Using eDNA to detect freshwater invasive non-native species under controlled conditions.

Invasive Non-Native Species (INNS) are a principal threat to global biodiversity and the early detection of new introductions is key to facilitate a rapid response to limit the risk of establishment and spread. Related to this, there is growing interest in using environmental DNA (eDNA) for INNS detection. The applied use of eDNA in ecology is, however, in its relative infancy with few species for which regulator-approved methods are available. Here, laboratory trials were conducted to investigate the use of commercially available eDNA assays for detecting two high priority INNS in the UK, killer shrimp (Dikerogammarus villosus) and signal crayfish (Pacifastacus leniusculus), at different population densities. For killer shrimp, DNA of the expected fragment size was detected from all three trials where animals were maintained at a density of 1 per 1 L but species confirmation by Sanger sequencing was only possible for one of these replicates. Whilst capillary electrophoresis detected DNA of the expected fragment size in serially diluted samples down to a density of 1 shrimp in 100 L, this could not be confirmed by sequencing. Signal crayfish DNA was detected by qPCR in all four trials where animals were housed at a density of 1 per 10 L. Using serial dilutions, it was possible to detect signal crayfish in samples representing a density of 1 per 1,000 L, however this was unreliable. These results demonstrate the potential for using eDNA as a detection method for killer shrimp and signal crayfish but also highlights that detectability is species/assay specific and dependant on population density. The insights gained will help inform decisions surrounding the appropriateness of using these eDNA assays, and improve interpretation of any results generated. [ABSTRACT FROM AUTHOR]