Molecular technologies have emerged as powerful tools in dietary studies. Given the high sensitivity of these tools, external contamination of samples with DNA can yield false results. Yet the use of aseptic techniques under field conditions may be impractical. Invasive fire ants (Solenopsis invicta) are generalist consumers, and their liquid diets complicate dietary assessments. After amplifying the ITS2 gene region of DNA extracts obtained from whole worker ants, we used Sanger sequences of amplicons to infer plant food preferences of fire ants obtained from longleaf pine savannas.
Results/Conclusions
BLAST searches of nucleotide sequences gave mixed results. Matches in GenBank included plant taxa occurring in our longleaf sites, as well as plant taxa unlikely to occur (= noninhabitants). To rule out external contamination, we performed a decontamination study on a subset of samples matching to noninhabitants. Duplicate samples of worker ants were soaked in mango juice (“contaminated”), and half of these samples were decontaminated with 2.5% bleach. Sanger sequences of contaminated samples matched to mango (Mangifera spp.), while sequences of decontaminated samples matched to noninhabitants, but not necessarily the same taxa as in earlier results. The short lengths of amplicons (< 300 bp) in our study may have restrained taxonomic resolution. Decontamination with bleach was simple and inexpensive, and because it did not interfere with nucleotide sequencing, it should be applicable to more robust molecular technologies, such as next-generation sequencing.