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07 April 2014
Environmental DNA (eDNA) is a new method being trialled to survey for the presence or absence of great crested newts Triturus cristatus in water. Recently published results of a study, assisted by ECOSA staff and funded by Defra, validate this new more efficient approach.
An eDNA assessment requires the collection of pond water samples, typically at the same time that a Habitat Suitability Index (HSI) assessment of water bodies is conducted. This can be performed at any time of day, as opposed to the relatively labour-intensive, nocturnal method of torch counting and is therefore expected to reduce the costs surveying for great crested newt (GCN).
In the detailed methodological study from Defra, eDNA detected GCN with an accuracy of 99.3% (139 out of 140 ponds where GCN were present). When torch counting and bottle trapping were combined, as is normal practice in amphibian surveying, the traditional method was found to be only slightly less effective than eDNA. There were no false positives in the study, i.e. eDNA did not record newts where they were believed to be absent. The study found that newt abundance was weakly correlated with the eDNA 'score': sites with low eDNA scores always had low newt counts but sites with higher eDNA scores did not always have more newts (Biggs et al. 2014). Where GCN is found to be present, traditional methods will still be used to establish population size.
Overall, collecting eDNA appears to be a highly effective method for determining whether GCN are present or absent during the breeding season. However, the eDNA will degrade in the water after 20 days (Thomsen et al. 2012). It is not known yet how effective the method is outside this period and, at the moment, eDNA provides only limited information on newt abundance (Biggs et al. 2014).
References
Biggs J, Ewald N, Valentini A, Gaboriaud C, Griffiths RA, Foster J, Wilkinson J, Arnett A, Williams P and Dunn F (2014) Analytical and methodological development for improved surveillance of the Great Crested Newt. Defra Project WC1067. Freshwater Habitats Trust: Oxford.
Thomsen P, Kielgast J, Iversen LL, Wiuf C, Rasmussen M, Gilbert MTP, Orlando L and Willerslev E (2012). Monitoring endangered freshwater biodiversity using environmental DNA. Molecular Ecology, 21: pp. 2565-73
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