Toward Repurposing Global Passive Air Sampling Networks for Insect Monitoring: Promises and Pitfalls of Airborne eDNA

ABSTRACT Insects are crucial for ecosystem functioning and provisioning services, yet the study of their decline is hampered by traditional monitoring systems. Airborne eDNA has the potential to help monitor the rapid changes insect communities are experiencing. Polyurethane foam passive air samplers (PUF‐PAS) are widely deployed to monitor environmental pollutants, yet their capacity to capture biological signals such as environmental DNA (eDNA) remains largely unexplored. Recent advances in airborne eDNA research create a timely opportunity to evaluate PUF‐PAS as a tool for biodiversity monitoring and to leverage existing global sampling networks for conservation. Focusing on insects, we assess whether PUF‐PAS can provide eDNA‐based biodiversity data comparable to those obtained with traditional sampling methods. We compared the taxonomic richness, community composition, and detection biases of PUF‐PAS to a conventional method for sampling flying insects, Malaise traps. We deployed both samplers across Montreal, Canada, during the entire flight season and collected 49 samples of each method. Insect communities were characterized at the order level using morphological identification (Malaise traps) and DNA metabarcoding (PUF‐PAS). Insect communities collected with both methods showed substantial overlap, with 11 insect orders detected by both methods; 3 were unique to Malaise traps and 1 to PUF‐PAS. On average, estimates of insect abundance from Malaise traps were strongly positively associated with PUF‐PAS detection probability and read counts. However, PUF‐PAS detection probability and read counts were best explained by Malaise trap counts measured several weeks prior and integrated over approximately 8 weeks, indicating a delayed biological signal. Our results suggest that PUF‐PAS is better suited for interannual monitoring of common insect taxa, particularly for detecting broad temporal trends. Given the availability of global passive air sampling infrastructure, this approach not only has strong potential for large‐scale biodiversity monitoring but also could foster interdisciplinary collaborations between environmental toxicologists and biodiversity scientists.