Pine forests dominated by the Scotch pine in Eurasia are one of the largest units of the biosphere. The man-caused stress progressively aggravates the threat of an irreversible damage to their balanced natural genofund, which is a guarantee of the stability of forests in the future. Therefore one of the principal problems facing the modern forestry consists in the study of the genetic polymorphism and the chorogenetic differentiation of populations of this species within its vast natural habitat.

In the last 15 years we performed a wide-scale ecogenetic study of natural populations of Pinus sylvestris L. A unique gradient genogeographical approach and commonly accepted allozymic methods were used to analyze tissues of trees from 240 population samplings (30-48 trees each, 17 loci, 11 enzymatic systems) in a network of 5 latitudinal transcontinental and 14 meridional transects crossing the whole natural habitat of this species in plain and different-altitude mountain forests. The ecogeographical study of the reproductive isolation, the structure, the polymorphism, the differentiation, gradients and boundaries of populations was performed at four biochorological levels: adjacent local populations, their geographical groups, races and subspecies.

Parameters of the pollen distribution, anemochory and hydrochory of Scotch pine seeds were studied comprehensively. It was shown that the reproductive isolation of Scotch pine populations is determined mostly by pollen flows, while the dispersal rate depends on the hydrochory of seeds by river streams. An almost complete phenological isolation (85–100%), which was due to a different soil temperature in spring, and a genetic boundary between adjacent pine populations in dry lands and high bogs were found. Reliable phenotypic differences between their descendants were established against an equal ecological background in the pre-forest-steppe in Western Siberia and the East European Plain. A hypothesis of their genetic divergence in the Holocene has been comprehensively substantiated. The degree and the rate of divergence were three times smaller in the middle taiga than in the pre-forest steppe. Different-altitude cenopopulations (the Urals, the Caucasus, the Carpathians) were completely phenologically isolated if the vertical distance between their habitats was more than 400 m. They had a considerable genetic division in a disjunctive habitat (the Carpathians) and had not this division in a continuous habitat (the Northern Caucasus). Sharp gradients of the Nei genetic distances were detected for the insular pine populations in the steppe (Kazakhstan), adjacent basins of mountain rivers (the Carpathians), and those isolated by high mountain ridges (the Caucasus, the Carpathians, the Alps, the Pyrenees). It was found that the Crimean and Caucasian populations of Pinus kochiana Klotzsch ex C. Koch and P. armena C. Koch belong to Pinus sylvestris L. Validity of Mayr's hypothesis of homozygotation of marginal insular populations has been confirmed for the first time at the genetic level by the example of this species.

Generally, the genogeographical analysis demonstrated that the genetic differentiation between groups of populations in the landscape countries of the weakly disjunctive portion of the natural habitat of Pinus sylvestris in Northern Eurasia (Scandinavia, Central and Eastern Europe, the Urals, Western and Middle Siberia) is two-three times smaller than between these populations and marginal groups of insular populations in the southern and eastern parts of the natural habitat (the Mediterranean, the Trans-Caucasus, Central Kazakhstan, the Near-Amur region, Central Yakutia).

Note. Abstracts are published in author's edition