Orostachys spinosa (Crassulaceae) origin and diversification: East Asia or South Siberian Mountains? Chloroplast DNA data

摘要

Limited data are available on genetic structures of the herbaceous plant species populations inhabiting mountainous areas of Siberia and Northeastern Asian (Russian Far East). Although this area was not directly impacted by the extensive ice-sheets during the Quaternary, it experienced significant climatic fluctuations that influenced rich local flora.Orostachys spinosa(Crassulaceae) lacks any adaptations for long-distance dispersal, yet the species is characterized by an unusually wide range spanning from the Urals to the coast of the Pacific Ocean. We studiedO. spinosaphylogeography and genetic diversity across its range sampling 203 individuals from 21 natural populations. Using sequences from three chloroplast DNA non-coding regions, we revealed 82 haplotypes and observed high level of population differentiation indicating presence of the phylogeographic structure (G(ST) = 0.501 andN(ST) = 0.822 (p < 0.01)). In concordance with the previous phylogenetic analyses based on ITS rDNA data, parsimony network revealed two distinct cpDNA haplotype lineages deferring in their structure and characteristics of genetic diversity. The split between these haplotype groups can be dated to the Pliocene (ca. 3.6 Mya). According to our estimates diversification in the Western group of populations took place ca. 1 Mya earlier than in the Eastern group (3.1 Mya and 2.26 Mya, respectively). Apart from the generally accepted notion about East Asian origin ofO. spinosa, our results indicated that the species could have originated in mountains of Southern Siberia (Altai). This region was colonized independently fromO. thyrsiflorawhich has a largely overlapping distribution in this area.