PHENOGENOGEOGRAPHY OF TREE POPULATIONS: PROBLEMS, METHODS AND RESULTS

Sannikov S.N., Petrova I.V.

Botanical Garden, Ural Division RAS, Russia, stanislav.sannikov@botgard.uran.ru

The study of the chorological structure, boundaries and structural gradients of natural populations is a fundamental, but still insufficiently explored, problem of the modern population biology of trees. Since 1967 we have been conducting a systematic study of regular features of the reproductive isolation, the chorological structure and differentiation of natural coniferous tree populations taking primarily common pines (Pinus sylvestris L.) as an example. The approaches of N.V. Timofeyev-Resovskii population-genetic school of thought as applied to dendrology are used.

Generalizing ideas formulated in the 20^th century, by the term "a population" of gamogenetic plants we imply a relatively isolated structurally and functionally integral and stable family of individuals of a single species having common specific origination, range, reproductive relations, genofund and microevolution tendencies, including all phenotypic parameters if the ecotope conditions are similar (Sannikov, 1993). Proceeding from this "working" definition, we developed and tested a system of principles and methods for analysis and evaluation of different (phenological, distance, mountain-mechanical, hydrochorous) forms of isolation and the integral reproductive isolation, as well as the degree of phenotypic and genetic differentiations of forest-forming coniferous species. In the recent decade RFBR financed a wide-scale research into the chorogenetic (over 200 isozymic assays) and phenotypic (77 samplings) structures, polymorphism and differentiation of plain and montane populations of the common pine, as well as almost throughout the range of this species.

A clearly pronounced and time-stable reproductive phenological isolation was established for adjacent populations of pines in dry lands and high bogs in the southern part of the forest zone and for cenopopulations growing at different altitudes in mountain regions of Northern Eurasia (the Urals, the Caucasus, the Carpathians, and the Trans-Baikal region) if their habitats are spaced more than 400 m in altitude. Regular features of the pollen propagation, the anemochory and the hydrochory of seeds of the common pine, the Siberian spruce and the Siberian larch were analyzed. It was found that the Nei genetic distance is reliably related to the integral reproductive isolation and the Machalanobis phenotypic distance. One of the most pronounced phenogenetic boundaries between natural populations in a continuous range – P. sylvestris populations in dry lands and high bogs – was detected and studied comprehensively for the first time. Sharp gradients were established between geographical groups of populations of this species isolated by ridges of the Pyrenees, the Alps, the Carpathians and the Caucasus, in insular pine forests in the Tobol region and the Aral-Turgai hollow, and adjacent basins of mountain rivers (the Carpathians).

The gradient analysis in the network of 5 latitudinal and 12 submeridional transects showed that the phenogenetic differentiation between groups of populations in the central part of the P. sylvestris range is two to three times smaller than between these groups and groups of insular populations on the southern and eastern edges of the range. A scale of genetic distances between intraspecific categories of the common pine was developed. It establishes their population-taxonomic classes. The structure of P. sylvestris L. is divided into 2 subspecies, 6 geographical races, and 9 geographical groups of populations. It was shown that Pinus kochiana Klotzsch ex Koch belongs to the system of the Pinus sylvestris L. species.

The formulated methodical principles, methods and regular features can serve as the basis for ecogenetic studies, taxonomic classification of tree populations, and development of adequate techniques for selective and forest-seed zoning and mapping on population-biological principles.

The study was supported by RFBR (project No. 05-04-48667) and RF HSS foundation (grant No. 9692.2006.4).