ORIGIN, STRUCTURE AND DYNAMICS OF ПОПУЛЯЦИЙ POPULUS × JRTYSCHENSIS CH. Y. YANG POPULATIONS IN THE AREA OF NATURAL HYBRIDIZATION

P. × jrtyschensis is widely-spread natural hybrid in geographic ranges P. laurifolia Ledeb. and P. nigra L. in Altai-Sayany highlands. In the basin of Tom it is observed sporadically in mixed timber stands of parental generations. Sometimes, it makes populations of hybrid habitual area appeared due to natural and anthropogenic factors. The first ones appear in the bottomland as a result of catastrophes caused by river-bed evolution. In some years, snow and icy floods result in destruction of vegetative ground cover and therefore natural hybrid populations. Their origin is cyclic and relates to hydrological water regimes. Anthropogenic populations appear within and outside the bottomland due to human economic activity that results in destruction of vegetative ground cover. Population age that is defined by means of the number of rings on tree trunks, doesn’t allow to date poplar planting on the sediments situated near a river channel. It defines the time when its growth is getting from bushy to tree one. It also shows that in spite of annual poplar bearing, the conditions for successful mass colonization of the sediments situated near a river channel appear approximately once every 10 years in the basin of Tom. The age of hybrids in natural populations exceeds 30 years whereas their number is reducing. This reflects the effect of natural selection in natural conditions that results in elimination of hybrids as they cannot compete with parental varieties. Variation of morphometric parameters of P. × jrtyschensis leaves in natural conditions is not high in spite of dominance of intermediary forms as they are closer to one of the parents. In anthropogenic populations selection impact is low, variation is higher, forms are of different age and quality according to morphology of leaves. Therefore anthropogenic hybrid areas are significant for selecting valuable forms of spontaneous hybrids. In natural and anthropogenic populations, hybrids turn to the P. laurifoli side.

poplar, hybridization, hybrid populations, age structure, dynamics, morphometry, тополь, гибридизация, гибридные популяции, возрастная структура, динамика, морфометрия

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