野牡丹科锦香草属及野海棠属的系统学研究

Phyllagathis and Bredia (Sonerileae-Melastomataceae) are closely related genera with obscure generic circumscription. Approximately 56 and 15 species are recognized in Phyllagathis and Bredia, with 27 and 13 recorded in southern China respectively. Previous studies reveal that the current taxonomy of the aforementioned genera is far from satisfactory: some taxonomic treatments at the species level are rather problematic; circumscription of the two genera, especially for Phyllagathis, remains controversial; and intergeneric relationships among Phyllagathis, Bredia and their close relatives within Sonerileae are yet largely unknown. Major causes leading to these problems include the scantiness of specimens available for study in some species, insufficient field observation and analysis of morphological character variation, and poor knowledge of data from different disciplines with potential systematic value. This project aims to address these problems using multidisciplinary approaches. Through critical survey of literature and herbarium specimen, intensive field observations and examination of morphological, micromorphological, palynological, cytological and molecular systematic characters as well as habitat prefernce and distribution, we will investigate in-depth the variation pattern of these characters and evaluate their taxonomic applicability. Problematic taxonomic treatment at the species level will be revised based on character evaluation with reference to population genetic data. We then reconstruct the phylogeny of Sonerileae with an intensive sampling of Phyllagathis, Bredia as well as the close related genera, using evidence from data from different disciplines. Results of the synthetic phylogenetic analysis will be applied to re-circumscribe Phyllagathis and Bredia, as well as to clarify the phylogenetic relationships among the generic alliances within Sonerileae. This project will resolve in a decisive manner of many phylogenetic controversies of Sonerileae, help us to gain a better understanding of the floristic connection and differentiation between southern China and Indo-Malesian area, and also provide a scientific basis for the utilization and protection of endemic plant resources (both medical and ornamental) in China.

锦香草属和野海棠属是属间界定模糊的近缘属，前者共56种，我国记录27种，后者共15种，我国记录13种。由于缺乏针对性的野外考察，两属现有标本较少，许多具有潜在分类和系统学意义的重要性状如叶表皮、花粉学、细胞学以及分子系统学的研究所涉及的种类也很零星，因此两属在种类的处理、属的界定以及属间关系方面还存在较多问题。本项目拟结合标本室工作、野外考察和实验室研究，对两属主要性状，包括形态学、微形态学、花粉学、细胞学、分子系统学、地理分布和生境进行深入研究，评估并确定其分类和系统学价值，根据性状分析结果及群体遗传学数据完成种级水平的分类学修订，并综合多学科证据重建相关类群的系统发育关系，解决属的界定和属间关系等问题。本项目的开展对解决蜂斗草族的系统学问题十分关键，可以增加对南中国植物区系以及印度-马来西亚植物区系的联系和分化问题的理解，更可为特有植物资源的合理利用及保护提供坚实的科学基础。

野牡丹科蜂斗草族的锦香草属 (Phyllagathis)和野海棠属 (Bredia)在属的界定、属间关系以及物种界定方面还存在较多问题。本项目：1) 分别基于nrITS和叶绿体trnV-M片段、叶绿体基因组、337个单拷贝核基因、以及基因组SNP数据集对锦香草属、野海棠属及其近缘属群进行系统发育重建，以解决属的界定和属间关系；2) 基于系统发育树进行分化时间估算、祖先分布区重建以及属间界定常用形态性状的祖先状态重建；3）分别用1798个单拷贝核基因以及叶绿体基因组，对野海棠属存在物种界定问题的类群进行系统发育分析，同时结合形态性状提出种级修订方案。本项目结果简述如下。锦香草属及野海棠属所在的亚洲蜂斗草族进化枝于中新世（Miocene）从中南半岛一带（Indo-Burma）开始分化并随后扩散至马来半岛-婆罗洲（Malesia）以及东亚（Sino-Japanese）植物区；这一进化枝经历了快速辐射事件，因此nrITS、trnV-M片段、和叶绿体基因组无法解决许多进化枝之间的关系。基于基因组SNP和单拷贝基因数据集的系统发育分析得到了高支持的系统发育树；野海棠属的成员分别与锦香草属物种聚成野海棠枝（Bredia）以及鸭脚茶枝（Tashiroea），我们将其重界定为两个属；锦香草属是超级多系群，该属很可能需要被重界定为一个单种属，其余成员应转移至其他属或处理为独立的属。常用于属间界定的一些性状，如雄蕊、花序、子房冠、胎座轴、以及胎座形态具有极高的同塑性，这解释了目前亚洲蜂斗草族属间界定的混乱现状；生长型、花基数数目、雄蕊排列、果实类型、晶体类型以及透明小腺体的有无具有较低的同塑性，可用作某些进化枝的鉴定特征。野海棠属内存在界定问题的类群中，B. yunnanensis和B. tuberculata应处理为独立的物种，B. latisepala与B. longearistata应予以合并，而B. fordii var. micrantha的贵州独山和广西九万山群体可分别处理为独立的物种，其余群体则为B. esquirolii和B. fordii的成员。本研究为亚洲蜂斗草族迫切的属级修订提供了坚实的系统发育框架，促进了该族的分类与系统学研究，也增加了对南中国植物区系以及印度-马来西亚植物区系的联系和分化问题的理解。