中国西南地区膜叶铁角蕨属的多倍体起源和网状进化研究

项目名称： 中国西南地区膜叶铁角蕨属的多倍体起源和网状进化研究

项目编号： No.31500171

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 生物科学

项目作者： 常艳芬

作者单位： 衡阳师范学院

项目金额： 20万元

中文摘要： 膜叶铁角蕨属约30余种，具有丰富的细胞倍性和多样的繁殖方式，是进化生物学研究中不可多得的模式类群。中国西南地区是膜叶铁角蕨属的物种多样化中心及可能的起源和分化中心。本研究拟重点以中国西南地区分布的膜叶铁角蕨属植物为研究对象，应用多学科研究手段，综合形态学、细胞学和遗传学数据，并结合地理分布格局和生境特征，全面深入地研究中国西南地区膜叶铁角蕨属多倍体类群的起源及可能的网状进化模式。本项目的研究结果最终将可能揭示该类群植物在染色体数目、繁殖方式、生境适应及形态特征等方面进化适应上采取的不同分子进化策略，并解释其丰富的多样性形成的原因。本研究还将为探讨膜叶铁角蕨属的系统演化和物种分类提供新的线索和较完全的信息，并为铁角蕨类植物物种形成和进化机制的研究提供重要证据。

中文关键词： 蕨类植物；复合体；分子标记

英文摘要： Hymenasplenium was recognized as a genus in the present generic delimitation of the family Aspleniaceae. It is a well-defined group with unusual dorsiventral vascular system in long creeping rhizomes and chromosome base numbers differing from typical of Asplenium of x=36. Members of Hymenasplenium are widely distributed in the tropic zones of the world. Southwestern China is the place with the highest diversity of Hymenasplenium species. Moreover, cytologically and reproductively abundant basal forms of Hymenasplenium exist in Southwestern China supporting the assumption that this region is a diversity center of the genus. The Asian members of Hymenasplenium have been extensively investigated particularly in cytology. Polyploidy is common in Hymenasplenium and reticulate evolution is suggested, making this fern group a good model for study of plant systematics and evolutionary biology. Besides, Hymenasplenium can be one of the best materials for studying the evolutionary and ecological significance of sexual reproduction because several pairs of sexual and apogamous races are known. The species classification and evolution of Hymenasplenium, however, is still poorly known. To know the polyploidy origin and reticulation of Hymenasplenium have a major importance when studying the complex evolution of this genus which is well known of its great variation in cytology, morphology and ecology. In our previous studies, phylogeny and reticulation of the Asplenium normale complex were successfully revealed by using four regions of the maternally inherited chloroplast genome and one biparentally inherited marker, the single-copy nuclear gene pgiC, and determining ploidy levels of samples by measuring spore size and determining DNA C-values by flow-cytometric analysis of selected specimens. Therefore, we hypothesized that ploidy levels and DNA sequencing studies, particularly comparisons of phylogenetic analyses of nuclear and chloroplast sequences among polyploids and their proposed progenitors, can reveal reticulate evolutionary patterns and resolve taxonomic challenges in Hymenasplenium. In this study, we plan to focus on the polyploidy origin and reticulation of Hymenasplenium in Southwestern China. We will infer ploidy level from spore measurements, flow-cytometric analysis and chromosome observation. We will assess reproductive mode by counting spore numbers per sporangium. Then we will use sequences from plastid regions and two single copy genes to infer polyploidy origin and reticulation from incongruence between gene trees and from cloning and sequencing duplicated loci in polyploidies. The results of this research will provide insight into the evolutionary strategies and causes of variations in Hymenasplenium in Southwestern China. Finally, our study will help to understand speciation processes and evolution of Hymenasplenium and contribute to the debate about the taxonomy of this genus.

英文关键词： Pteridophytes;Species complex;Molecular markers