Abstract: We represent a comparative analysis of GBSS1 gene fragment sequences for a number of species related to Elymus caninus: E. prokudinii, E. viridiglumis, E. goloskokovii, as well as a number of morphologically deviating biotypes, inhabiting Russia and Kazakhstan. Microevolutionary relationships between species were assessed from dendrograms derived from sequences of exons and introns. In all taxa St subgenome was represented by St₂ variants, rather typical of the North American ancestral line of Pseudoroegneria spicata than of the Asian line descending from P. strigosa. All putative relatives of E. caninus had H₁ subgenome variants linked around the Asian diploid carrier of the H genome from Hordeum jubatum, and were divided into two subclades. One of them (H_1-1) contained most of closely related to E. caninus clones, including E. uralensis. Another subclade (H_1-2) consisted of five variants phylogenetically related to E. mutabilis. We have also studied reproductive relationships between species E. goloskokovii, E. prokudinii, and E. viridiglumis and a degree of their integration into the E. caninus complex. Biotypes included in sexual hybridization formed a single recombination gene pool, within which slight differences in reproductive compatibility were observed. A comprehensive study of microevolutionary differentiation of taxa showed the expediency of taxonomic revision. The species mentioned should probably be relegated to infraspecific rank within Elymus caninus s. l.

Key words: Elymus, hybridization, microevolution, molecular markers, Poaceae, speciation, taxonomy