Molecular Phylogeny Of Inner Mongolia Oxytropis DC. Based On 5.8SrDNA/ITS Sequence

Oxytropis DC. is widely distributed in grassland of Inner Mongolia. It is a kind of Legume resource with feeding, medicinal, ecological and ornamental values. Oxytropis species therefore produced marked effects on protecting the balance of prairie ecosystem, sustainable development and biodiversity. But the classification of partial species at subgenera and section level remains unclear. In this research, phylogenetic relationships of 32 sample sites of 12 Oxytropis species in Inner Mongolia were analyzed by comparing their internal transcribed spacers (ITS) and 5.8S gene of nuclear ribosomal DNA sequences. Phylogenetic trees were constructed by Maximum Likelihood and Neighbor Joining methods with MEGA 5.0 software. In addition, phylogeny trees based on ITS1 and ITS2 sequences were constructed by ML method. Results were conducted as follows:1. The branch type of phylogeny trees constructed by ML and NJ methods showed basically similar with each other, which conformed that when large number sequences with low divergences were used to constructed phylogeny tree, the topological structures always similar or same.2. The molecular data supported that Oxytropis was monophyletic taxa.3. The results were congruence with the point that put Oxytropis ciliata and O.inschanica into Subgenus Euoxytropis Section Xerobia in Flora of Intromongolica.4. The molecular data also supported the defination that put O.grandiflora into Section Orobia raised by domestic scholar.5. The results were congruence with the view that put O.ochrantha, O.verticillaris, O.bicolor and O.racemosa into Section Baicalia in Flora of Intromongolica. The C-T transition may be the main reason for the mixture of populations of O.verticillaris and O.racemosa.6. The phylogeny tree showed that O.squammulosa and O.aciphylla were formed a clade, rather than clustered in different subgenera described by some Floras. In conjunction with studies of floristic geography, it was suggested that O.aciphylla and O.squammulosa were geographical substitute species; the phylogeny tree showed that different populations of O.aciphylla were clustered in three clades. Therefore, the classification of O.aciphylla on subgenera level needs further research. It was presumed that the relationship among different geographic populations within species may influenced by vegetation types and habitats and O.aciphylla was presumed a polyphyletic taxon.7. O.glabra var.tenuis had a close relationship with O.glabra, which supported the opinion of treating O.glabra var.tenuis as a variant of O.glabra.8. O.filiformis and O.coerulea were sister species to that of Subgenus Euoxytropis, instead of clustering with species of Subgenus Phacoxytropis. Therefore, we supposed that O.filiformis and O.coerulea had close relationships with Subgen.Euoxytropis species.9. The phylogeny tree showed that populations may have marked effect on identifying species at low taxonomic levels.