Population genetic analysis of Fagus orientalis Lipsky from the territory of the Crimea and the Caucasus

The genetic structure of 20 populations of Fagus orientalis Lipsky (oriental beech) from the territory of the Crimea and the Caucasus was studied on the basis of microsatellite polymorphism (SSR – simple sequence repeats). The isolation distance test performed in the GenePop program showed a high correlation of genetic differences and the logarithm of geographic distance in geographic coordinates at the 0.91 level. Interpopulation genetic differentiation of Fagus orientalis (Fst) ranged from 0.01 to 0.67. On the basis of the obtained genetic data and analysis of the literature on fossil materials, we present a preliminary reconstruction of the possible pathways for spread and the formation of the modern area of the species in the Crimea and on the Caucasian Isthmus within the Caucasian ecoregion. The earliest separation occurred in the populations of the mountainous Crimea and the Stavropol Upland, which retained the unique features of the genotype of the ancestral form in conditions of island isolation. Apparently, beeches from relict mid-mountain populations in refugia of mesophilic vegetation are close to the ancestral form: Colchis (Avadhara, Abkhazia) in the west and Kakheti (Lagodekhi, Georgia) in the east. The observed similarity at the upper border of the beech belt in different regions of the Caucasian Isthmus indicates a parallelism in the development and formation of high-mountain populations of the species.