eDNA on the go: a direct comparison of fixed and vehicle mounted airborne eDNA sampling methods for terrestrial vertebrate species detection at large spatial scales

Air is receiving increasing recognition as a biologically rich source of taxonomically diverse environmental DNA (eDNA). Multiple proof-of-concept studies have explored air as a medium for the detection of single terrestrial species, and even entire terrestrial communities, including mammals, non-anemophilous plants and insects. Airborne eDNA has been sampled using various stationary devices but if we can access it using mobile collection methods, we can rapidly assess biodiversity at large spatial scales. We therefore compared passive eDNA filters deployed for short (30 mins) and long periods (24 hrs) with filters attached to cars that sampled transects through natural and human-modified environments. Our metabarcoding procedure detected 49 vertebrate taxa (33 birds, 15 mammals and 1 amphibian) from all three eDNA air sampling approaches combined, with 29 of these taxa detected in samples collected using the mobile method. The total number of taxa, or proportions of unique taxa detected, did not differ by sampling method, land use or day. Community composition was not significantly impacted by sampling method or sampling day but differed significantly between land uses. We propose that our car-mounted air eDNA sampler could be a game changer for large scale, rapid biomonitoring efforts.