实验海洋生物学重点实验室知识库

囊藻属 (Colpomenia) 隶属于Orchorophyta门、褐藻纲 (Phaeophyceae)、墨角藻亚纲(Fucophycidae)、水云目 (Ectocarpales)、萱藻科 (Scytosiphonaceae)。该属在全球范围内分布十分广泛，多附生于中低潮间带的岩石或大型海藻上。囊藻属藻体直立，呈中空的囊形或球形。由于具有随水流长距离扩散和附着在贝壳（如牡蛎）上跨地区扩散的特征，因此囊藻属海藻是研究海洋生物多样性变动、种群遗传变异和生物地理格局形成的良好模型。目前，中国境内关于囊藻属物种的记载只有长囊藻(C. bullosa，最新的系统分类研究将其更名为Dactylosiphon bullosus) 和囊藻 (C. sinuosa)，详细的物种多样性组成和地理分布研究尚为空白。本研究利用线粒体cox3和atp6标记对我国近海囊藻属物种进行系统分类和种群遗传结构分析，厘清了中国近海囊藻属物种组成、各自地理分布规律以及外来囊藻（C. peregrina）种群多样性特征与遗传变异模式。主要结果如下：
⑴利用线粒体cox3和atp6序列对我国近海30个采样点的63个囊藻属样本进行系统分类和遗传变异分析。通过PCR扩增和正向测序获得63条cox3基因序列（620 bp）和62条atp6基因序列（611 bp）。基于最大似然法 (Maximum Likelihood, ML)和贝叶斯法 (Bayesian Inference, BI) 构建的进化树均显示中国近海的囊藻属分化为3个独立分支。Cox3和atp6标记均显示进化树内3个分支间的遗传距离较高，而分支内遗传距离较低。结合形态观察证据和进化树结构，我们认为中国近海囊藻属包括3个种：C. claytoniae, 外来囊藻 (C. peregrina) 和囊藻 (C. sinuosa)，其中外来囊藻和C. claytoniae在中国属于新记录种。囊藻主要分布在广西、广东和海南等地，外来囊藻主要分布在黄渤海，最南至浙江的南麂列岛及附近。C. claytoniae则有限的分布在东海和南海沿岸和岛屿（南麂列岛、涠洲岛和海南岛）。因栖息地破坏，原记载分布于中国辽宁和山东近海的长囊藻可能已消失。
⑵利用线粒体cox3和atp6序列研究了我国近海外来囊藻 (C. peregrina) 13个地理种群的多样性特征和遗传结构。PCR扩增获得302条cox3序列（620 bp）和310条atp6序列（611 bp），其中cox3序列产生26个单倍型， atp6序列产生17个单倍型。基于两个标记的系统进化、遗传多样性、单倍型网络和Fst值均显示中国近海的外来囊藻种群已分化成3个遗传世系，其中浙江南麂列岛的7个种群遗传多样性较高。
本研究首次利用分子系统学手段对我国囊藻属进行系统分类和多样性研究，揭示海藻遗传分化和物种形成规律，相关结果有利于提升我们对中国近海海藻多样性和分布特征的认知，并为潮间带海洋物种多样性保护提供科学依据。

Colpomenia taxonomically belongs to Scytosiphonaceae, Ectocarpales, Fucophycidae, Phaeophyceae, Orchorophyta. Species in the genus mainly occur in the middle or lower intertidal zone, mostly growing attached to rocks or attached to other macroalgae, shaped as hollow sacs or spheres. Species of this genus are widely distributed worldwide because of the character that can travel over long-distances with water flow or attach to shells (such as oysters), so the genus can be ideal model to study biodiversity trends, population genetic structure and biogeographical patterns of seaweeds. At present, only C. sinuosa and C. bullosa (renamed Dactylosiphon bullosus in latest classification) have been recorded in China, and the study on species diversity and geographical distribution is still blank. In this study, we analyzed the phylogenetic relationship and population genetic structure base on mitochondrial cox3 and atp6 markers, and identified species and geographical distribution of Colpomenia along the coast of China, as well as the population diversity characteristics and genetic variation pattern of C. peregrina. The main results are as follows:
(1) Phylogenetic relationship and genetic variation were analyzed based on 63 individuals from 30 localities along the coast of China. We obtained 63 cox3 gene sequences (620 bp) and 62 atp6 gene sequences (611 bp) by PCR amplification and sequencing. Three independent phylogenetic clades were seperated based on Maximum Likelihood (ML) and Bayesian Inference (BI). Meanwhile, both cox3 and atp6 markers showed high genetic distance among the clades and low genetic distance within each clade. Combining with morphological data, we suggest that the Colpomenia mainly consists of three species along the coast of China: C. claytoniae, C. peregrina and C. sinuosa, among which C. claytoniae and C. peregrina are newly recorded in China. Colpomenia sinuosa is mainly distributed in the coastal areas of South China Sea, such as Guangxi, Guangdong and Hainan. Colpomenia peregrina was mainly found in the Yellow-Bohai Seas, and as far south as the Nanji islands in Zhejiang province. Colpomenia claytoniae occurred on isolated islands in the East and South China Seas (Nanji islands, Weizhou island and Hainan island). Due to habitat destruction, C. bullosa (now renamed Dactylosiphon bullosus), which was recorded in Liaoning and Shandong, may have disappeared in recent years.
(2) The diversity and population genetic structure in 13 geographic populations of C. peregrina were studied using mitochondrial cox3 and atp6 sequences. We obtained 302 cox3 sequences (620 bp) and 310 atp6 sequences (611 bp), in which 26 cox3 haplotypes and 17 atp6 haplotypes were generated. Phylogenetic relationship, genetic diversity, haplotype network and Fst values based on the two markers all suggested that there were three genetic lineages among C. peregrina populations in the coast of China, and seven populations in the Nanji islands of Zhejiang showed higher genetic diversity.
This research combined molecular and morphological data to study phyologenic taxonomy and biodiversity of Colpomenia along the coast of China, which is helpful to improve the knowledge of present algal diversity and distribution range. The results not only reveal and enrich the theory of genetic differentiation and speciation of seaweeds in the Northwest Pacific, but also provide scientific evidence for marine biodiversity conservation in intertidal zone.