DNA metabarcoding based detection of parasitoids

Many hymenopteran species are highly specialized parasitoids. These parasitoid species can inhabit different life stages of herbivore host species, be it eggs, larval states or pupae of lepidopterans. Many of these, such as the oak processionary (Thaumetopoea processionea) or the gypsy moth (Lymantria dispar), are agricultural and forest pests. By keeping the numbers of lepidopteran pests under control, parasitoid hymenopterans play a key role in maintaining ecosystem health and stability of our forests and fields. Thus, they are of great importance for the ecological equilibrium or natural balance of ecosystems.

In many parasitoid hymenopterans, little is known about host-parasite interactions. In order to better protect and detect these parasitoid species, we need a better understanding of these interactions. The classical approach to determine which parasitoid species is associated with which lepidoperan species is to rear the larvae until the adult hymenoptera hatches. This approach is time consuming and demands a high level of expertise. In many cases, even after hatching, these hymenopteran species are very difficult to classify.

DNA metabarcoding has the advantage over this classical approach of allowing the detection of parasitoid species within any stage of the host (egg, larvae or pupae). For example, an entire caterpillar, including the parasitoid, can be analyzed in one single analysis in just a few days. Rapid and reliable results achieved by DNA metabarcoding can be crucial to better protect these important regulatory species within different ecosystems. Furthermore, our technology can be used to monitor parasitization rates in order to make decisions about the ecological status and possible measures for biological pest control.

Since all animals were stored in the trap alcohol together, and since DNA metabarcoding is a very sensitive method, it detected more than just one species of lepidopterans. The species of host caterpillar and its parasitoids can reliably be determined by assessing which detected species had the highest number of reads in the sample. Thus, DNA metabarcoding allows the parasitization rate within a developmental stage of a population to be detected very quickly.