叉蕨科的系统发育和生物地理学研究

This project aims to uncover the phylogeny and biogeography of the derived fern family Tectariaceae. This pantropical family comprises about 200 to 300 species of which the waste majority occurs in SE Asia. The family was not generally accepted until 2006 and both the circumscription of the family and the generic classification is still poorly understood. Furthermore, untangling the relationships among members of this family hold the key to improve our understanding of the diversification of derived ferns that are closely related to the two most species rich families of ferns, the Dryopteridaceae and Polypodiaceae. This project aims to resolve three core issues concerning the Tectariaceae: the circumscription of the family,the generic classification, and the global biogeography with focus on continental disjunctions. The first issue includes the morphological definition of the family and the exclusion of species that are not nested in the Tectariaceae, whereas the second issue comprises the determination of genera that compose the Tectariaceae. The third issue concentrates on the colonization of tropical Americas and Eastern Malesia by these ferns, which likely originated in SE Asia. These three issues are addressed using a molecular phylogenetic approach that takes into account the known morphological variation. A dense taxonomic sampling including ca.1/3 of the species diversity and as far as possible material of all putative segregates will be studied using up to four regions of the chloroplast genome and one or two regions of the nuclear genome. The sampling is designed to represent the global species diversity, morphological disparity, and all generic and subgeneric taxa proposed for these ferns in the last 300 years. The analyses are carried out using state-of-the-art analytical tool to reconstruct the phylogenetic relationships,estimate the divergence times, and reconstruct the ancestral biogeographic ranges.

叉蕨科是目前几个缺乏深入研究的世界性类群之一，其系统学研究对理解薄囊蕨类完整的系统发育关系至关重要。该科全世界有8-20属，200-300种，以东南亚和中国大陆的热带亚热带地区多样性最高。叉蕨科植物形态变异复杂，与近缘科间、科下属间及属下种间分类长期存在争议。本项目立足地域优势，并基于前期研究积累，拟利用4个叶绿体片段（atpB、rbcL、rps4-trnS和trnL-F）和2个核基因（LEAFY和gapCp）重建该科的系统发育关系，结合重要形态学性状的分析，建立叉蕨科自然的分类系统；在系统发育框架下进行祖先分布区重建，结合分子钟推算，揭示洲际间断分布格局的成因。我们希望在原有的基础上，对叉蕨科的系统发育和地理分布等问题作更深入的探讨，不仅完善整个薄囊蕨类的系统发育关系，而且可望为探讨蕨类植物洲际间断分布提供一个领先案例。

叉蕨科是一个泛热带分布的科，是目前整个薄囊蕨类中系统发育关系尚存在问题的类群之一，同时也是研究蕨类植物热带洲际间断分布的理想类群之一。本项目通过利用分子和/广义形态证据理清了在该科存在的一些系统学问题，澄清了该科的系统位置、同近缘类群的关系以及科属划分，同时对该科的生物地理分布格局进行了初步分析。主要研究成果概括为以下几点：1）以叉蕨科为切入点，完成了中国蕨类植物的属级生命之树构建，确立了中国蕨类植物新的系统分类框架；2）以分子系统学手段为主，联合形态特征分析和分化时间估算，把爬树蕨属由叉蕨科独立出来，建立了爬树蕨科；3）结合分子证据和形态学分析，确认原叉蕨科成员黄腺羽蕨属应为鳞毛蕨科成员，而原分类学将黄腺羽蕨属和牙蕨属归为近缘类群的形态学特征（两相邻羽片间具有突齿）不具有分类学价值；4）确立了原争议较大的毛脉蕨属的系统位置和分类地位，恢复其属的分类地位；5）发表了桂南爬树蕨的越南新纪录；6）明确了叉蕨科的范畴，叉蕨科现包括6个属，其中中国产2属（叉蕨属和牙蕨属），澄清了叉蕨属及其卫星属的系统关系，支持形态特化的地耳蕨属和沙皮蕨属为叉蕨属成员。7）对叉蕨科的形态演化和生物地理格局开展了初步分析，结果仍在进一步的整理之中。在本项目的基础上，共发表研究论文6篇，其中SCI论文5篇，另有2篇论文在撰写之中。