Phylogenetic Relationship of Subgenus Tsutsusi (Rhododendron) Based on ITS Sequences

The sequences of nrDNA internal transcribed spacers (ITS)(including 5 8S rDNA) of 12 species representing 2 sections of Subg Tsutsusi and 4 species representing 3 sections of Subg Pentanthera of Rhododendron ,were analyzed to reconstruct the phylogeny of Subg Tsutsusi and Subg Pentanthera using parasimony methods and R redowskianum Maxim of subg Therorhodion as outgroup.The size of ITS region within the three subgenera ranges from 642 to 645bp.The aligned length is 653 positions, which provide 6 58% variable sites and 3 68% phylogenetical informative sites when gaps are treated as missing.15 most parsimonious trees,with a length of 75 steps,consistency index ( CI ) of 0 9333 and retention index ( RI ) of 0 9515,were obtained.The topology of the strict consensus tree shows that: 1)Subg Tsutsusi is a monophyletic group, the bootstrap value is 81%; 2) R tashiroi is neither a member of Sect Tsusiopsis nor that of Sect Tsutsusi , R tashiroi should be a member of Sect Brachycalyx ; 3) R tsusiophyllum is a member of Sect Tsutsusi ; 4)the phylogenetic position of R schlippenbachii is not resolved in this study and needs further research.