Showcase of Undergraduate Research and Creative Endeavors (SOURCE)

Diet Analysis of Juvenile Dragonflies Using Group-Specific Polymerase Chain Reaction

Aquatic food webs are complex, and understanding interactions in these food webs can give an indication of ecosystem health and stability, as well as movement of energy and nutrients through ecosystems. Previous studies have utilized both microscopic gut content analysis and stable isotopes to aid in constructing food webs in these ecosystems. However, gut content analysis is time-consuming, stable isotope analysis can be cost prohibitive, and both methods only identify general categories of food items. The application of newer, molecular-based approaches has the potential to provide previously unavailable taxonomic resolution in aquatic food webs (i.e., who is eating whom?). DNA-based methods have been used in other disciplines for diet analyses, but have not been widely applied in freshwater ecology. We collected juvenile dragonflies (Odonata, Anisoptera) from Winthrop Lake in Rock Hill, South Carolina, dissected gut contents, and extracted DNA from individuals in three genera. We amplified DNA via PCR, using group-specific primers targeting mitochondrial CO1 gene regions for midges (Diptera, Chironomidae) and mosquitoes (Diptera, Culicidae) to identify these potential prey in gut contents; we used gel electrophoresis as a presence/absence test for DNA from these prey groups. Occurrence of prey groups in gut contents varied by individual and by genus of dragonfly examined. With further refinement, these methods have the potential to provide previously unavailable detail on predator—prey interactions in these ecosystems.