Morphogenesis of Pistillate Flowers of Cercidiphyllum japonicum(Cercidiphyllaceae)

Floral morphogenesis and the development of Cercidiphyllum japonicum Sieb.et Zucc.were observed by scanning electronmicroscopy(SEM).The results showed that the pistillate inflorescences were congested spikes with the flowers arrangedopposite.Great differences between the so-called"bract"and the vegetative leaf were observed both in morphogenesis andmorphology.In morphogenesis,the"bract"primordium is crescent-shaped,truncated at the apex and not conduplicate,has no stipule primordium at the base but does have some inconspicuous teeth in the margin that are not glandular.Theleaf primordium is triangular,cycloidal at the apex,conduplicate,has two stipule primordia at the base,has one gland-toothat the apex occurring at first and some gland-teeth in the margin that occur later.In morphology,the"bract"is also differentto the vegetative leaf in some characteristics that were also illustrated in the present paper.Based on the hypothesis thatthe bract is more similar to the vegetative leaf than the tepal,we considered that the so-called"bract"of C.japonicum mightbe the tepal of the pistillate flower in morphological nature.Therefore,each pistillate flower contains a tepal and a carpel.We did not find any trace of other floral organs in the morphogenesis of the pistillate flower.Therefore we consideredthat the unicarpellate status of extant Cercidiphyllum might be to highly reduce and advance characteristics that make theextant Cercidiphyllum isolated from both fossil Cercidiphyllum-like plants and its extant affinities.     

An improved Greengenes taxonomy with explicit ranks for ecological and evolutionary analyses of bacteria and archaea

Reference phylogenies are crucial for providing a taxonomic framework for interpretation of marker gene and metagenomic surveys, which continue to reveal novel species at a remarkable rate. Greengenes is a dedicated full-length 16S rRNA gene database that provides users with a curated taxonomy based on de novo tree inference. We developed a ‘taxonomy to tree'' approach for transferring group names from an existing taxonomy to a tree topology, and used it to apply the Greengenes, National Center for Biotechnology Information (NCBI) and cyanoDB (Cyanobacteria only) taxonomies to a de novo tree comprising 408 315 sequences. We also incorporated explicit rank information provided by the NCBI taxonomy to group names (by prefixing rank designations) for better user orientation and classification consistency. The resulting merged taxonomy improved the classification of 75% of the sequences by one or more ranks relative to the original NCBI taxonomy with the most pronounced improvements occurring in under-classified environmental sequences. We also assessed candidate phyla (divisions) currently defined by NCBI and present recommendations for consolidation of 34 redundantly named groups. All intermediate results from the pipeline, which includes tree inference, jackknifing and transfer of a donor taxonomy to a recipient tree (tax2tree) are available for download. The improved Greengenes taxonomy should provide important infrastructure for a wide range of megasequencing projects studying ecosystems on scales ranging from our own bodies (the Human Microbiome Project) to the entire planet (the Earth Microbiome Project). The implementation of the software can be obtained from http://sourceforge.net/projects/tax2tree/.     

Changing ideas about eukaryotic origins

The origin of eukaryotic cells is one of the most fascinating challenges in biology, and has inspired decades of controversy and debate. Recent work has led to major upheavals in our understanding of eukaryotic origins and has catalysed new debates about the roles of endosymbiosis and gene flow across the tree of life. Improved methods of phylogenetic analysis support scenarios in which the host cell for the mitochondrial endosymbiont was a member of the Archaea, and new technologies for sampling the genomes of environmental prokaryotes have allowed investigators to home in on closer relatives of founding symbiotic partners. The inference and interpretation of phylogenetic trees from genomic data remains at the centre of many of these debates, and there is increasing recognition that trees built using inadequate methods can prove misleading, whether describing the relationship of eukaryotes to other cells or the root of the universal tree. New statistical approaches show promise for addressing these questions but they come with their own computational challenges. The papers in this theme issue discuss recent progress on the origin of eukaryotic cells and genomes, highlight some of the ongoing debates, and suggest possible routes to future progress.     

