新疆十字花科短命植物系统发育关系及分化时间

Phylogenetic Relationships and Divergence Time of Brassicaceae Ephemeral Plants in Xinjiang

利用核ITS、叶绿体trnL-F（含trnL内含子和trnL-TRNF间隔区）DNA序列，研究分布在新疆的十字花科短命植物的系统发育关系，探讨本区十字花科短命植物与非短命植物之间的系统关系，并利用分子钟原理，估算短命植物的分化时间。主要研究结果如下：短命植物不是单系群，而是聚为多个分支，镶嵌在非短命植物类群中；短命植物分支（属i种）分别与分类学上相近的非短命植物分类单位（近缘属／同属物种）具有很近的系统发育关系，说明短命植物并非单一起源，其分化和发育并未超越属种的演化关系。十字花科短命植物的亲缘关系：涩荠属、丝叶芥属、鸟头荠属、念珠芥属、四齿芥属、绵果荠属、棒果芥属和紫罗兰属亲缘关系较近；离子芥属、脱喙荠属和异果芥属具有较近的亲缘关系；舟果荠属、菘蓝属、厚翅荠属3个属的物种嵌合在一起，并与线果芥属的关系较近；四棱荠属和螺喙荠属系统发育关系很近；庭荠属、独行菜属、高河菜属的短命植物均与同属的物种聚在一起，高河菜属与四棱荠属、螺喙荠属的关系较近。计算表明，涩荠属短命植物的分化时间大致在14-6Ma，即中新世中期至晚期，要早于第三纪末第四纪初的结论。短命植物在这个时间段的分化可能与期间青藏高原的不断隆起密切相关，青藏高原的隆起导致亚洲内陆气候的干旱化以及干旱、半干旱区逐渐形成，促进了短命植物在新疆的进化和发育。

Using nrDNA ITS and cpDNA trnL-F（ combination of trnL intron and trnL-trnF intergenic spacer） DNA sequences, this paper investigated the phylogenetic relationships of the Brassieaceae ephemeral plants in Xinjiang and explored the systematic relationship between ephemeral plants and non-ephemeral plants. The divergennt time of the ephemeral plants was estimated by using molecular clock theory. The main results of the research are as fol- lows： The ephemeral plants are not recovered as a monophyletie group, but rather cluster into several clades which nest in the non-ephemeral plants; The ephemeral groups （genus/species） have close phylogenetic relationships with their taxonomic closely related non-ephemeral units （genus/species from same genus）. The phylogenetie rela- tionships of the ephemeral plants, Malcolmia , Leptaleum , Euclidium , Neotorularia , Tetracme , Lachnoloma , Sterig- mostemum and Matthiola are grouped together, Sterigmostemum and Matthiola are more closely related and they are sister to the lineage comprised of Malcolmia , Leptaleum , Euclidium , Neotorularla , Tetracme and Lachnoloma ; Choris- pora, Litwinowia and Diptychocarpus are closely related; Tauscheria,Isatis and Pachypterygium have close phyloge- netic relationship that members of the three genus nest with each other and they together have close relationship with Conringia ; Goldbachia and Spirorrhynchus unit together and display close phylogenetic status ; The ephemeral plants of Alyssum,Lepidium,Megacarpaea are grouped with the non-ephemeral members from the same genera, separately. It is likely that Megacarpaea is more close to Goldbachia and Spirorrhynchus. The divergent time of the ephemeral plants is estimated between 14 -6 Ma that is the middle to the late Miocene which is earlier than the previous esti- mation of from the late Miocene to the early Pliocene. The intensive divergence of the ephemera plants in the mid- dle and the late Miocene might be closely related with the uplift of Qinghai - Xizang plateau which caused aridifica- tion in the central Asia and speed up the formation of arid and semi-arid climate and the development of the ephem- eral plants in the area.