我国北方岩溶泉域刚毛藻的系统发育及形态学研究

脆弱刚毛藻(Cladophora fracta)是一种大型丝状绿藻,生境分布广泛。然而,对于岩溶泉域分布的刚毛藻研究较少,它们的遗传多样性、生物地理亲缘性和生理特性都有待于深入研究。该研究对我国北方地区五个典型岩溶泉域的50个脆弱刚毛藻样本进行了形态学和分子系统学描述。主要研究目标:(1)对我国北方地区五个典型岩溶泉的刚毛藻生境进行描述;(2)根据形态学特征和分子序列对藻体进行鉴定;(3)探究生境对藻体生理特性的影响。结果表明:基于SSU和LSU序列的结果,发现所分析的50株刚毛藻个体为同一种,同时还发现了13个不同的核糖体基因型。基于SSU和LSU的系统发育树,刚毛藻属均未能形成单系分支,分布在三个不同的分支上。13个样本基因型在SSU和LSU树中的位置相似,与Cladophora vagabunda有很高的序列同源性,但是形态特征却差异很大。从显微结构结果来看,五个岩溶泉域采集到的刚毛藻在细胞直径上无显著差异,藻体的形态特征与脆弱刚毛藻相一致。但是,岩溶泉域采集的藻体细胞直径比文献报道中在湖泊和河流中采集的脆弱刚毛藻直径要大。另外,仅在两个地点(XA和ST)采集的标本中发现有假根状分枝。因此,基于形态学和分子序列的结果,将这五个泉域的刚毛藻鉴定为脆弱刚毛藻(Cladophora fracta)。     

淡水刚毛藻目一新组合种及其系统发育分析

作者于2012-2014年先后在湖北省采集到4株刚毛藻目的丝状绿藻。经鉴定,其形态特征和莫拉瓦刚毛藻Cladophora moravica Gardavsk(1986)非常相似;但相较于刚毛藻属各个种的形态,4株藻体更接近黑孢藻科的分类特征。基于SSU和LSU rDNA序列构建的系统发育树显示,4株刚毛藻目的丝状绿藻均属于黑孢藻科拟湖球藻属(Aegagropilopsis)。据此,作者建议将该种名称作为一个新组合处理,即莫拉瓦拟湖球藻Aegagropilopsis moravica(Dvoˇrák)Zhao et Liu com.nov。拟湖球藻属仅含有3个种:莫拉瓦拟湖球藻、硬枝拟湖球藻和棒状拟湖球藻,其形态特征与湖球藻相近且易混淆,故采用核基因组序列分析方法区分二者是非常有效的。     

西太平洋浮游有孔虫Globigerinita glutinata种内SSU rDNA多样性研究

有孔虫分子鉴定和分子多样性研究多基于SSU rDNA序列片段分析,但某些浮游种内可能存在基因组内rDNA变化,影响分类学和分子生态学的研究结果。为了研究浮游有孔虫物种内是否存在rDNA多样性,本工作以采自热带西太平洋的浮游有孔虫Globigerinita glutinata活体标本作为研究对象,经形态学鉴定后,利用单细胞PCR和克隆技术,获得5个虫体的20条SSU rDNA目的片段(300—400 bp),同时对其序列结构进行了研究。结果显示,同种G.glutinata出现了四类不同的SSU rDNA核酸类型。序列成对分析显示,该种遗传距离差异最长可达0.249,远高于其它物种。此外,同一样本不同克隆片段中,出现了高达四个不同的SSU rDNA核酸型。序列的差异主要集中在三个不同的高变异区,高可变区的长度范围为21 bp到63 bp。从差异序列的间隔分布推断,核糖体基因簇的重组可能是不同SSU rDNA核酸型出现的原因。本工作在国内首次揭示了热带西太平洋浮游有孔虫G.glutinata种内的SSU rD NA核酸型,研究结果表明G.glutinata的种内SSU rDNA变异性极大,复杂的生活史以及假基因的存在或许是造成该现象的原因。     

