A review of the influence of beaver Castor fiber on amphibian assemblages in the floodplains of European temperate streams and rivers

Abstract

A are a highly endangered vertebrate class in Europe (Temple & Cox, 2009) and all European species are protected by the European Union Habitats Directive 92/43/EEC. Small headwater, 1st to 3rd order streams account for 60–80 % of the streams of a catchment area (Benda et al., 2005; Spänhoff et al., 2012; Ulevičius et al., 2011), and their associated floodplains are considered to support naturally low amphibian species richness across large areas of northern and temperate Europe (Günther, 1996; Thiesmeier, 2004; Weddeling & Willigalla, 2011). In south-west Europe (west of the Pyrenees) and in the European Mediterranean regions, several amphibian species, including Salamandrina terdigitata, Chioglossa lusitanica, Rana graeca, R. italica and R. iberica occur in flowing waters (Nöllert & Nöllert, 1992), whilst their numbers are very limited in the rest of Europe. In the temperate regions east of the Pyrenees there is only one amphibian species, the fire salamander Salamandra salamandra, which tends to inhabit small headwater streams, breeding in fish-free streams but also in associated floodplain ponds (Thiesmeier & Günther, 1996). Additional species are more commonly found in adjacent floodplain ponds, inlcuding palmate and alpine newts Lissotriton helveticus and Ichthyosaura alpestris, the common frog Rana temporaria (Weddeling & Willigalla, 2011) and to a lesser extent the midwife toad Alytes obstetricans (Borgula & Zumbach, 2003). Outside of this area, there are no amphibian species in eastern and northern Europe that prefer to reproduce in flowing waters. Compared to floodplains of larger lowland and gravel-bed rivers, the floodplains of these headwater streams have fewer ponds, lower hydrodynamics and unfavourable thermal conditions due to associated closedcanopy riparian forests (Skelly & Freidenburg, 2000). A review of the influence of beaver Castor fiber on amphibian assemblages in the floodplains of European temperate streams and rivers