我国泥炭藓属两个种复合体的DNA条形码及物种界限研究

Sphagnum, as one of the basal lineages among mosses, has important systematic position and significance in moss evolution. However, morphological taxonomy of Sphagnum is very difficult due to phenotypic plasticity related to environmental factors and frequent hybridization. In particular, species circumscriptions within some complexes of closely related or morphologically similar species fail to reach taxonomic consensus. DNA barcoding technique has been demonstrated to help clarify species delimitation and discover cryptic species. The present proposal plans to conduct extensive filed investigations to collect nine and four Chinese Sphagnum members belonging to S. subsecundum complex and S. recurvum complex, respectively, at the population level. According to previous analysis, seven phylogenetic markers of Sphagnum from plastid genome (rps4, trnL, trnH-psbA) and nuclear genome (RAPDb, RAPDf, LEAFY1, LEAFY2) are chosen for present barcoding and phylogenetic studies in terms of sequencing success and sequence variability. The degree of genetic divergence and cryptic speciation in both of the two species complexes will be tested based on barcoding analysis of variable DNA sequences. The results will provide molecular evidence for resolving taxonomic problems among these closely related species and scientific evidence for selecting specific peatmoss barcodes. Secondly, phylogenetic relationships among members of the two species complexes will be reconstructed based on the same seven DNA regions mentioned above. Divergence time for the major clades of the phylogenetic trees, using a relaxed-clock model, will be also estimated to reveal the origin and diversification of these species. Finally, the current taxonomic systems of S. recurvum complex and S. subsecundum complex will be revised and complemented by new morphological characters, respectively, in combination of DNA data and morphological taxonomy, to provide relatively clear species circumscriptions.

泥炭藓属是藓类植物中最原始的类群之一，具有极其重要的系统地位和进化意义。然而，许多种类表型可塑性强、杂交现象普遍，形态分类十分困难。尤其是一些由近缘种或形态相似种组成的种复合体，种间界限模糊，种的分类学地位长期存在争议。研究表明DNA条形码技术有助于澄清种间界限，揭示隐存种。本项目将针对我国偏叶泥炭藓复合体9种和喙叶泥炭藓复合体4种，分别从居群水平开展野外标本采集。拟从泥炭藓属分子系统学已有报道中，根据DNA序列变异程度选择叶绿体和核基因组来源的7个DNA片段，进行DNA条形码研究，检测种间遗传分化、有无隐存种，为解决疑难种分类学问题提供分子证据，并为筛选能区分泥炭藓属近缘种的特异条形码提供科学依据。同时通过系统发育重建，利用分子钟模型估算物种分歧时间，揭示种间亲缘关系及起源分化。最终，结合DNA证据和形态分类研究，对现有分类指标进行补充、修改，确定种间界限，完成这两个种复合体的分类修订。

泥炭藓属是藓类植物中最原始的类群之一，具有极其重要的系统地位和进化意义。然而，许多种类表型可塑性强、杂交现象普遍，形态分类十分困难。尤其是一些由近缘种或形态相似种组成的复合体，种间界限模糊，种的分类学地位长期存在争议。本项目对我国偏叶泥炭藓复合体和喙叶泥炭藓复合体分别从居群水平开展广泛野外标本采集，获得其地理分布信息。基于分子测序和系统发育重建，揭示偏叶泥炭藓复合体种间的亲缘关系和遗传结构。通过植物模式标本研究，结合分子测序数据与形态特征，基于近年采集的植物样本，并检视《中国苔藓志》中相关凭证标本，初步确定我国有分布的偏叶泥炭藓复合体10种和喙叶泥炭藓复合体3种的分类学地位，为我国泥炭藓属分类学研究提供新的资料。