两株不同地域的家蚕微孢子虫分离株的细胞侵染力 比较及遗传多样性分析

家蚕微孢子虫(Nosema bombycis)是蚕业生产上一种毁灭性病害—— 微粒子病的病原体。文章将安徽和重庆两地域来源的病原性家蚕微孢子虫分离株进行草地贪夜蛾Sf9细胞感染性检测, 结果显示二者对细胞的侵染能力存在显著差异。为进一步探讨不同家蚕微孢子虫分离株的种群多态性, 进行了孢子虫核糖体DNA序列的测定和系统聚类比较, 结果表明SSU rDNA(Small subunit ribosomal DNA)和ITS(Internal transcribed spacer)在不同地域的种群差异性并不显著。通过检索重庆株全基因组数据及其他地域株rDNA序列, 显示在家蚕微孢子虫rDNA元件的部分SSU rDNA结构复制子中存在MITE-like转座元件的插入, 表明家蚕微孢子虫rDNA结构的多样性。     

一株淡水多甲藻的形态观察和多甲藻属系统发育分析

通过形态学方法将中国淡水藻种库一株编号为FACHB-329的甲藻鉴定为楯形多甲藻不等变种Peridinium umbonatum var.inaequale Lemmermann,并且描述了此甲藻所产生的孢囊形态。还对该藻的SSU和LSU rDNA序列进行测序,系统发育分析的结果也支持形态鉴定。系统发育研究结果表明多甲藻属是多系起源的,本研究所用的多甲藻属类群可以形成两个大的分枝——Peridinium umbonatum类群形成的分枝和狭义多甲藻属类群（Peridinium sensu stricto）形成的分枝。并且形态学和分子数据都显示了P.umbonatum类群与狭义多甲藻属类群之间的差异。P.umbonatum类群形成的淡水单系类群虽然没有高度的自展支持但获得了不同的系统发育分析的支持,而狭义多甲藻属类群形成的单系类群获得了高度的支持。淡水多甲藻P.aciculiferum和P.wierzejskii则与海洋斯氏藻属关系密切。     

基于LSU和ITS的青藏高原黄绿卷毛菇种群遗传多样性分析

为研究黄绿卷毛菇群体遗传结构,以青海、西藏、四川3个省份的10个地理群共91个样本黄绿卷毛菇为实验材料,采用分子生物学方法测定和分析所有样本的LSU和ITS序列。结果显示:1 995bp的LSU和ITS基因序列共有8个变异位点,得到20个基因型。单倍型多样性指数(Hd)和核苷酸多样性指数(pi)分别为0.538±0.026和0.00029±0.00002;青海玉树和青海兴海的遗传多样性指数最高。分子变异分析结果表明黄绿卷毛菇群体遗传变异主要来自种群内(75.70%),种群间遗传分化较大。系统进化树结果也表明,10个地理群分成2个支系,黄绿卷毛菇群体存在明显的地理结构。中性检测结果进一步证实,黄绿卷毛菇群体有着复杂的群体历史,曾发生过种群数量扩张,近期种群数量正在衰减。     

采自青海湖的刚毛藻属一新种——青海刚毛藻

对青海湖的丝状藻类进行了样品采集, 分析引起水华的藻类种类和组成。基于SSU-LSU的联合进化分析和基于ITS的系统进化分析显示: 形成青海湖水华的丝状藻为一种刚毛藻, 该种与史氏刚毛藻Cladophora stimpsonii和散束刚毛藻Cladophora vagabunda具有较近的亲缘关系, 属于海洋刚毛藻和淡水刚毛藻的中间过渡种类。和邻近种类的区别特征如下: 该种生长于咸水生境, 植物体纤细柔软, 呈绿色或浅绿色, 分枝旺盛, 具明显的顶端生长和居间生长。细胞直径较小。主轴细胞直径30.0—90.0 μm, 细胞长宽比2.4—8.0。分枝细胞直径25.0—70.0 μm, 长宽比4.0—12.3。顶端细胞直径25.0—50.0 μm, 长宽比3.6—12.0。基于形态学特征和分子系统发育分析, 将其定为一新种, 即青海刚毛藻Cladophora qinghaiensis sp. nov.。     

