellite loci in multi‐plex polymerase chain reaction (PCR), under all combinations of treatments. However, DNA yield, DNA purity and the yield of PCR products were affected by treatment, with complex interactions among trap adhesive, sample cleaning method, and storage condition. Samples that were cleaned with acetone and stored dry had the highest DNA concentration. With respect to PCR amplification, samples cleaned with Histo‐clear produced much less product than those cleaned with acetone or not cleaned at all, whereas samples that were stored dry produced more PCR product than samples stored in ethanol. Insects captured on sticky traps can thus provide genetic data appropriate for molecular ecological analyses under a wide range of treatment conditions. However, potential interactions among adhesives, cleaning protocols and storage conditions suggest that any novel combination for treatment of samples from sticky traps should be tested on a small scale prior to collecting large numbers of samples for genetic studies.