Phylogeny of the Aconitum delavayi complex (Ranunculaceae)based on evidence from nuclear ribosomal ITS sequences
紫乌头复合体nrDNA的ITS序列与系统发育分析

Internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA (nr DNA) were used to investigate the phylogeny of the Aconitum delavayi complex that was found mainly in Hengduan Mountains, SW China. Based on maximum parsimony and neighbor-joining analyses, we reconstructed the phylogenetic relationships of 27 taxa of Aconitum including 8 taxa of the A. delavayi complex. The two methods generated similar ITS trees, which showed that ser. Volubilia could not be a monophyletic group and that ser. Stylosa could hardly be distinguished from ser. Ambigua. Such results indicate that the present serial delimitation of the subgenus Aconitum made by Wang in Flora Reipublicae Popularis Sinicae is problematic. The close phylogenetic relationships among some species endemic to the Hengduan Mountains in NW Yunnan may be attributed to the recent speciation events of Aconitum species in this area. The Aconitum delavayi complex that mainly occurs in the Hengduan Mountains is separated into three clades in the ITS trees, implying that the complex is not a natural lineage in terms of genetic relationships. Of the three clades, the one including A. episcopale is quite distinct from the clade consisting of A. delavayi, A. tuguancunense, A. stapfianum and A. vilmorinianum, although they are all mainly distributed in NW Yunnan and there is a high degree of morphological similarity among them. Another clade includes A. campylorrhynchum and A. sungpanense from NW Sichuan, NE Chongqing and Shaanxi. Consequently, the A. delavayi complex is not a monophyletic group and may have originated from three different lineages.