Natural hybridization and taxonomy of birches in North Asia

Currently there is a complicated situation in the taxonomy of widespread species such as birch (Betula L.). A large number of species of this genus in Siberia and the Russian Far East has been described, but one encounters an insurmountable obstacle when trying to carry out a more detailed study: the impossibility of finding them for a second time in nature or at least collect plants that have identical characteristics to the typical examples of the described species. All of these species are characterized by a very high variability of traits. These are the traits of Betula pendula and B. microphylla in the southern parts of Central Siberia and Betula pendula (= B. platyphylla) and B. lanata in Eastern Siberia and in the northern regions of the Russian Far East. This suggests intense and widespread hybridization between these species. In connection with this, research of this genus throughout North Asia has begun. These studies have been carried out over 40 years. To date, many works in periodicals and several monographs have been published using the data of numerous expeditions. This paper shows the role of natural hybridization in plant taxonomy using the example of the Siberian species of birch. It is necessary to have a clear understanding of the hybridization processes on large areas that include the ranges of contact species. Solving problems of taxonomy only by studying small local populations is a hopeless pursuit.