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The gene pool of populations of pedunculate oak (Quercus robur L.) from the north of the Russian part of the range of the species was studied using a set of 94 SNP loci. They were developed using the new generation DNA sequencing technology (ddRAD). Similar levels of genetic diversity were found in isolated stands with a small number of trees (expected heterozygosity HE = 0.313 ± 0.011, observed heterozygosity HO = 0.334 ± 0.004, allelic diversity υa = 1.540 ± 0.021, coefficient of inbreeding FIS = –0.067) and in relatively large populations (HE = 0.306 ± 0.010, HO = 0.318 ± 0.012, υa = 1.530 ± 0.021, FIS = –0.039). Statistically significant levels of interpopulation differentiation and population fixation (delta_T = 0.0993; Gregorius genetic distances d0 = 0.104–0.144, FST = 0.0725) were detected. Bayesian cluster analysis allowed identifying genetically distinct genetic groups. The results obtained are discussed taking into account the history of the distribution of pedunculate oak in the north of its range.

The aim of this study is to determine the genetic variability and differentiation among populations of pedunculate oak (Quercus robur) at the eastern margin of the species distribution range. We applied new set of 95 geographically informative nuclear SNP (single nucleotide polymorphism) loci developed using Double Digest Restriction Site Associated DNA (ddRAD), a new generation DNA sequencing technology. The study area is located in the basins of the Volga River and its two main tributaries, Kama and Belaya. Despite the strong reduction and fragmentation of pedunculate oak forests over the last several centuries and comparatively small sizes of present stands, a relatively similar genetic diversity of seven populations was observed (on average, allelic diversity υа = 1.472–1.603, observed heterozygosity HO = 0.305–0.358, expected heterozygosity HE = 0.272–0.343). The genetic distances between populations vary between 0.102 and 0.170 (on average, d0 = 0.128). We have identified the absence of a spatial genetic structure and the existence of genetically peculiar populations in the territory studied. The genetic distances of Gregorius between populations vary between 0.102 and 0.170 (on average, d0 = 0.128). Genetic differentiation among populations was statistically significant with a mean of the fixation index FST of 0.075. Populations from the Privolzhye Upplands and from northern parts of the study area make the most contribution to overall inter-population differentiation (d0 = 0.137). No significant differences exist among the samples at lowlands along the Volga river (d0 = 0.110). It was concluded that the multiplicity and different ages of local populations and the complexity of migration routes of the pedunculate oak from Pleistocene refugia and secondary Holocene shelters can cause this phenomenon.

We tested 95 new, geographically informative nuclear SNP loci of pedunculate oak in order to identify genetic differences of populations in the same seed zone. In a cluster analysis all individuals of the two studied stands are divided into two distinct groups. We observed statistically significant genetic differentiation of two populations (genetic distance d_0 = 0.170, parameter of differentiation 〖delta〗_T = 0.1696, genetic fixation F_ST = 0.0687) and higher genetic variability in the lowland stand (P = 91,58%, observed heterozygosity H_O = 0.364, expected heterozygosity H_E = 0.330, diversity of alleles υа = 1.58) in comparison to the oak stand in the Volga uplands (P = 77,89%, H_O = 0.327, H_E = 0.272, υа = 1.47). We concluded that these oak forests should be subdivided into different seed zones. Continuing the research by using the set of SNP loci and expanding the set of studied populations will supply Russian forestry by genetic information to optimize the forest seed zoning of the pedunculate oak.

The level of genetic diversity of populations of pedunculate oak (Quercus robur L.) of the southern part of the forest-steppe zone of Russia was studied using 79 SNP loci, developed on the base of the new genera-tion DNA sequencing technology ddRAD. Despite the significant decrease of the area of oak forests in the agricultural period, populations from the Lipetsk, Orel and Penza regions maintain a comparatively high and relatively similar levels of genetic diversity (observed heterozygosity HO = 0.319–0.344, ex-pected heterozygosity HE = 0.317–0.342, allelic diversity υа = 1.537–1.561). The observed distribution of genotypes corresponds to the frequencies expected by the Hardy-Weinberg equilibrium, the inbreeding coefficient varies from F = ‒ 0.019 to = F = + 0.011. The genetic distance of Gregorius between the sam-ples Orel and Penza (d0 = 0.138), which are geographically the most distant from each other, were statisti-cally significant. The results obtained are discussed in regard to the dynamics of oak forests in the histori-cal past and to problems of conservation and rational use of the gene pool of local populations.