Detection of three amphibian species in two city forests in Kristiansand,southern Norway, using environmental DNA analysis

In the context of global amphibian declines, there is need to map local amphibian populations to establish baseline knowledge of potential future species losses. Even in well-studied lakes and ponds within popular recreational areas near urban centres, information on amphibian occurrence can be limited. In this study, the local distributions of Lissotriton vulgaris, Rana temporaria and Bufo bufo  were assessed using eDNA analysis in two city forest areas of Kristiansand, Southern Norway. In the forest Baneheia, all three species  were detected, although R. temporaria was present in only half of the lakes. In the forest Jegersberg, L. vulgaris was detected in nearly all lakes while B. bufo only in fewer than half, and R. temporaria was not detected. Our results support the public observations system Artsobservasjoner.no that R. temporaria is uncommon in the coastal area of Kristiansand. Comparison of active netting with eDNA  analysis indicated that eDNA is a more reliable method for detecting amphibians. Interestingly, larvae of L. vulgaris were observed in one of the lakes in Baneheia inhabited by Salmo trutta, in a shallow bay with dense aquatic vegetation, demonstrating that newts can  successfully reproduce alongside trout under certain conditions.