Manuel Stothut, Damaris Kühne, Vanessa Ströbele, Lisa Mahla, Sven Künzel, Henrik Krehenwinkel

• Environmental DNA (eDNA) metabarcoding promises to be a cost- and time-efficient monitoring tool to detect interactions of arthropods with plants. However, observation-based verification of the eDNA-derived data is still required to confirm the reliability of those detections, i.e., to verify whether the arthropods have previously interacted with the plant. Here, we conducted a comparative analysis of the performance of eDNA metabarcoding and video camera observations to detect arthropod communities associated with sunflowers (Helianthus annuus, L.). We compared the taxonomic composition, interaction type, and diversity by testing for an effect of arthropod interaction time and occupancy on successful taxon recovery by eDNA. We also tested if prewashing of the flowers successfully removed eDNA deposition from before the video camera recording, thus enabling a reset of the community for standardized monitoring. We find that eDNA and video camera observations recovered distinct communities, with about a quarter of the arthropod families overlapping. However, the overlapping taxa comprised ~90% of the interactions observed by the video camera. Interestingly, eDNA metabarcoding recovered more unique families than the video cameras, but approximately two-thirds of those unique observations were of rare species. The eDNA-derived families were biased toward plant sap-suckers, showing that such species may deposit more eDNA than, for example, transient pollinators. We also find that prewashing of the flower heads did not suffice to remove all eDNA traces, suggesting that eDNA on plants may be more temporally stable than previously thought. Our work highlights the great potential of eDNA as a tool to detect plant-arthropod interactions, particularly for specialized and frequently interacting taxa.