基于多学科证据探讨樟科油果樟属的系统学问题

The family Lauraceae is one of the primitive angiosperm families with pantropical distribution, and includes ca. 50 genera and 2500-3000 species worldwide. In addition to yielding excellent timber, essential oils, and medicine, trees of the family are important components of tropical and subtropical forests of Asia together with Fagaceae, Magnoliaceae, Hamamelidaceae, and Theaceae, taxonomy of the family thus bears great importance in ecology, floristic biogeography, and biodiversity conservation in the region. However, the family is notorious for its taxonomy. Around 1/3 of total species in China are imperfectly known with either flower or fruit characters wanting. Syndiclis of Lauraceae is a systematically important but poorly studied genus in the subtribe Beilschmiediineae, represented by 10 species and distributed from Tropical India to South China. The genus has large fruits with high content of good quality oils, is thus a potential biomass energy plant group. All 9 species from China are endangered in a recently evaluated RedList using IUCN criteria and categories. But because of lacking specimens (less than 3 collections per species in Herbarium) and special field investigation, variation patterns of key taxonomic characters of the genus remain unclear, and three major taxonomic problems currently exist including species delimitation, subgeneric classification, and systematic position. This project plans to conduct field obvservations and sampling at population level, analyze variation of key morphological characters using analytic tools, investigate leaf cuticular micromorphological characters using light microscope (LM), scanning electron microscope (SEM), and laser scanning confocal microscope (LSCM), study ontogeny of floral organs using SEM, figure out embryological development and its systematic significance, and reconstruct phylogenetic trees based on nrDNA and chloroplast markers. Using multidisciplinary evidence, we try to answer three major systematic questions of Syndiclis, (1) systematic relationships of Syndiclis to closely related genera such as Beilschmiedia, Potameia, Sinopora, and Endiandra based on leaf cuticular micromorphology, floral ontogeny, embryology, and molecular phylogeny, (2) species delimitation by means of population investigation and analyses of variation pattern of key taxonomic characters, (3) subgeneric classification based on combination of morphology, leaf cuticular micromorphology, and molecular evidence. During the last three years, we conducted a few field investigations of the Lauraceae in SE Yunnan, Guangdong, Guangxi, Sichuan, and Guizhou, and collected some materials of the genus and its related genera. Given that favorable financial supports are available, we can conduct a full investigation of the genus and answer the abovementioned scientific questions.

油果樟属由于标本稀少、关键分类特征变异式样不清且缺乏系统的研究，种类界定、属下分类以及该属在樟科中的系统位置均不清楚。本项目拟在野外居群观察取样的基础上，用统计工具分析形态特征的变异式样；用普通光学显微镜、扫描电镜和激光扫描共聚焦显微镜研究油果樟属叶表皮微形态特征的变异式样；用扫描电镜研究花器官形态发生，搞清油果樟属花器官变异式样；用石蜡切片法研究油果樟属的胚胎学特征及其系统学意义；根据分子系统学原理和方法，用核DNA序列和叶绿体DNA序列建立油果樟属的分子系统树。建立特征数据库，用多学科证据分步骤地阐明油果樟属的三个系统学问题：一是通过叶表皮微形态、花器官发生、胚胎学以及分子系统学整合分析，搞清油果樟属与近缘属的关系；二是在居群观察基础上利用统计学方法分析其关键分类特征的变异式样，澄清种的界定问题；三是整合形态、叶表皮微形态和分子系统学数据阐明油果樟属的属下分类。

在项目资助下，我们在云南、贵州、广西、海南、广东、西藏、台湾以及越南和印度尼西亚等地开展了油果樟属及近缘属植物的野外观察、植物标本以及实验材料的采集工作；在野外调查和实验室研究基础上，我们发现了三个新物种；叶表皮结构微形态解剖研究发现樟科的气孔器特征有着重要的分类价值，叶下表皮气孔器周围的表皮细胞有向外隆起形成保护气孔器的结构，在檬果樟属中甚至形成特殊的盖层；花器官发育研究发现油果樟属同轮花器官发育并不同步，而呈现一定的顺序，一些种类花器官结构比较稳定，而一些种类结构极为易变，花被片、雄蕊、腺体以及心皮等的数量和形态变异比较复杂；基于油果樟属的形态、微形态和分子系统学等的研究，建立了油果樟属系统学研究的基础数据集；基于分子和形态数据的联合分析，我们基本搞清了油果樟属的系统学疑难问题，确定了油果樟属与孔药楠属Sinopora J. Li et al.应为同属，油果樟属的模式种Syndiclis paradoxa Hook. f.与中国及中南半岛所产之油果樟属种类不同，依据命名法，我们将油果樟属国产种类及中南半岛之种类组合到孔药楠属中；我们重新界定的孔药楠属与南美洲的三个琼楠属种类关系密切，而与分布于马达加斯加岛的Potameia Thours.属亲缘关系较远，后者与马达加斯加岛的琼楠属种类关系更近，表明琼楠属属群花器官小型化有趋同现象；在分类学研究基础上，结合前人的研究基础和最新研究进展，我们完成了樟科最新物种编目，出版了《中国生物物种名录》樟科部分，完成了《香港植物志》的樟科编研；我们与美国、日本和韩国的植物学家开展了合作研究；参加了瑞典举办的分类学新技能的培训，包括DELTA和Scratchpads等；项目资助培养了两名博士生和三名硕士研究生。项目执行期间，我们共发表了15篇SCI论文（其中含一篇接受），7篇核心期刊论文，共同主编4部专著，编写专著中的4个章节，其中标注了本项目资助的论文有15篇。