基于nrITS、psbA-trnH和DMC1序列中国短柄草族的系统进化和生物地理学研究

短柄草族（Brachypodieae）有短柄草（Brachypodium sylvaticum）和二穗短柄草（Brachypodium distachyum）两种模式植物，具有重要科研价值，与雀麦族（Bromeae）和小麦族（Triticeae）的系统位置关系尚不明确。据此，本文运用最大简约法（MP）、最大似然法（ML）和贝叶斯推断法（BI）对叶绿体基因片段psbA-trnH、核糖体基因转录间隔区ITS、单拷贝核基因片段DMC1以及psbA-trnH+nrITS+DMC1联合序列数据进行分析，来揭示三者的系统学位置关系。研究结果表明，在DMC1、nrITS以及联合基因序列构建的系统进化树中，短柄草族、雀麦族、小麦族各自聚为一支，且具有较高的支持率；在叶绿体基因psbA-trnH构建的系统进化树中，短柄草族聚为一支，雀麦族分散镶嵌在小麦族中，提示小麦族、雀麦族之间发生了多种进化情况。利用BEAST和RASP对psbA-trnH+nrITS+DMC1联合序列分析，结果表明：小麦族起源于西北地区，物种形成时间多集中在13-7 Ma，与青藏高原中新世中晚期（13-7 Ma）的隆起一致；短柄草族起源于西南地区，物种形成时间多集中在3 Ma之后，这与东亚季风的加强和青藏高原上新世以来的剧烈抬升时间一致，中国特有种草地短柄草（Brachypodium pratense）也是在该时间段分化形成。

Phylogeny and Biogeography Studies of Brachypodieae from China Based on nrITS,psbA-trnH and DMC1 Genes

Brachypodieae have two model plants, Brachypodium distachyum and Brachypodium sylvaticum, with important research value. Brachypodieae also have some problems in the systematic position with Bromeae and Triticeae. We used maximum parsimony, maximum likelihood and Bayesian inference to analyze the relationship of three tribes, basing on sequences of DMC1, nrITS, psbA-trnH and DMC1+psbA-trnH+nrITS. The phylogenetic trees respectively basing on sequences of DMC1, nrITS and DMC1+psbA-trnH+nrITS revealed that Brachypodieae, Bromeae and Triticeae fell into three separate clades. The phylogenetic trees basing on sequences of psbA-trnH show that Bromeae and Triticeae formed a one single clade. The results showed that Bromeae and Triticeae have experienced complex evolution. We estimate divergence times with BEAST, and reconstruct ancestral state with RASP. The result showed that Triticeae in china originated in northwest region,Species divergence time focused on 13-7 Ma which is consistent with the change of the cretaceous period in the Tibetan plateau. Brachypodieae in china originated in southwest region, species divergence time focused on 3 Ma which is consistent with the change of the Pliocene period in the Tibetan plateau and the change of East Asian summer monsoon(EASM). Brachypodium pretense differentiation also occurred at this period.