石斑角形虫(黏体门, 角形虫科)的分子证据及其在不同宿主中的遗传变异

研究从中国东海的青石斑鱼 Epinephelus awoara Temminck & Schlegel 1842和褐带石斑鱼E. bruneus Bloch 1793的胆囊中检获了石斑角形虫 Ceratomyxa epinephela Wu, Wu et hua, 1993, 首次提供了其SSU rDNA和ITS1 rDNA序列, 并基于形态学和分子数据进行了重新描述。石斑角形虫成熟孢子的孢子长(4.8±0.5) μm (3.6—5.6 μm), 孢子厚(31.8±4.8) μm (23.3—37.5 μm); 孢子壳瓣光滑且等大, 由垂直的缝线连接; 极囊长(2.9±0.2) μm (2.4—3.7 μm), 极囊宽(2.6±0.2) μm (2.2—3.1 μm); 孢子夹角处稍微凹陷, 延伸至两端逐渐变平坦, 夹角为 (175.9±3.7)° (165.5°—179.7°)。基于SSU rDNA序列构建的系统发育树显示石斑角形虫与诺兰角形虫C. nolani Gunter & Adlard 2009, 卡特莫尔角形虫C. cutmorei Gunter & Adlard 2009和横山角形虫C. yokoyamai Gunter & Adlard 2009 有很近的亲缘关系, 且其宿主均为石斑鱼属物种。结果表明, 类群关系较近的宿主其寄生的同属黏孢子虫可能具有更近的系统发育关系。基于SSU rDNA和ITS1 rDNA的遗传分析显示, 石斑角形虫的4个分离株已发生了明显的遗传分化(形成了4个基因型), 形成了不同的种群, 但在不同宿主种类间并未形成特有的分化。     

广东鉴江水系底栖硅藻多样性与时空分布特征

为了解广东省鉴江水系底栖硅藻多样性和时空分布特征,对全流域进行了底栖硅藻采样调查。结果表明,从19个采样点4次采样中共检出底栖硅藻10科52属242种,其中舟形藻属(Navicula)、菱形藻属(Nitzschia)和异极藻属(Gomphonema)是优势类群,出现频次和相对丰度较高。硅藻多样性指数(丰富度、真香农多样性指数和真辛普森多样性指数)随河流等级呈现一定的空间分布特征,但它们季节变化不明显。底栖硅藻群落相异性在上游和下游河段较高,从一级到三级河流递减,四级河流又增加。底栖硅藻群落结构空间变化明显,季节变化显著。群落丰富度的稀疏曲线表明,热带河流底栖硅藻群落以400个体计数,不能完整反映底栖硅藻多样性。这些为鉴江水系河流健康监测和水生态保护奠定了基础。     

Toward a better understanding of the infrageneric relationships in Cortinarius (Agaricales, Basidiomycota)

Research on the molecular systematics of Cortinarius, a species-rich mushroom genus with nearly global distribution, is just beginning. The present study explores infrageneric relationships using rDNA ITS and LSU sequence data. One large dataset of 132 rDNA ITS sequences and one combined da-taset with 54 rDNA ITS and LSU sequences were generated. Hebeloma was used as outgroup. Bayesian analyses and maximum-likelihood (ML) analyses were carried out. Bayesian phylogenetic inference performed equally well or better than ML, especially in large datasets. The phylogenetic analysis of the combined dataset with species representing all currently recognized subgenera recovered seven well-supported clades (Bayesian posterior probabilities BPP > 90%). These major clades are: /Myxacium s.l., /subg. Cortinarius, the /phlegmacioid clade (including the subclades /Phlegmacium and /Delibuti), the /calochroid clade (/Calochroi, /Ochroleuci and /Allutus), the /telamonioid clade (/Telamonia, /Orellani, /Anomali), /Dermocybe s.l. and /Myxotelamonia. Our results show that Cortinarius consists of many lineages, but the relationships among these clades could not be elucidated. On one hand, the low divergence in rDNA sequences can be held responsible for this; on the other hand, taxon sampling is problematic in Cortinarius phylogeny. Because of the incredibly high diversity (~2000 Cortinarius species), our sampling included <5% of the known species. By choosing type species of subgenera and sections, our sampling is strongly biased toward Northern Hemisphere taxa. More extensive taxon sampling, especially of species from the Southern Hemisphere, is essential to resolve the phylogeny of this important genus of ectomycorrhizal fungi.     

