An evidence review for great crested newt eDNA monitoring protocols.
DNA based applications have the potential to significantly change how we monitor and assess biodiversity. Triturus cristatus, the great crested newt (GCN), is an example of a fairly cryptic pond species with a relatively low detection rate using traditional methods of sampling, which are resource intensive. A project was carried out in 2013-2014 to establish the performance of environmental DNA techniques for determination of the presence of GCN in a wide variety of pond habitats across the United Kingdom. As part of this project, a technical advice note was developed which contained the eDNA field and laboratory methods to be used for the detection of GCN using eDNA for use from the 2014 GCN season onwards. This paper reviews the results of 9 years of GCN eDNA surveillance by Natural England to (1) compare the effectiveness of the ethanol precipitation and filtration eDNA capture methods for GCN; (2) evaluate the field protocol for collecting and processing the water samples, including the use of single-use plastics, how this can be minimized, use by dates for kits subject to appropriate storage regime and recommend any changes to the current field protocols supported by relevant evidence; (3) evaluate the laboratory procedures specified in the current protocol (WC1067) in light of developments since 2014 and recommend any changes to the current protocols supported by relevant evidence (including different potential changes to the same part of the protocol); (4) create a list of any projects underway looking at GCN protocols and/or methodologies; (5) consider areas of the current protocol where flexibility could be allowed rather than being fixed while still maintaining appropriate assurance in methods and results and (6) conduct a cost-benefit analysis of any proposed changes to the methodologies (field and laboratory) compared to the existing protocol.