Print PageEcologists often study plant-herbivore-parasitoid food webs or their parts, both for their importance in natural and agricultural systems and relative tractability. Less attention has been paid to predators interacting with species in these food webs for the evasiveness of predation events. We show how methods based on DNA barcoding can effectively replace traditional rearing-based reconstruction of tri-trophic food webs, and, additionally, link predators to the same framework. Specifically, we investigate i) how caterpillar feeding behavior affects rates of internal parasitism by hymenopteran and dipteran parasitoids and ii) how social wasp predation on caterpillars affects parasitoids by intra-guild predation within a species-rich rainforest food web from Papua New Guinea. We employ standard DNA barcodes to sequence herbivore and parasitoid (if present) barcode marker regions from each caterpillar, and use generalized mini-barcode markers to recover plant mixtures consumed by the lepidopteran herbivore.
Results/Conclusions
We demonstrate the utility of our barcode approach to investigate herbivore diet by matching sequences recovered from caterpillar herbivores to an extensive barcode library of local plant species. We show that many species exhibit higher rates of generalized feeding than expected. Individual animals tend to only consume a single species, whereas different individuals of that species consume many species. However, we find little correlation between diet choice and rates of internal parasitism by hymenopteran parasitoids. Although we do observe higher rates of parasitism using DNA based diagnostic methods than that reported when parasitism is estimated through rearing. Lastly, we find no statistical effect of diet or rates of internal parasitism on rates of predation by social wasps.
