A molecular approach to unravel trophic interactions between parasitoids and hyperparasitoids associated with pecan aphids.

Advances in molecular ecology can overcome many challenges in understanding host-parasitoid interactions. Genetic characterization of the key-players in systems helps to confirm species and identify trophic linkages essential for ecological service delivery by biological control agents; however, relatively few agroecosystems have been explored using this approach. Pecan production consists of a large tree perennial system containing an assortment of seasonal pests and natural enemies. As a first step to characterizing host-parasitoid associations in pecan food webs, we focus on aphid species and their parasitoids. Based on DNA barcoding of field-collected and reared specimens, we confirmed the presence of 3 species of aphid, one family of primary parasitoids, and 5 species of hyperparasitoids. By applying metabarcoding to field-collected aphid mummies, we were able to identify multiple species within each aphid mummy to unravel a complex food web of 3 aphids, 2 primary parasitoids, and upward of 8 hyperparasitoid species. The results of this study demonstrate that multiple hyperparasitoid species attack a single primary parasitoid of pecan aphids, which may have negative consequences for successful aphid biological control. Although further research is needed on a broader spatial scale, our results suggest multiple species exist in this system and may suggest a complex set of interactions between parasitoids, hyperparasitoids, and the 3 aphid species. This was the first time that many of these species have been characterized and demonstrates the application of novel approaches to analyze the aphid-parasitoid food webs in pecans and other tree crop systems.