箭竹属（禾本科、竹亚科）植物的系统发育研究

Fargesia is one of the large genera within Bambusoideae, and is quasi-endemic genus in China. The species in this genus play an important role in forest ecosystem, and are also the main food for giant pandas and some other rare animals. However, the monophyly and the range (including both species and morphological characteristic levels) of the genus remained controversy. Because the reproductive morphological characteristics are totally ignored, the rationality of the infrageneric taxonomic system based on the vegetative morphological characteristics lacks rigorously phylogenetic test. Meanwhile, the relative contributions of the reproductive and vegetative morphological characteristics to the divergence within the genus remains unclear, and the mechanism on the formation of some species complexes due to rapid radiation or the existence of tiny morphological species remains unknown. In the present project, Fargesia will be studied at three levels: (1) to confirm the monophyly and the range by using chloroplast genome sequence data via next generation sequencing (NGS) technique; (2) to establish the phylogenetic framework based on nuclear combined with the chloroplast gene sequence data and to analyze the function of both reproductive and vegetative morphological characteristics served in the infrageneric divergence and the morphological identification characteristics of each clade based on the phylogenetic framework; (3) to investigate the mechanism on the formation of some species complexes based on both the population-based analyses of morphological characteristics and the microsatellite markers developed from NGS data combined with nuclear gene sequence data. Finally, a reasonable phylogenetic-based infrageneric taxonomic system of the genus will be established.

箭竹属是禾本科竹亚科的大属之一，为我国准特有属，其竹种是森林生态系统的重要组成成分，也是大熊猫等珍稀濒危动物的主要食物，但有关该属植物是否为单系类群及其范围争论颇大，忽略繁育器官性状而基于营养器官形态性状建立的箭竹属属下分类系统是否合理，繁育器官和营养器官形态性状在属下多样性形成中的贡献各有多大及一些物种复合体内种的划分等方面均存在问题。因此，本项目拟在三个层次上对箭竹属植物开展研究：通过高通量基因组测序获得叶绿体基因组数据，确定该属的单系性及范围；结合核基因和一些叶绿体基因序列数据建立属下系统发育框架，并探讨繁育器官和营养器官形态性状在属内多样性形成中的作用、不同支系的形态鉴别性状及形态性状的演化规律；以居群为取样单元，借助基因组测序手段开发的微卫星分子标记、核基因数据和形态变异式样探讨一些难于鉴别的物种复合体存在的原因；最终建立该属基于系统发育框架的属下分类系统。

首先，我们完成了18个箭竹属竹种、5个玉山竹属竹种以及5个外类群竹种的叶绿体基因组组装，结合数据库下载的16条相关竹种和玉米、水稻的叶绿体基因组，构建了验证箭竹属单系性的系统发育树，发现基于营养器官形态性状建立的箭竹属并不是一个单系类群。结合分子系统学结果和花序结构，我们建议将玉山竹属和大部分箭竹属竹种合并为广义箭竹属，其在叶绿体基因组序列构建的系统发育树上分为3支：具佛焰苞分支、玉山竹分支和西藏箭竹分支。接下来，我们使用71个箭竹属竹种、39个玉山竹属竹种和16个近缘属竹种的3个叶绿体基因、3个核基因和ITS的序列构建了箭竹属下的分子系统，发现广义箭竹属内大致可划分为具佛焰苞分支、西藏箭竹分支、短锥玉山竹分支、玉山竹分支和海竹分支；进一步分析发现质体捕获、谱系不完全分选以及属内各分支不同程度的杂交/基因渐渗可能是导致箭竹属下核质系统发育树拓扑结构存在冲突的原因。第三，我们使用14个SSR片段在箭竹物种复合体的15个种39个居群750个个体中分析了复合体的遗传多样性、遗传分化和形态性状分化，发现复合体内目前的物种界定与遗传信息聚类结果不符，很可能存在着近期快速的辐射性分化；同时遗传聚类上的分支在营养器官性状上没有显著固定的形态学差异；进一步分析还发现复合体的遗传分化可能与生境海拔、气温和降水量等因素相关。最后，我们统计筛选了广义箭竹属竹种的多个营养器官和繁育器官的形态性状，并基于系统发育关系对关键性状完成了分类学比较和演化趋势分析，归纳了箭竹属下各分支及近缘竹种的繁殖器官的形态变异区分点；总结了形态性状在不同分支的演化趋势。我们整体完成了项目申请时承诺的研究任务，并在部分工作上超额完成；同时针对研究结果中发现的新问题，我们也找到了进一步深入研究的新方向。