Phylogenetic analysis of ribosomal RNA operons from uncultivated coastal marine bacterioplankton

Analyses of small subunit ribosomal RNA genes (SSU rDNAs) have significantly influenced our understanding of the composition of aquatic microbial assemblages. Unfortunately, SSU rDNA sequences often do not have sufficient resolving power to differentiate closely related species. To address this general problem for uncultivated bacterioplankton taxa, we analysed and compared sequences of polymerase chain reaction (PCR)-generated and bacterial artificial chromosome (BAC)-derived clones that contained most of the SSU rDNAs, the internal transcribed spacer (ITS) and the large subunit ribosomal RNA gene (LSU rDNA). The phylogenetic representation in the rRNA operon PCR library was similar to that reported previously in coastal bacterioplankton SSU rDNA libraries. We observed good concordance between the phylogenetic relationships among coastal bacterioplankton inferred from SSU or LSU rDNA sequences. ITS sequences confirmed the close intragroup relationships among members of the SAR11, SAR116 and SAR86 clades that were predicted by SSU and LSU rDNA sequence analyses. We also found strong support for homologous recombination between the ITS regions of operons from the SAR11 clade.     

New taxa refresh the phylogeny and classification of pleurostomatid ciliates (Ciliophora,Litostomatea)

A high diversity of pleurostomatid ciliates has been discovered in the last decade, and their systematics needs to be improved in the light of new findings concerning their morphology and molecular phylogeny. In this work, a new genus, Protolitonotus gen. n., and two new species, Protolitonotus magnus sp. n. and Protolitonotus longus sp. n., were studied. Furthermore, 19 novel nucleotide sequences of SSU rDNA, LSU rDNA and ITS1‐5.8S‐ITS2 were collected to determine the phylogenetic relationships and systematic positions of the pleurostomatid ciliates in this study. Based on both molecular and morphological data, the results demonstrated that: (i) as disclosed by the sequence analysis of SSU rDNA, LSU rDNA and ITS1‐5.8S‐ITS2, Protolitonotus gen. n. is sister to all other pleurostomatids and thus represents an independent lineage and a separate family, Protolitonotidae fam. n., which is defined by the presence of a semi‐suture formed by the right somatic kineties near the dorsal margin of the body; (ii) the families Litonotidae and Kentrophyllidae are both monophyletic based on both SSU rDNA and LSU rDNA sequences, whereas Amphileptidae are non‐monophyletic in trees inferred from SSU rDNA sequences; and (iii) the genera Loxophyllum and Kentrophyllum are both monophyletic, whereas Litonotus is non‐monophyletic based on SSU rDNA analyses. ITS1‐5.8S‐ITS2 sequence data were used for the phylogenetic analyses of pleurostomatids for the first time; however, species relationships were less well resolved than in the SSU rDNA and LSU rDNA trees. In addition, a major revision to the classification of the order Pleurostomatida is suggested and a key to its families and genera is provided.     

Molecular phylogeny of the Cladophoraceae (Cladophorales,Ulvophyceae), with the resurrection of Acrocladus Nägeli and Willeella Børgesen,and the description of Lurbica gen. nov. and Pseudorhizoclonium gen. nov.

The taxonomy of the Cladophoraceae, a large family of filamentous green algae, has been problematic for a long time due to morphological simplicity, parallel evolution, phenotypic plasticity, and unknown distribution ranges. Partial large subunit (LSU) rDNA sequences were generated for 362 isolates, and the analyses of a concatenated dataset consisting of unique LSU and small subunit (SSU) rDNA sequences of 95 specimens greatly clarified the phylogeny of the Cladophoraceae. The phylogenetic reconstructions showed that the three currently accepted genera Chaetomorpha, Cladophora, and Rhizoclonium are polyphyletic. The backbone of the phylogeny is robust and the relationships of the main lineages were inferred with high support, only the phylogenetic position of both Chaetomorpha melagonium and Cladophora rupestris could not be inferred unambiguously. There have been at least three independent switches between branched and unbranched morphologies within the Cladophoraceae. Freshwater environments have been colonized twice independently, namely by the freshwater Cladophora species as well as by several lineages of the Rhizoclonium riparium clade. In an effort to establish monophyletic genera, the genera Acrocladus and Willeella are resurrected and two new genera are described: Pseudorhizoclonium and Lurbica.     

