Analysis on the character evolution in Australian Asteraceae based on molecular phylogenetic tree

通过比较核核糖体DNA的内转录间隔区（ITS）和叶绿体DNA的matK基因序列，研究了不同染色体数目的澳大利亚属Calotis（Asteroid）和Gnefosis sensu lato（鼠曲草族）的属内界限和属内关系。在ITS 1区序列的251个位点中，75个位点在16个种间具有变异性，其中39个位点在16个种间具有遗传信息。在matK基因的1206个位点中，有22个位点是可变的，其中5个位点具有遗传信息。DNA数据集分析显示，18个最简约的树ITS 1数据和3个树matK数据选择短尾草作为外群。这两棵树的高引导值支持属的单系性。基于这些树的字符重构表明，染色体数目从n=8减少到n=7，5和4。在ITS 1区的260个位点中，有117个位点是可变的，其中50个位点在广义Gnefosis sensu lato，Tricanthamorphus skirrophora和Epitriche denissus等7种植物中具有遗传信息。分子系统发育树以碎米荠为外类群，表明碎米荠属不是单系的，需要进一步的分类学研究。从Gnephosis drumondii（n=12）到G. tenuissima（n=6）。

The generic circumscription and intra-generic relationships of the Australian genera of Calotis (Astereae) and Gnephosis sensu lato (Gnaphalieae) with various chromosome numbers were examined by the comparison of the sequences of the internal transcribed spacers(ITS) of nuclear ribosomal DNA and the matK gene of chloroplast DNA. Of the aligned 251 sites of ITS 1 Region, 75 sites were variable and 39 of them were phylogenetically informative among 16 species of Calotis. Of the aligned 1206 sites of total matK gene, 22 sites were variable and 5 sites of them were phylogenetically informative. The DNA data sets analyses displayed the 18 most parsimonious trees for the ITS 1 data and three trees for the matK data selected Brachyscome decipiens as outgroup. The monophyly of the genus Calotis was supported with high bootstrap values by both trees. The character reconstruction based on these trees shows that the reduction in chromosome number from n=8 to n=7, 5 and 4. Of the aligned 260 sites of ITS 1 region, 117 sites were variable and 50 of them were phylogenetically informative among seven species of Gnephosis sensu lato, Tricanthodium skirrophora and Epitriche denissus. Molecular phylogenetic tree selected Millotia myosotidifolia as outgroup showed that the genus Gnephosis was not monophyletic and it needed further taxomical re-examination. The reduction in chromosome number from Gnephosis drumondii (n=12) to G. tenuissima (n=6) has been occurred.