Molecular Phylogenetic Analysis of the Endemic Far Eastern Closely Related Oxytropis Species of Section Orobia (Fabaceae)

The questions about the taxonomic status and phylogenetic relationships of the Far Eastern closely related species Oxytropis ochotensis, O. litoralis, O. erecta, O. ruthenica, and O. kunashiriensis of the section Orobia of the genus Oxytropis still remain unresolved. The study of the polymorphism of nucleotide sequences of the psbA–trnH, trnL–trnF, and trnS–trnG cpDNA intergenic spacers showed that populations of O. ochotensis and O. erecta are characterized by a low (0.378–0.495) haplotype (h) and a low (0.0006–0.0009) nucleotide (π) diversity, and in populations of O. ruthenica, h varies from 0.154 to 0.872 and π varies from 0.0002 to 0.0016. One O. ochotensis population from Magadan oblast and one O. ruthenica population from Russky Island (Primorsky krai) are monomorphic. Low nucleotide divergence of cpDNA between species O. ochotensis, O. erecta, and O. litoralis and also statistically insignificant genetic differentiation between them, the formation of a single haplogroup in the phylogenetic network, and the absence of species-specific molecular markers indicate the unity of their gene pool. A study of the ITS rDNA polymorphism revealed private ribotypes in O. ruthenica and O. kunashiriensis, the presence of a common ribotype in O. ochotensis, O. erecta, and O. litoralis, and the intraspecific polymorphism in O. ochotensis and O. erecta. The differences revealed in the chloroplast and nuclear genomes confirm the independence of O. ruthenica and O. kunashiriensis and suggest that O. erecta and O. litoralis are local phenotypes of the widespread polyploid species O. ochotensis. An analysis of the phylogenetic relationships of the cpDNA haplotypes showed a clear separation of O. ruthenica populations into two evolutionary lineages, but with a single ITS ribotype.