基于ITS序列分析探讨杜鹃属映山红亚属的组间关系

以叶状苞亚属的叶状苞杜鹃为外类群，以杜鹃属映山红亚属（subg.Tsutsusi)2组12种杜鹃和羊踯躅亚属（subg.Pentanthera）3种4种杜鹃的ITS区（包括5.8S rDNA)的序列了系统学分析。3个亚属的ITS区序长度范围为642－645bp。排序后ITS区的序列长度为653个位点，gap做缺失处理时，变异位点和信息位点分别占6．58％和3．68％。运用PAUP4．0软件分析，获得15个最简树，步长为75，一致性指数（CI）和维持性指数（RI）值分别为0．9333和0．9515，利用15个最简约树获取严格一致树，结果表明：1）映山红亚属为一单系类群，其内部支持率为81％；2）不支持将R.ashiroi独立成假映山红组，也不支持将R.tashiroi并入映山红组，而支持将R.tashiroi并入轮生叶组中的观点；3）支持将R.tsusiophyllum并入映山红组中的观点；4）大字杜鹃的系统位置还需进一步的研究。

Phylogenetic Relationship of Subgenus Tsutsusi (Rhododend ron) 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.