The use of environmental DNA as an early warning tool in the detection of new freshwater invasive non-native species

Successful removal and eradication of invasive non-native species (INNS) relies on early detection, ideally with pathway screening, to prevent any spread or outbreak in to a new region. The collection of DNA from environmental samples, known as environmental DNA or eDNA, is a revolutionary technique allowing the screening of target species without their prior collection or observation. This technique has been referred to as a 'game changer' for biodiversity monitoring, and the potential for INNS detection is particularly appealing. Current freshwater monitoring methods are heavily dependent on specimens being in sufficient number to be collected, thus making early detection at the beginning of an invasion, when numbers are likely to be low, challenging. However, the DNA of new INNS may still be prevalent in the environment, even at low densities, making detection possible. Here we review the recent developments in the application of eDNA for the detection of INNS, and assess the promise and pitfalls for its more widespread application.