Temporal persistence of vertebrate airborne environmental DNA in a natural open-air setting
Airborne environmental DNA (eDNA) is a promising tool for detecting a wide range of terrestrial taxa, including threatened and invasive species, from trace genetic material shed into the air. Yet, application of this technique in species management is constrained by a limited understanding of airborne eDNA ecology, including temporal persistence of signals in open-air environments. We investigated the temporal persistence of airborne eDNA in a natural outdoor setting, using the invasive Bennetts wallaby Notamacropus rufogriseus as a case study. We captured airborne eDNA from a single Bennetts wallaby carcass, deployed in an area where wallabies are otherwise not present. A total of 180 samples were collected, spanning the period before deploying the carcass, the 11 days it was on site, and for 32 days after its removal, at distances of 1, 10, and 100 metres using both active (fan-assisted) and passive (no fan) collection methods. Although overall detection rates were low, wallaby DNA was detectable up to 100 metres away shortly after the wallaby was introduced to the site and for up to three days after its removal. These findings indicate that airborne eDNA persists only briefly. Actively sampling air using battery-powered fans significantly improved detection rates relative to passive sampling. We demonstrate that airborne eDNA can detect individual organisms in outdoor environments, but reliable detection requires robust sampling and replication to capture rare, transient signals. By revealing how these signals persist over time, our findings provide a framework for optimizing field deployment and for distinguishing remnant DNA from new incursions.