Analysis of the genetic structure of Orostachys spinosa (L.) C.A. Mey (Crassulaceae) populations based on comparisons of cpDNA intergenic spacers trnH-psbA, trnQ-rps16 and rpl32-trnL

1 Institute of Biology and Soil Science FEB RAS, Vladivostok, Russia
2 Botanical Garden-Institute FEB RAS, Vladivostok, Russia

We studied the genetic structure of 9 populations of Orostachys spinosa - one of the most widespread species of Crassulaceae in Eurasia and 1 population of closely related O. japonica (Maxim.) A. Berger. The trnH-psbA, trnQ-rps16 and rpl32-trnL regions of cpDNA were successfully sequenced from 77 plants. The total length of concatenated sequence of the three regions was 2135 bp (including indels) for each plant (about 1.5% of the plastid genome). We found 55 (2.6%) variable sites, of which 48 were parsimony informative. Analysis of 77 sequences revealed 34 haplotypes. Of these 19 (55%) haplotypes were private (found in a single individual). The resulting network of haplotypes consisted of five putative haplogroups, combining population and samples from the same region (Bashkortostan, Chita, Magadan, Khabarovsky and Primorsky krai). We found a significant genetic differentiation between populations that corresponded with their geographical distribution and genealogical relationships. A large number of haplotypes per population (5-7), relatively high values of nucleotide and haplotype diversity (h > 0,85 and p > 0,003, respectively) characterize the populations from the eastern part of the species distribution range (Chita and Primorye territory). Perhaps this indicates that these populations are much older in comparison with those from the western part of the range. We can reason that the species spread in the southern Urals relatively recently. AMOVA revealed high differentiation of the chloroplast genome among the populations of O. spinosa (FST = 0.84545, p < 0.0001); i.e., the between-population component accounted for more than 86% of the total variance. These data pointed to the extremely low level of gene exchange between the populations and their significant subdivision. It should be noted that the genetic differentiation within and between populations of O. spinosa is comparable with the differentiation between this species and O. japonica.

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