Low Variation and High Differentiation of Marginal Relict Populations of Pinus brutia Ten. in the Crimean–Caucasian Region

Genetic diversity in marginal populations of woody plants has been studied using the example of Calabrian pine Pinus brutia Ten. in the eastern Black Sea Region, i.e., at the northeastern limit of the species range. The variability of the microsatellite loci of chloroplast DNA (cpSSR) has been analyzed in six relict populations from the Crimea and the Caucasus, followed by their comparison with a P. brutia sample from the central part of the range (Turkey) and with other pine species growing in this region, Scots pine P. sylvestris L. and European black pine P. nigra Arn. (in three populations each). The average level of intrapopulation polymorphism ( H = 0.3657) has proved to be significantly lower in the Crimean–Caucasian populations of P. brutia than in the population sample from the main part of their range in Turkey ( H = 0.8857) and the Black Sea populations of P. sylvestris and P. nigra (average H = 0.9580 and 0.9574, respectively). A high level of genetic differentiation of P. brutia populations in the Black Sea Region has been revealed ( R ST = 9.81%). The clustering of populations by cpSSR markers is not related to their geographic location, and the Crimean populations do not differ from the Caucasian ones at the taxonomic level. It is likely that the subdivision of P. brutia populations by the haplotype composition and the differences in the level of intrapopulation variability (with H ranging from 0 to 0.6090) are due to the small size and isolation of northern Calabrian pine populations. For the first time, significant differentiation has been revealed between two unique habitats of P. brutia in the Crimea, which is expressed in the specific composition of cpSSR haplotypes. The observed differences at the four cpSSR loci between the three studied pine species are suitable for species identification.