Nucleotide variation in an approximately 490 bp fragment of the mitochondrial DNA control region (mtDNA CR) was used to describe the genetic variation and phylogeographical pattern in the Eurasian beaver ( Castor fiber ) over its entire range. The sampling effort was focused on the relict populations that survived a drastic population bottleneck, caused by overhunting, at the end of the 19th century. A total of 152 individuals grouped into eight populations representing all currently recognized subspecies were studied. Sixteen haplotypes were detected, none of them shared among populations. Intrapopulation sequence variation was very low, most likely a result of the severe bottleneck. Extreme genetic structure could result from human-mediated extinction of intermediate populations, but it could also be an effect of prior substantial structuring of the beaver populations with watersheds of major Eurasian rivers acting as barriers to gene flow. Phylogenetic analysis revealed the presence of two mtDNA lineages: eastern (Poland, Lithuania, Russia and Mongolia) and western (Germany, Norway and France), the former comprising more divergent haplotypes. The low level of sequence divergence of the entire cytochrome b gene among six individuals representing six subspecies suggests differentiation during the last glacial period and existence of multiple glacial refugia. At least two evolutionary significant units (ESU) can be identified, the western and the eastern haplogroup. The individual relict populations should be regarded as management units, the eastern subspecies possibly also as ESUs. Guidelines for future translocations and reintroductions are proposed.

Many reintroduction projects for conservation fail, and there are a large number of factors that may contribute to failure. Genetic analysis can be used to help stack the odds of a reintroduction in favour of success, by conducting assessment of source populations to evaluate the possibility of inbreeding and outbreeding depression and by conducting postrelease monitoring. In this study, we use a panel of 306 SNP (single nucleotide polymorphism) markers and 487–489 base pairs of mitochondrial DNA control region sequence data to examine 321 individuals from possible source populations of the Eurasian beaver for a reintroduction to Scotland. We use this information to reassess the phylogenetic history of the Eurasian beavers, to examine the genetic legacy of past reintroductions on the Eurasian landmass and to assess the future power of the genetic markers to conduct ongoing monitoring via parentage analysis and individual identification. We demonstrate the capacity of medium density genetic data (hundreds of SNPs) to provide information suitable for applied conservation and discuss the difficulty of balancing the need for high genetic diversity against phylogenetic best fit when choosing source population(s) for reintroduction.

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with 8 figures and 6 tables Summary. Drainage ditches are the result of a large-scale anthropogenic transformation of the hydrographical network in the agrarian landscapes of European lowlands. These drainage ditches are readily occupied and transformed by beavers for their own needs, due to the paucity of remaining intact natural watercourses. The geomorphic consequences of beaver activities in inhabited streams are quite well documented in mountain environments of North America, especially for various aspects of sedimentation. There is, however, a lack of knowledge concerning other geomorphic effects resulting from beaver activities in the drainage ditches within agrarian lowlands. To assess these geomorphic effects, an investigation was conducted in the anthropogenically transformed landscape of the Middle Lithuanian Lowland to: (1) quantify the geomorphic effects, and (2) predict the shifts in the magnitude of total geomorphic effect as the size of beaver population changes. Two methods, aerial photographs and global positioning system, were used to map all ditches in selected sites and all available beaver-created visible structures therein. On the drainage ditch network scale, the quantitative geomorphic effect of beaver activities resulting from construction of dams, burrowing into the ditch slopes, and digging of lateral canals, as well as the development of scours where the beaver dams abut the drainage ditch slopes, was estimated to average about 35 m 3 km-1 of relocated substances. However, on the local scale, within one beaver-site, the total geomorphic effect was much greater, up to about 176 m 3. On the catchment scale of the whole hydrographical network, an increase in either the length of dammed drainage ditches by 10%, or the density of beaver-sites by 0.1 ps.km-2 , resulted in the potential growth of the total geomorphic effect by about 15 and 11 m 3 km-2 respectively. These quantities should be enhanced by about 6.5 times if the estimate of total geomorphic effect includes sedimentation in beaver ponds.

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