Origin Area And Migration Route:Chloroplast DNA (?) In The Arctic-alpine Plant Koenigia Islandica (Polygonaceae)

Koenigia islandica is a nomorl arctic-alpine plant. Its geographical range is that from Himalaya and the high mountains in W China the species extends to form a slightly discontinuous Arctic circumpolar distribution with outliers in Scotland, in the Rocky Mountains of North America, and in southern South America. To infer historical processes(vicariance and/or dispersal), detect gene flow among populations, and clarify the origin area, glacial refuges and migration route of K. islandica, we studied on the population genetics and phylogeography of K. islandica using two non-coding region fragment of cpDNA. The main results are summarized as follows:We amplified and sequenced these two fragments for220individuals from26populations. A total of25haplotypes were identified based on58variations (40nucleotide mutations and18indels) between the cpDNA sequences. At the species level, haplotype and nucleotide diversities were0.834and0.00296, respectively. They were higher than other alpine plant which were distributed on the Tibet Plateau.The AMOVA showed that a larger proportion of the variation was distributed among populations(91.31%) than within populations (8.69%), The differences of among populations is significant level(FSx=0.9131, P<0.001). A test for phylogeographic structure of haplotype variation across the distribution of the species showed that NST(0.893±0.0464) was significantly higher than GST(0.736±0.0694)(U=2.57, P<0.01), indicating the distinct correlation between distribution and fixture of haplotypes.Molecular phylogenetic trees of25haplotypes were constructed with methods of maximum likelihood, maximum parsimony and bayesian inference, used K. pilosa as outgroup. Haplotypes from the same or adjacent regions were grouped into clades, representing three main lineages, designated the arctic clade, Sino-Himalayan clade, and H-D Mountain clade. These analysis, inferred from genetic diversity, the distribution of25haplotypes and nested clade analysis, together with geographical distribution pattern of the genus Koenigia and its pollen types, revealed that the H-D Mountains was considered as the origin area of the K. islandica. And the isolated distribution of haplotypes also suggested that the H-D Mountains and Dangla Mountains should be important glacial refugiums for K. islandica on the Tibet Plateau.These data, together with the arctic-alpine geographical distribution pattern of K. islandica, suggested that the migration route for the arctic-alpine plant K. islandica must have been from the H-D Mountains in W China extending northward to the Arctic circumpolar, first westward along the Himalayan, then northward across the Altay Mountains and the Central Siberian Plateau, firstly reached Taymyr Peninsula and then respectively around the Arctic migration in both directions which east and west, finally formed Arctic distribution by converging in northern Greenland gradually in different periods.By molecular Phylogenetics and BEAST, it was deduced that K. islandica population in north Finland migrated from the origin area after the H1and H2formation, and migration time was0.89Ma (in late Pleistocene).