Cyst‐motile stage relationship and molecular phylogeny of a new freshwater dinoflagellate Gymnodinium plasticum from Plastic Lake,Canada

The dinophyceaen genus Gymnodinium was established with the freshwater species G. fuscum as type. According to Thessen et al. (2012), there are 268 species, with the majority marine species. In recently published molecular phylogenies based on ribosomal DNA sequences, Gymnodinium is polyphyletic. Here, a new freshwater Gymnodinium species, G. plasticum, is described from Plastic Lake, Ontario, Canada. Two strains were established by incubating single cysts, and their morphology was examined with light microscopy and scanning electron microscopy. The cyst had a rounded epicyst and hypocyst with a wide cingulum and smooth surface. Vegetative cells were characterized by an elongated nucleus running vertically and a deep sulcal intrusion. The apical structure complex was horseshoe‐shaped and consisted of two pronounced ridges with a deep internal groove, encircling 80% of the apex. Small subunit ribosomal DNA (SSU rDNA), large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer (ITS) sequences were obtained from cultured strains. Molecular phylogeny based on concatenated SSU, LSU and ITS sequences supports the monophyly of the Gymnodiniales sensu stricto clade but our results suggest that many Gymnodinium species might need reclassification. Gymnodinium plasticum is closest to Dissodinium pseudolunula in our phylogeny but distant from the type species G. fuscum, as are the other gymnodiniacean taxa.     

Molecular,biochemical and morphological data suggest an affiliation of Spongiochrysis hawaiiensis with the Trentepohliales (Ulvophyceae,Chlorophyta)

The aeroterrestrial, unicellular green alga Spongiochrysis hawaiiensis had been included in the ulvophycean order Cladophorales based on small subunit (SSU) rDNA sequence data, and represents so far the only fully terrestrial member of this order. Other characteristics of S. hawaiiensis that are atypical for Cladophorales include the presence of large amounts of carotenoids and a budding‐like mode of cell division. As the position of this terrestrial, unicellular alga in an order of aquatic, multicellular green algae is unusual, we re‐evaluated the phylogenetic relationships of this enigmatic organism based on supplementary SSU rDNA sequences as well as novel large ribosomal subunit (LSU) rDNA and internal transcribed spacer (ITS rDNA) sequences. Additionally, we examined several morphological characters of S. hawaiiensis, as well as low molecular weight carbohydrate (LMWC) patterns of S. hawaiiensis and members of the Cladophorales and Trentepohliales as potential chemotaxonomic markers. We found S. hawaiiensis to be uninucleate. The analysis of the LMWC content detected the presence of the polyol erythritol in S. hawaiiensis and in the Trentepohliales, while this compound was missing in the Cladophorales. The phylogenetic analyses of the novel sequences placed S. hawaiiensis in the terrestrial Trentepohliales. This placement is supported by the aeroterrestrial habitat, the presence of large amounts of carotenoids, the uninucleate cells, and the presence of the polyol erythritol as a protective compound against water loss.     

Hidden diversity in high-latitude Southern Hemisphere environments: Reinstatement of the genus Rama and description of Vandenhoekia gen. nov. (Cladophoraceae,Ulvophyceae, Chlorophyta), two highly variable genera

The continental coasts and remote islands in the high-latitude Southern Hemisphere, including the subantarctic region, are characterized by many endemic species, high abundance of taxa, and intermediate levels of biodiversity. The macroalgal flora of these locations has received relatively little attention. Filamentous green algae are prolific in the intertidal of southern islands, but the taxonomy, distribution, and evolutionary history of these taxa are yet to be fully explored, mostly due to the difficulty of access to some of these locations. In this study, we examined specimens of the order Cladophorales from various locations in the high-latitude Southern Hemisphere including the subantarctic (the Auckland Islands, Bounty Islands, Campbell Island, Macquarie Island, and Kerguelen Islands), as well as mainland New Zealand, the Chatham Islands, Chile, and Tasmania. The analyses of the rDNA sequences of the samples revealed the existence of two new clades in a phylogeny of the Cladophoraceae. One of these clades is described as the novel genus Vandenhoekia gen. nov., which contains three species that are branched or unbranched. The amended genus Rama is reinstated to accommodate the other clade, and contains four species, including the Northern Hemisphere “Cladophora rupestris.” In Rama both branched and unbranched morphologies are found. It is remarkable that gross morphology is not a predictor for generic affiliations in these algae. This study illustrates that much can still be learned about diversity in the Cladophorales and highlights the importance of new collections, especially in novel locations.