Morphogenesis of Pistillate Flowers of Cercidiphyllum japonicum （Cercidiphyllaceae）

Floral morphogenesis and the development of Cercidiphyllumjaponicum Sieb. et Zucc. were observed by scanning electron microscopy （SEM）. The results showed that the pistillate inflorescences were congested spikes with the flowers arranged opposite. Great differences between the so-called ＂bract＂ and the vegetative leaf were observed both in morphogenesis and morphology. In morphogenesis, the ＂bract＂ primordium is crescent-shaped, truncated at the apex and not conduplicate, has no stipule primordium at the base but does have some inconspicuous teeth in the margin that are not glandular. The leaf primordium is triangular, cycloidal at the apex, conduplicate, has two stipule primordia at the base, has one gland-tooth at the apex occurring at first and some gland-teeth in the margin that occur later. In morphology, the ＂bract＂ is also different to the vegetative leaf in some characteristics that were also illustrated in the present paper. Based on the hypothesis that the bract is more similar to the vegetative leaf than the tepal, we considered that the so-called ＂bract＂ of C.japonicum might be the tepal of the pistillate flower in morphological nature. Therefore, each pistillate flower contains a tepal and a carpel. We did not find any trace of other floral organs in the morphogenesis of the pistillate flower. Therefore we considered that the unicarpellate status of extant Cercidiphyllum might be to highly reduce and advance characteristics that make the extant Cercidiphyllum isolated from both fossil Cercidiphyllum-like plants and its extant affinities.     

对翼蓼(蓼科)属级位置的重新探讨

通过对翼蓼Pteroxygonum giraldii Damm. &; Diels及相关属(蓼属Polygonum、何首乌属Fallopia、虎杖属Reynoutria、荞麦属Fagopyrum和金线草属Antenoron)的形态观察、果实解剖学观察、花被片脉序观察、花粉形态、核型分析, 以及ITS序列的分析确定了翼蓼和荞麦F. esculentum Moench较远的亲缘关系。其中我们发现翼蓼果实基部有三个角状物明显不同于其他属果实的形态特征。翼蓼外果皮明显加厚, 并有零星散布的波状内腔, 而荞麦的外果皮很薄, 细胞不等径, 中果皮极厚。以上证据证明了翼蓼与荞麦属亲缘关系较远。在观察荞麦属和翼蓼的花被片脉络时发现了两种不同的脉序类型, 符合将荞麦属分为两个组的划分。翼蓼花被片脉序为三出状, 支持将翼蓼归为Persicarieae族。对翼蓼及荞麦属植物的花粉进行比较后, 发现荞麦属植物的花粉网孔有明显的内凹穿孔而翼蓼却没有, 结果表明二者亲缘关系较远。通过对nrDNA ITS区域序列分析得出翼蓼及相关属为一个单系类群, 含有两个稳定的分支: 第一个分支由蓼属(萹蓄组sect. Avicularia)、何首乌属、虎杖属的植物组成, 第二个分支由蓼属(刺蓼组sect. Echinocaulon、蓼组sect. Polygonum、分叉蓼组sect. Aconogonon、拳参组sect. Bistorta、翼蓼和荞麦属植物组成。同时第二个分支又分成了两个亚分支, 蓼属(刺蓼组、蓼组、分叉蓼组、拳参组)和翼蓼属Pteroxygonum植物属于第一个亚支而荞麦属植物属于第二个亚支。结果支持翼蓼不属于荞麦属的范畴。实验结果显示翼蓼是个单型属, 属于Persicarieae族。     

Comparative anatomy and systematics of woody Saxifragaceae. Aphanopetalum Endl.

The floral and vegetative anatomy of the small Australian genus Aphanopetalum were studied. Wood is described for the first time and is characterized by predominantly solitary pores, scalariform vessel element perforation plates with low bar numbers, imperforate tracheary elements with distinctly bordered pits, sparse axial parenchyma, and a combination of homocellular and heterocellular rayS. Starch occurs in both axial and ray parenchyma of the wood. Stems possess unilacunar, one-trace nodes and the uncommon feature of an endodermis with well-defined Casparian stripS. Leaves have anomocytic stomata, a bifacial mesophyll and semicraspedodromous venation or a combination of semicraspedodromous and brochidodromous venation. The tetramerous flowers are apetalous or have minute petals. The compound, half-inferior gynoecium consists of essentially totally united carpels. The pattern of floral vascularization resembles different Saxifragaceae sensu lalo in that the compound sepal-plane and petal-plane traces give rise to staman bundles as well as sepal, petal, and carpel wall venation in their respective planes. The ventral ovarian bundles are fused into a single ventral complex that subdivides at the top of the ovary to form ventral bundles and to supply the one ovule in each locule. Vegetative and floral features provide compelling evidence to suggest that Aphanopetalum has its nearest relatives among the Saxifragaceae sensu lato rather than Cunoniaceae. The genus is probably best treated as forming its own subfamily (or family) among the saxifragaean alliance.     

