球状绿藻渡边球藻分支的分类学及多样性研究

Watanabea clade is an independent branch in Trebouxiophyceae, Chlorophyta, which was recognized in recent years. Thalli are coccoid single cell, subaerial or aerial, rare aquatic. Up to now, there are 19 species of 11 genera, of which 2 genus and 4 species were first described by our research team. The SSU sequence gaps between the genus of Watanabe clade are more than 100 bps, which is far higher than that of Chlorellales. Our unpublished data show that many sequences from environmental samples represent those of undescribed species belong to this clade, so the clade may has very high species diversity to be found. This project will collect coccoid green microalgae from various aerial and subaerial habitat in China's tropical /subtropical areas, find the hidden diversity in Watanabea clade. The first, we can find habitat distribution Watanabea clade through 18S rDNA metagenomic information. Then we can purify specific algal strains from those positive samples, observe their morphology, life history and ultrastructure. Combined with morphological results and molecular sequence data for phylogenetic analysis, the result can clearly define all genus concept, the exact taxonomy level of Watanabea clade and phylogenetic relationship of the genus among the clade, find the common morphology feature and ecology distribution of Watanabea clade. The project will rich China algal flora, give more knowledge on various evolution lines of unicellular green coccoid algae.

渡边球藻支系是近年才认识的绿藻门共球藻纲一独立支系，植物体为球状单细胞，多气生-亚气生，也见于水体中。已知共11属19种，其中2属和4个种由本学科组首次描述。该分支内，已知成员之间的SSU序列差异较大，相近属间差异超过100个碱基对，远高于小球藻目的属间差异水平。初步数据显示有许多环境样品的序列代表该类群未被描述的物种，该支系可能拥有非常高的物种多样性。本申请将基于我国热带-亚热带多样的生境，进行系统的采集，寻找隐藏的物种多样性。通过宏基因组学方法确定其生境分布信息，再对有效样品进行定向分离纯化，再进行系统的形态学、生活史和超微结构观察，结合形态学结果和多分子标记数据的系统发育分析，对渡边球藻支系进行分类学整理，探讨属间的系统关系。丰富我国淡水藻类区系，界定渡边球藻支系的分类地位、共同形态特征及分布特点，探讨单细胞真核绿藻多样性演化路线。

渡边球藻支系属绿藻门共球藻纲，植物体为球状单细胞，与小球藻非常类似，多见于气生环境，具体分类学地位和概念未定，属间分子差异较大，存在大量未被描述物种。通过室内培养的生活史观察，确定似亲孢子大小异形是渡边球藻分支独特的关键形态学特征，属种间具有胶大的平均遗传距离，结合分子系统学数据将此类群作为一个新目---渡边球藻目提出，并明确了渡边球藻目的范围，绿生球藻属是目外最近缘的独立分支。依据形态数据和分子分子数据，我们还描述了16个新种5个中国新纪录种。.明确了渡边球藻目叶绿体基因组结构特点：都没有反向重复区，不是典型的的四分体架构。种属之间叶绿体基因组共线性很差,存在巨大的差异，多个同源模块发生了倒置和重排。.探讨了驱动雨林中叶附生真核藻类群落组成和多样性的环境因素。对环境18S rDNA序列数据分析表明，绿藻门渡边藻目和橘色藻目占主导，种植林中的叶附生藻类物种丰富度和生物量低于原始雨林和保护雨林。人工林和原始雨林的藻类群落组成存在显著差异，藻类群落结构与森林类型和宿主树种显著相关。