东亚伏石蕨属（水龙骨科）的物种形成研究

Speciation as an important stage in evolutionary divergence underlies the formation of biodiversity in the world. Molecular phylogeographic studies have recently begun to elucidate how fern species from their diversification center regions responded to the Quaternary climatic oscillations. Polypodiaceae are the most advanced group of ferns which are mainly epiphytes or lithophytes in Eastern Asian monsoon forests. Study on the mechanisms of diversification of these plants is crucial to understand the evolution of biodiversity in Eastern Asia. Lemmaphyllum as currently circumscribed consists of three closely related sympatric or allopatric species, is a small monophyletic genus of Polypodiaceae. It is a suitable group to study plant speciation. Building up on our phylogenetic and taxonomic research, we propose to use multiple variable plastid DNA markers and single (low) copy nuclear genes (1)to analyze the genetic structure and relationship of DNA haplotypes using phylogeographic approaches; (2)to estimate the spatio-temperal divergence of populations and demographic history applying coalescent-based models and related simulation-based methods; and (3)to compare species distribution simulations and species' niche differentiation on the basis of ecological niche modeling. We aim to explore the speciation and demographic history in the genus Lemmaphyllum, as well as to test morphological species delimitation hypothesis. Furthermore, we will also discuss the relationship between colonization of forest and Quaternary climatic oscillations by combining the published phylogeographic studies concerning forest species in Eastern Asia, and gain better understanding for species diversification of ferns in Eastern Asia by comparing with the relevant research of Lepisorus clathratus complex in Qinghai-Tibetan Plateau.

物种形成与分化是生物多样性形成的基础，是进化生物学的核心问题。水龙骨科植物适应于东亚季风气候和森林植被环境，以附生或石生为主，其物种分化机制对理解东亚植物多样性的形成与演化具有重要意义。该科的伏石蕨属为单系类群，仅含3个近缘种，同域、邻域或异域分布，是探讨物种形成和分化的理想材料。基于系统发育和分类研究的基础，采用多个单亲遗传的叶绿体基因以及双亲遗传的低拷贝核基因，对整个属全分布区的居群材料进行遗传结构、基因谱系地理分析；基于溯祖模拟检测基因流、追溯群体动态历史；基于生态位模型揭示分布区的变化与种群间生态位分化。综合以上结果深入分析该属物种形成机制和分化过程，验证形态物种的划分；结合目前东亚森林物种谱系地理学研究成果，探讨物种形成与森林变迁对第四纪以来地质和气候变化的响应；通过对比青藏高原水龙骨科网眼瓦韦复合体的物种形成和适应机制，全面理解东亚蕨类植物在不同环境下多样性的起源和演化过程。

东亚东南部是世界水龙骨科两大多样性分布中心之一。该科植物以附生为主，适应于热带和亚热带植被生态环境，是探讨该地区蕨类植物物种形成与多样性分化的理想材料。本立项拟采用多个单亲遗传的叶绿体基因和双亲遗传的单（低）拷贝核基因片段，对该地区水龙骨科的代表类群伏石蕨属植物进行遗传结构、谱系地理格局分析；基于溯祖理论，追溯种群动态历史；进行物种分布区模拟，揭示群体的变化规律，探讨伏石蕨属的物种形成机制和过程，及其对第四纪质地气候变化的响应。分析结果显示，伏石蕨属起源于中国西南部地区，总体具有明显的南北分化格局，且青藏高原的快速隆升和随之带来的亚洲季风气候变化可能是导致伏石蕨属产生分化的驱动力，而其分布格局主要可能是由于距离隔离导致。进一步结合该地区相关森林物种的研究，通过比较附生蕨类与森林树种地质气候变化响应的异同，反映了伏石蕨的物种分化与森林变迁具有密切联系。本研究项目的实施对全面理解东亚水龙骨科的多样性起源和演化具有重要的意义。