目的 构建碎米桠Isodon rubescens及其与近缘种之间系统发育关系，准确鉴别碎米桠及其近缘种。方法 提取碎米桠及其近缘种DNA，对核基因ITS片段和叶绿体基因psbA-trnH序列扩增和测序，计算物种种内、种间Kimura 2-parameter（K2P）遗传距离。采用最近距离、相似性搜索、构建Neighbor-joining（NJ）系统聚类树3种方法进行鉴定分析。结果 ITS和psbA-trnH分子系统树支持碎米桠5个居群样本聚为一单系分支，支持率为94%和68%；其中，碎米桠与毛叶香茶菜、香茶菜和内折香茶菜聚在一支，支持率为70%和51%；溪黄草和显脉香茶菜构成姐妹群分支，支持率为81%和63%。碎米桠及其近缘种种间ITS和psbA-trnH序列的K2P遗传距离为0.007 08～0.072 61和0.008 06～0.024 76，均远大于碎米桠种内的遗传距离0～0.001 76和0～0.002 68。结论 碎米桠与毛叶香茶菜、香茶菜和内折香茶菜亲缘关系较近，溪黄草和显脉香茶菜亲缘关系最近。ITS和psbA-trnH序列可以准确鉴别碎米桠及其近缘种。

Objective To construct the phylogenetic relationships of Isodon rubescens and its relative species, and accurately identify I. rubescens and its relative species. Methods Total genomic DNA was isolated from I. rubescens and its relative species. Nuclear DNA internally transcibed spacer (ITS) and chloroplast gene psbA-trnH sequences were amplified and sequenced. The Kimura 2-parameter (K2P) distances were calculated. Identification analyses were performed using Nearest Distance, BLAST1, and Neighbor-joining (NJ) methods. Results The NJ trees (ITS and psbA-trnH data) indicated that the five populations of I. rubescens formed a monophyletic clade [Bootstrap (BS) = 94% and 68%]. I. rubescens and I. japonicus, I. amethystoides, I. inflexus formed one monophyletic clade (BS = 70% and 51%), and I. serra was sister to I. nervosus (BS = 81% and 63%). The K2P genetic distances of ITS and psbA-trnH data between I. rubescens and its relative species were (0.007 08—0.072 61) and (0.008 06—0.024 76) which were far higher than intra-specific genetic distances of I. rubescens (0—0.001 76) and (0—0.002 68). Conclusion I. rubescens is closely relative to I. japonicus, I. amethystoides, and I. inflexus. The closest relative of I. serra is I. nervosus. ITS and psbA-trnH are two efficient barcodes for the identification of I. rubescens and its relative species.

国家自然科学基金面上项目（31070171，31270236）；科技部国家星火计划项目（2012GA750004）