Local extinction and recolonization events can shape genetic structure of subdivided animal populations. The gray wolf (Canis lupus) was extirpated from most of Europe, but recently recolonized big part of its historical range. An exceptionally dynamic expansion of wolf population is observed in the western part of the Great European Plain. Nonetheless, genetic consequences of this process have not yet been fully understood. We aimed to assess genetic diversity of this recently established wolf population in Western Poland (WPL), determine its origin and provide novel data regarding the population genetic structure of the grey wolf in Central Europe. We utilized both spatially explicit and non-explicit Bayesian clustering approaches, as well as a model-independent, multivariate method DAPC, to infer genetic structure in large dataset (881 identified individuals) of wolf microsatellite genotypes. To put the patterns observed in studied population into a broader biogeographic context we also analyzed a mtDNA control region fragment widely used in previous studies. In comparison to a source population, we found slightly reduced allelic richness and heterozygosity in the newly recolonized areas west of the Vistula river. We discovered relatively strong west-east structuring in lowland wolves, probably reflecting founder-flush and allele surfing during range expansion, resulting in clear distinction of WPL, eastern lowland and Carpathian genetic groups. Interestingly, wolves from recently recolonized mountainous areas (Sudetes Mts, SW Poland) clustered together with lowland, but not Carpathian wolf populations. We also identified an area in Central Poland that seems to be a melting pot of western, lowland eastern and Carpathian wolves. We conclude that the process of dynamic recolonization of Central European lowlands lead to the formation of a new, genetically distinct wolf population. Together with the settlement and establishment of packs in mountains by lowland wolves and vice versa, it suggests that demographic dynamics and possibly anthropogenic barriers rather than ecological factors (e.g. natal habitat-biased dispersal patterns) shape the current wolf genetic structure in Central Europe.

APB BirdLife Belarus Engelsa 34A 1 220030 Minsk Belarus

Association for Nature Wolf Twardorzeczka Cynkowa 4 34 324 Lipowa Poland

Association for Nature Wolf Twardorzeczka Cynkowa 4 34 324 Lipowa Poland Institute of Romance Studies Faculty of Modern Languages and Literature Adam Mickiewicz University in Poznań Al Niepodległości 4 61 874 Poznań Poland

Department of Animal Science and Food Processing Faculty of Tropical AgriSciences Czech University of Life Sciences Prague Kamýcká 129 Prague 6 165 00 Czech Republic

Faculty of Science Charles University Prague Viničná 7 128 43 Prague Czech Republic Faculty of Science University of Ostrava Chittussiho 10 170 00 Ostrava Czech Republic

Faculty of Science University of Ostrava Chittussiho 10 170 00 Ostrava Czech Republic

Institute of Genetics and Biotechnology Faculty of Biology University of Warsaw Pawińskiego 5a 02 106 Warsaw Poland

Institute of Genetics and Biotechnology Faculty of Biology University of Warsaw Pawińskiego 5a 02 106 Warsaw Poland Association for Nature Wolf Twardorzeczka Cynkowa 4 34 324 Lipowa Poland

Institute of Genetics and Biotechnology Faculty of Biology University of Warsaw Pawińskiego 5a 02 106 Warsaw Poland Association for Nature Wolf Twardorzeczka Cynkowa 4 34 324 Lipowa Poland Department of Vertebrate Ecology and Zoology Faculty of Biology University of Gdańsk Wita Stwosza 59 80 308 Gdańsk Poland

Roztocze National Park Plażowa 2 22 470 Zwierzyniec Poland

State Nature Conservancy of Slovak Republic Tajovského 28B 974 01 Banská Bystrica Slovakia

Tatra National Park Kuźnice 1 34 500 Zakopane Poland

Vytautas Magnus University K Donelaičio 58 44248 Kaunas Lithuania

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