Divergence of Oxytropis Species from the Section Verticillares (Fabaceae) of Steppe Flora of Baikal Siberia Based on Analysis of Chloroplast DNA

The analysis of nucleotide sequence polymorphism of chloroplast DNA psbA–trnH, trnL–trnF, and trnS–trnG intergenic spacers in the Oxytropis lanata, O. myriophylla, O. oxyphylla, O. selengensis, and O. stukovii (section Verticillares) of the steppe flora of Baikal Siberia demonstrated that the populations are characterized by a high haplotype (0.634–1.000) and relatively low (0.0003–0.0045) nucleotide diversity. Statistically significant values of genetic distances between the populations of the same species change from 0.19382 to 0.43449. Marker nucleotide substitutions and indels were detected in O. lanata, O. gracillima, O. interposita, O. pumila, and O. mongolica, indicating a significant divergence of their chloroplast genomes. A weak differentiation (ΦST = 0.137, P < 0.0001) between O. oxyphylla, O. selengensis, O. stukovii and O. bargusinensis and also low values of genetic distances (0.08939–0.32339) (corresponding to interpopulation distances), absence of differentiating molecular markers, formation of a single haplogroup in the median network, and presence of common haplotypes indicate that these species are a genetically homogeneous group probably formed as a result of relatively recent and rapid divergence from the common ancestor, as well as a high degree of interspecies hybridization.