In recent years, human activity directly and indirectly influenced the demography of moose in Poland. The species was close to extinction, and only a few isolated populations survived after the Second World War; then, unprecedented demographic and spatial expansions had occurred, possibly generating a very complex pattern of population genetic structure at the present-day margins of the species range in Poland. Over 370 moose from seven populations were collected from Poland, and partial sequences of the mitochondrial control region (mtDNA-cr; 607 bp) were obtained. In addition, the entire mtDNA cytochrome b gene (1,140 bp) and Y-chromosome markers (1,982 bp in total) were studied in a chosen set of individuals. Twelve mtDNA haplotypes that all belonged to the European moose phylogroup were recorded. They could be divided into two distinct clades: Central Europe and the Ural Mountains. The first clade consists of three distinct groups/branches: Biebrza, Polesie, and Fennoscandia. The Biebrza group has experienced spatial and demographic expansion in the recent past. Average genetic differentiation among moose populations in Poland at mtDNA-cr was great and significant (ΦST = 0.407, p < 0.001). Using mtDNA-cr data, four separate groups of population were recognized using spatial analysis of molecular variance and principal coordinate analysis, including a relict population in Biebrza National Park, a reintroduced Kampinos National Park population, as well as populations that were descendants of moose that colonized Poland from the east (Lithuania, Belarus, and Ukraine) and the north (former East Prussia). Among all the sequenced Y-chromosome markers, polymorphisms were found in the DBY14 marker in three populations only; four haplotypes were recorded in total. No significant differentiation was detected for this Y-linked marker among moose populations in Poland. Our mtDNA study revealed that a variety of different factors—bottleneck, the presence of relict, autochthonous populations, translocations, limited female dispersal, and the colonization from the east and north—are responsible for the observed complex pattern of population genetic structure after demographic and spatial expansion of moose in Poland.

We assessed migration rates and gene flow amongst 16 local demes and six larger groups of moose identified by a previous microsatellite study across the entire European range of the species. The most important barrier to gene flow, the Baltic Sea along with the mountainous region in northern Fennoscandia, separates two genetically distinct moose subpopulations-the Scandinavian and the continental subpopulations-that originate from different glacial refugia. Our results showed that moose effectively migrated over long distances, but statistically significant gene flow was shorter in the Scandinavian (300-400 km) compared to the continental subpopulation (400-500 km). The admixture rates in local demes were markedly lower in the Scandinavian, than in the continental part of the moose range. Weaker gene flow amongst local demes in Scandinavia resulted from the major barrier of the Scandinavian Mountains. In the generally panmixed continental subpopulation of moose, two demes-one in NE Poland and another in the Kirov Oblast, Russia showed slightly hampered gene exchange with neighbouring demes, whereas one deme, in Arkhangelsk region, NE part of European Russia, appeared to have very high gene flow into other demes. Different evolutionary and demographic histories, population densities and land topography (large rivers) could have contributed to the low level barriers to gene flow in the continental subpopulation of moose.