利用叶绿体DNA trnL-F序列初步探讨菊科风毛菊属的系统发育

风毛菊属Saussurea DC.是菊科物种分化十分剧烈和分类处理十分困难的一个属。该属的单系起源性质、属下分类系统以及一些独特形态物种的系统位置尚不清楚，有待进一步验证。本文测定了代表该属5个亚属37种植物43个样品和川木香属Dolomiaea DC.的１种样品的叶绿体DNA trnL-F序列，并调取菜蓟族Cardueae Cass.与风毛菊属具有一定亲缘关系的13属的该序列，一起进行了分支分析，重点验证该属的属下形态分类系统以及形态特殊、青藏高原地区特有的雪兔子亚属subgen. Eriocoryne

A preliminary investigation on the phylogeny of Saussurea (Asteraceae:Cardueae) based on chloroplast DNA trnL-F sequences

Saussurea DC., a highly diversified genus with about 400 species in the Asteraceae, has been an extremely difficult group in both taxonomical and phylogenetic studies. The monophyletic origin, infrageneric classification and systematic positions of some species with unique gross morphology remain unclear for this genus. The main aim of this study was to examine infrageneric relationships of Saussurea as inferred from molecular evidence against the existing supraspecific classification on the basis of the morphological characteristics. In addition, we intended to use phylogenetic analyses of DNA sequence data to investigate systematic position and relationship of each species in sect. Pseudoeriocoryne (subgen. Eriocoryne) and test the monophyly of this section, which is likely to be established based on the morphological characters with convergent evolution. We sequenced chloroplast DNA trnL-F for all four species of sect. Pseudoeriocoryne and other 33 species, which represent the recognized five subgenera in Saussurea, and conducted a phylogenetic analysis together with 14 related genera in the Cardueae Cass. The variation of trnL-F sequences is very low among the sampled species in spite of their extremely diverse morphology. Five subgenera in Saussurea delimitated based on morphological characters were unrecognized on all most parsimonious trees. Sect. Pseudoeriocoryne is a polyphyletic group, and the four species in this section were found to be distantly related to each another, and showed no close relationship with the other species in subgen. Eriocoryne. The morphological characters to circumscribe this section had separately evolved four times. An 18-bp insertion was identified for S. polycolea var. acutisquama in sect. Pseudoamphilaena of the subgen. Amphilaena and other four species, S. hieracioides, S. superba, S. tatsienensis and S. katochaete from the subgen. Saussurea. This long and unique insertion was only recognized for these five species in the total Cardueae, and it must have evolved before the morphological diversification of this species complex. However, this insertion was not found in S. polycolea and another population of S. katochaete. Therefore, the insertion found in S. polycolea var. acutisquama and S. katochaete might have resulted from haplotype introgression or retaining because of hybridization. This study demonstrates for the first time that species even within a genus had also undergone convergent evolution in their morphology under the same ecological selection pressure of the Qinghai-Tibet arid habitats. This implication is especially important for those researches, which study relationships of the species distributed there and name taxonomical entities based exclusively on the gross morphology. In addition, our preliminary results indicate that Saussurea provides a typical case for studying rapid speciation, reticulate and convergent evolution under the arid habitats.