Spontaneous hybridization is widespread in the genus Populus and determines the nature of its evolution. To the present moment only three of the six known sections: Leucoides, Aigeiros, and Tacamahaca have retained the ability to crossbreed and form viable offspring. The purpose of this work is to study the facts of crossing species of different sections in the genus Populus, to consider the specifics of such hybrids in Russia. The identified hybrids between species of the Leucoides and Tacamahaca sections are not hybridogenic species, but single individuals close to first-generation hybrids. Hybridization between the Aigeiros and Tacamahaca species is observed in nature in the overlapping zone of their ranges. In North America, most hybrids are the result of crossing Populus deltoides (section Aigeiros) with various representatives of balsam poplars. In Asia, P. irtyschensis, a hybridogenic species that arose as a result of crossing P. laurifolia and P. nigra, is widespread. The analysis of the range of Populus irtyschensis showed that within the Altai-Sayan mountain country it is found in areas where the ranges of the parental taxa overlap; further south in Mongolia and the Xinjiang Uyghur Autonomous Region of China it is often found separately. In the Tom River basin, the factors contributing to the formation of the hybrid zone of P. laurifolia and P. nigra can be divided into two groups: those common to the genus and factors that have geographical specificity. Increased human economic activity in the Kuzbass contributes to a wider distribution of P. irtyschensis.

Keywords: hybridization of Populus, introgression of Populus, morphology of Populus, Populus, sections of Populus, variability of Populus