Cuticular Barcoding-A Novel Method for Host Identification From Adult Parasitoid Wasps

Parasitoid wasps are important regulators of their hosts and highly relevant for the resilience of terrestrial ecosystems. However, data on parasitoid-host interactions are scarce and missing for many parasitoid species as parasitoids are mostly collected as adults without host association and rearing of parasitoids from their hosts can be difficult. Molecular methods can thus help to circumvent this bottleneck. We here present cuticular barcoding, a novel non-destructive molecular approach to identify parasitoid-host associations from adult parasitoid wasps. We tested our approach by rearing the parasitoid wasp Lariophagus distinguendus on two beetle species, and washing off remnant host DNA from the wasp cuticle to detect the host species using DNA barcoding. Our results showed a success rate of 49%, detecting the host species in 35 out of 72 samples. Samples containing pooled wasp specimens performed equally well as single wasp specimens, which indicates that single field-collected wasps are sufficient to identify host associations. Hosts could be detected in wasps that were fixated either through freezing or ethanol, which also supports the application of this method in the field. The primers Jerry/Pat targeting the mitochondrial COI gene performed better than the universal primers LCO/HCO, indicating that more studies testing universal primers are needed to establish this method. This non-destructive method allows to preserve the sampled wasp as a physical voucher for subsequent morphological identification which will be essential for its usage in situ. Our study presents a novel method that enables detection of parasitoid-host interactions, and holds significant potential for conservation ecologists, pest managers and evolutionary biologists.