RESEARCH ARTICLE Microsatellite markers reveal clear geographic structuring among threatened noble crayfish (Astacus astacus) populations in Northern and Central Europe Riho Gross • Stefan Palm • Kuldar Ko ˜iv • Tore Prestegaard • Japo Jussila • Tiit Paaver • Juergen Geist • Harri Kokko • Anna Karjalainen • Lennart Edsman Received: 28 September 2012 / Accepted: 5 March 2013 / Published online: 14 March 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract Noble crayfish (Astacus astacus L.), the most highly valued freshwater crayfish in Europe, is threatened due to a long-term population decline caused mainly by the spread of crayfish plague. Reintroduction of the noble crayfish into restored waters is a common practice but the geographic and genetic origin of stocking material has rarely been considered, partially because previous genetic studies have been hampered by lack of nuclear gene markers with known inheritance. This study represents the first large scale population genetic survey of the noble crayfish (633 adults from 18 locations) based on 10 newly developed microsatellite markers. We focused primarily on the Baltic Sea area (Estonia, Finland and Sweden) where the largest proportion of the remaining populations exists. To allow comparisons, samples from the Black Sea catchment (the Danube drainage) were also included. Two highly differentiated population groups were identified corresponding to the Baltic Sea and the Black Sea catchments, respectively. The Baltic Sea catchment popu- lations had significantly lower genetic variation and private allele numbers than the Black Sea catchment populations. Within the Baltic Sea area, a clear genetic structure was revealed with population samples corresponding well to their geographic origin, suggesting little impact of long- distance translocations. The clear genetic structure strongly suggests that the choice of stocking material for re-intro- ductions and supplemental releases needs to be based on empirical genetic knowledge. Keywords Genetic variation Á Genetic differentiation Á Population structure Á Microsatellite DNA Á Conservation genetics Introduction Freshwater biodiversity is globally declining with inverte- brate species such as mussels (Geist 2011) and crayfishes (Reynolds and Souty-Grosset 2012) being particularly affected. This loss of biodiversity comprises multiple levels of biological organization, from habitat diversity to com- munities and species, to the level of intra-specific genetic diversity. Genetic variation is essential for securing the evolutionary potential of a species and its preservation is a prerequisite for effective conservation and sustainable harvesting (e.g. Allendorf et al. 2008). For threatened and simultaneously exploited species, knowledge of intra-spe- cies genetic diversity is particularly important. In such cases identification of genetic structuring may yield important information on existence of unique or vulnerable subpopulations, which can simultaneously be utilized when planning management actions like re-establishment or enhancement programs. R. Gross (&) Á K. Ko ˜iv Á T. Paaver Department of Aquaculture, Institute of Veterinary Medicine and Animal Sciences, Estonian University of Life Sciences, Kreutzwaldi 48, 51014 Tartu, Estonia e-mail: riho.gross@emu.ee S. Palm Á T. Prestegaard Á L. Edsman Department of Aquatic Resources, Institute of Freshwater Research, Swedish University of Agricultural Sciences, Sta ˚ngholmsva ¨gen 2, 17893 Drottningholm, Sweden J. Jussila Á H. Kokko Á A. Karjalainen Department of Biology, University of Eastern Finland, P.O. Box 1627, 70211 Kuopio, Finland J. Geist Aquatic Systems Biology Unit, Department of Ecology and Ecosystem Management, Technische Universita ¨t Mu ¨nchen, Mu ¨hlenweg 22, 85354 Freising, Germany 123 Conserv Genet (2013) 14:809–821 DOI 10.1007/s10592-013-0476-9