Mammalian Biology 79 (2014) 287–296 Contents lists available at ScienceDirect Mammalian Biology jou rn al hom epage: www.elsevier.com/locate/mambio Original Investigation Admixture of two phylogeographic lineages of the Eurasian beaver in Poland Aleksandra Biedrzycka a,∗ , Magdalena Konior b , Wiesław Babik b , Magdalena ´ Swisłocka c , Mirosław Ratkiewicz c a Institute of Nature Conservation, Polish Academy of Sciences, Al. Mickiewicza 33, 31-120 Kraków, Poland b Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland c Institute of Biology, University of Bialystok, Swierkowa 20B, 15-950 Bialystok, Poland a r t i c l e i n f o Article history: Received 19 November 2013 Accepted 25 April 2014 Handled by Paul Grobler Available online 5 May 2014 Keywords: Castor fiber Expansion Genetic admixture Phylogeographic lineages Reintroduction a b s t r a c t The Eurasian beaver (Castor fiber) represents an uncommon example of an endangered species in which the restoration programs proved a spectacular success and led to enormous spatial and demographic expansion. Documented reintroduction of beavers in Poland has been conducted using animals of the eastern European origin, most likely derived from the eastern mtDNA lineage. However demographic and spatial expansion of beavers from Germany, which represent the western lineage, may have led to admixture of these two genetically distinct entities in Poland. We detected significant genetic dif- ferentiation between the populations from W and NE Poland both in mitochondrial DNA control region and microsatellites, but also substantial admixture including apparent first-generation migrants between regions. Our results indicate that beavers from the western mtDNA lineage have contributed considerably to the Polish population, particularly in W Poland. As there have been no adequately documented translo- cations of beavers from the western European populations to Poland, the observed situation appears to result from natural migration or range expansion from the west. In contrast to previous findings we detected a substantial diversity in mtDNA control region, which indicates that either the variation in relict populations has been underestimated, or that additional relict beaver populations survived at the end of the 19th century in Poland and Germany as indicated by considerable similarity of ancient and extant mtDNA haplotypes. The implications of our findings for beaver conservation and management are discussed. © 2014 Deutsche Gesellschaft für Säugetierkunde. Published by Elsevier GmbH. All rights reserved. Introduction One of the consequences of range expansion may be a secondary contact between genetically differentiated populations. If these are not substantially reproductively isolated, admixed populations will form. Such zones of secondary contact have been described in many areas, and in temperate regions are often interpreted as a consequence of postglacial expansion of genetically differenti- ated populations from separate glacial refugia (Taberlet et al. 1998; Avise 2004; Hewitt 2004; Hofreiter and Stewart 2009; Shafer et al. 2010). Some of these contact zones may actually be hybrid zones formed between partially reproductively isolated incipient species, but many zones are relatively broad and thus unlikely to be main- tained by strong selection against hybrids (Avise 2004; Abbot et al. ∗ Corresponding author. Tel.: +48 12 370 35 51; fax: +48 12 632 24 32. E-mail address: biedrzycka@iop.krakow.pl (A. Biedrzycka). 2013). Paleophylogeographic data suggest that such zones of sec- ondary contact may by transient, because a thorough mixing of populations and the loss of phylogeographic structure over the expansion areas occurred in some species during the last inter- glacial (Hofreiter et al. 2004). Secondary contact and admixture between genetically differentiated populations may also occur dur- ing biological invasions (Kolbe et al. 2008; Keller and Taylor 2010). Genetic consequences of range expansions have recently received considerable attention (Currat et al. 2008; Excoffier et al. 2009; Petit and Excoffier 2009). The Eurasian beaver (Castor fiber) represents an uncommon example of a species in which the dynamics of recolonization and its genetic consequences may be traced almost in real time. Particu- larly interesting in this context is the situation in the regions where genetically differentiated populations representing distinct evolu- tionary significant units (ESU sensu Moritz (1994) and Durka et al. 2005) meet during expansion. The territory of present-day Poland is an area where such a contact zone may form and admixture follow. http://dx.doi.org/10.1016/j.mambio.2014.04.005 1616-5047/© 2014 Deutsche Gesellschaft für Säugetierkunde. Published by Elsevier GmbH. All rights reserved.