Polymorphism of Birches in the Southern Trans-Urals

Tzvelev and Kulikov, who are leading monographers of the genus Betula, recognize the independence of birch microspecies. In the Southern Trans-Urals, B. krylovii belongs to this group. Most studies of Betula representatives have employed conventional phenotype-based methods and lack mechanisms to resolve taxonomic challenges in the complex genus. The study aimed to comprehensively asses the genetic and morphological polymorphism in birch populations along the Tobol River in the Southern Trans-Urals. Ploidy levels of Betula representatives, variability of chloroplast DNA fragments, and the morphological structure of leaf blades were examined in 10 birch sampling sites. Moderate genetic polymorphism and low interpopulation differentiation were observed in B. pendula of the Southern Trans-Urals. A low occurrence of B. pubescens was inferred from the ploidy data. According to the results of the comprehensive analysis, the taxa B. pendula and B. krylovii have similar phenotypic features, common chlorotypes, and the same ploidy level (2n), indicating that the taxonomic status of B. krylovii requires revision.