Preliminary investigations of hybridization/reticulate evolution in Guaranidrilus (Enchytraeidae: Oligochaeta)

The identification of gut diverticula at 7/8 as a synapomorphy and recognition of all taxa of Guaranidrilus has been obscured by losses of gut diverticula within the lineage. The homoplastic occurrence of basally unpaired peptonephridia in some enchytraeid species has similarly obscured the limits of Hemienchytraeus. Taxa with unpredictable relationships, morphogenic irregularities in some reproductive structures, and, apparently, modified modes of reproduction, suggest the possibilities of hybridization between taxa with both close and distant relationships.     

低等六足动物系统学研究进展

低等六足动物包括原尾纲、弹尾纲和双尾纲三个类群,是探讨六足动物起源和进化问题的关键类群,近十年来成为节肢动物系统进化研究中的焦点之一。低等六足动物的系统发育地位以及它们之间的关系一直是备受争论的问题。通过介绍三类低等六足动物最新的分类系统,从经典分类学和系统发育两个方面对低等六足动物近十年来的研究进展进行了综述。迄今,对于三类低等六足动物都建立了比较完备的分类体系,原尾纲划分为3目10科,弹尾纲划分为4目30科,双尾纲划分为2亚目3总科10科。系统发育研究中,大多数的系统发育分析结果不支持传统的缺尾类假说,缺尾纲应摒弃不用。分子数据分析的结果普遍支持原尾纲与双尾纲近缘,但仍需要进一步探讨。线粒体基因组、比较胚胎学和比较精子学的研究结果表明,原尾纲可能经历了长期的趋异进化历史。最近的比较精子学研究支持了双尾纲的单系性。总之,三类低等六足动物系统学研究均取得了长足的发展,但仍然存在诸如研究人员匮乏和研究水平不均衡等问题。系统发育研究中,分子系统学研究成为关注的焦点,而基于核基因和线粒体基因的数据分别建立的系统发育假说存在分歧,亟需开发更优的数据分析方法。此外,需加强低等六足动物比较形态学、比较胚胎学、发育生物学等方面的研究,以便将来进行全证据的系统发育研究。     

Evolutionary approaches to cultural and linguistic diversity

Evolutionary approaches to cultural change are increasingly influential, and many scientists believe that a 'grand synthesis' is now in sight. The papers in this Theme Issue, which derives from a symposium held by the AHRC Centre for the Evolution of Cultural Diversity (University College London) in December 2008, focus on how the phylogenetic tree-building and network-based techniques used to estimate descent relationships in biology can be adapted to reconstruct cultural histories, where some degree of inter-societal diffusion will almost inevitably be superimposed on any deeper signal of a historical branching process. The disciplines represented include the three most purely 'cultural' fields from the four-field model of anthropology (cultural anthropology, archaeology and linguistic anthropology). In this short introduction, some context is provided from the history of anthropology, and key issues raised by the papers are highlighted.     

Leaf energy balance modelling as a tool to infer habitat preference in the early angiosperms

Despite more than a century of research, some key aspects of habitat preference and ecology of the earliest angiosperms remain poorly constrained. Proposed growth ecology has varied from opportunistic weedy species growing in full sun to slow-growing species limited to the shaded understorey of gymnosperm forests. Evidence suggests that the earliest angiosperms possessed low transpiration rates: gas exchange rates for extant basal angiosperms are low, as are the reconstructed gas exchange rates for the oldest known angiosperm leaf fossils. Leaves with low transpirational capacity are vulnerable to overheating in full sun, favouring the hypothesis that early angiosperms were limited to the shaded understorey. Here, modelled leaf temperatures are used to examine the thermal tolerance of some of the earliest angiosperms. Our results indicate that small leaf size could have mitigated the low transpirational cooling capacity of many early angiosperms, enabling many species to survive in full sun. We propose that during the earliest phases of the angiosperm leaf record, angiosperms may not have been limited to the understorey, and that some species were able to compete with ferns and gymnosperms in both shaded and sunny habitats, especially in the absence of competition from more rapidly growing and transpiring advanced lineages of angiosperms.     

广西黄皮属六种叶片的比较解剖观察

<正> 芸香科黄皮属(Clausena)植物全球约25种,分布于东半球热带、亚热带地区;我国记载有9种,产长江以南各省区,以两广、云南种类较多;广西现知6种,民间大多作药用,黄皮和小叶黄皮在我国南部广泛栽培,果实供生食或加工,黄皮的优良品种为岭南佳果之一。目前正在挖掘其潜在的药用价值及进行化学成分和挥发油的研究。中国人民解放军181医院药理室,用大鼠进行动物实验,证明黄皮叶有降血脂作用。在研究黄皮属的分类时,某些种的形态特征很接近,叶的形状、大小变化大,在无花果的情况下更难区分,笔者试图从叶的解剖构造探讨种间的差异,为植物分类和生药鉴定提供依据,供临床用药及有关方面参考。