金鱼藻科系统位置评述

金鱼藻科(ceratophyllaceae)含1属7种,广布全世界。形态学研究显示,金鱼藻科具有许多难以解释的性状,与其它类群无法比较;最新的分子系统发育研究显示,金鱼藻科是现存被子植物的基部类群之一;有关金鱼藻科的系统位置存在争议,被子植物(有花植物)的起源与辐射一直是植物系统学家关注的热点。本文对该科系统位置的研究历史与现状进行评述。     

互叶梅科系统位置评述

互叶梅科(Amborellaceae)一属一种。形态学研究显示互叶梅(Amborella,tricopoda Baill．)具有许多原始性状。大多数最新的分子系统发育研究显示,互叶梅科是现存被子植物的最基部类群。但有关互叶梅科的系统位置存在争议。被子植物(有花植物)的起源和辐射一直是植物学家关注的热点。本文将对该科系统位置的研究历史与现状进行评述。     

莲科系统位置评述

莲科含1属1种2亚种,以具有最古老的有活力的种子而著称。形态学研究显示,莲不仅具有双子叶植物特征,而且又具有单子叶植物的某些性状。因此,对研究被子植物(有花植物)的起源与演化以及单子叶植物的起源具有重要价值。被子植物(有花植物)的起源与辐射一直是植物学家关注的热点,有关莲科的系统位置存在争议。该文对该科系统位置的研究历史与现状进行评述。     

木兰藤科系统位置评述

木兰藤科(Austrobaileyaceae)含1属2种,是系统学上最孤立的科之一。其花粉类似于最古老的被子植物化石之一:晚白垩世的棒纹粉。最新的分子系统发育研究结果表明,木兰藤科是现存被子植物的基部类群之一,其对于被子植物的起源与早期进化的研究具有重要价值。被子植物(有花植物)的起源和辐射一直是植物学家关注的热点。有关木兰藤科的系统位置一直存在争议。本文对该科系统位置的研究历史与现状进行评述。     

互叶梅科系统位置评述

互叶梅科 Amborellaceae 一属一种 .形态学研究显示互叶梅 Amborella tricopoda Baill. 具有许多原始性状 .大多数最新的分子系统发育研究显示 ,互叶梅科是现存被子植物的最基部类群 .但有关互叶梅科的系统位置存在争议 .被子植物 有花植物 的起源和辐射一直是植物学家关注的热点 .本文将对该科系统位置的研究历史与现状进行评述     

睡莲科系统位置评述

形态学研究显示睡莲科Nymphaeaceae具有许多原始性状。睡莲科又被称为“古草本”。最新的分子系统发育研究显示,睡莲科是现存被子植物系统树根部附近最早分异谱系的演化支之一,对研究被子植物(有花植物)的起源与早期进化具有重要价值,但有关睡莲科的范围和系统位置存在争议。被子植物的起源与辐射一直是植物学家关注的热点。本文对该科系统位置的研究历史与现状进行了评述。     

几个被子植物基部类群简介

被子植物系统学研究取得重要新进展，确定了几个被子植物基部类群。介绍了其中仅分布于南半球西太平洋地区的互叶梅属、腺齿木属和对叶藤属的形态特点。     

水盾草科系统位置评述

水盾草科(Cabombaceae)是双子叶植物。水盾草科包括2属: 水盾草属(Cabomba Aublet.)和莼菜属(Brasenia Schreb.)。形态学研究显示水盾草科具有许多原始性状, 而且在其适应水生环境的过程中经历了性状退化。水盾草科又被称为“古草本”。最新的分子系统发育研究显示, 水盾草科是现存被子植物系统树基部ANITA类群的成员之一。但有关水盾草科的系统位置存在争议。被子植物的起源与早期分化一直是植物学家关注的热点。本文对该科系统位置的研究历史与现状进行评述。     

被子植物APG分类系统评论

随着植物分子系统学的兴起,被子植物系统发育研究取得了举世瞩目的进展。被子植物系统发育组提出了基于DNA证据的被子植物在目、科分类阶元上的分类系统,简称APG系统。本文简要概括了APG系统的主要成就:(1)验证了被子植物分类系统的可重复性和可预言性;(2)解决了一些依据形态学性状未能确定的类群的系统位置;(3)证明了将被子植物一级分类分为双子叶植物和单子叶植物的不自然性;(4)证实了单沟花粉和三沟花粉在被子植物高级分类单元划分中的重要性;(5)发现雄蕊的向心发育和离心发育在多雄蕊类群中是多次发生的,不应作为划分纲或亚纲的重要依据;(6)支持基于形态学(广义)性状划分的大多数科是自然的;(7)将一些长期认为自然的科四分五裂。同时,我们指出了尚需深入研究的几个问题:(1)如何将以分子数据建立的系统和以综合形态学证据建立的系统相协调;(2)依据APG系统的研究结果需要创立新的形态演化理论;(3)只以"单系群"作为划分科、目的依据值得商榷;(4)APG系统中一些目的分类没有可信的形态学共衍征;(5)依据APG系统需要做出一个自然系统的目、科检索表和目、科的特征集要。此外,我们对以亚洲,特别是东亚为分布中心的一些类群的系统关系或分类等级提出建议,包括八角科、芒苞草科、水青树科、火筒树科、马尾树科、七叶树科、槭树科、伯乐树科应独立为科,山茱萸科(广义)应分为山茱萸科(狭义)和蓝果树科(广义)。     

被子植物雌全同株性系统:系统演化、性表达与进化意义

雌全同株是指雌花和两性花共同发生在同一植株上的性表达形式。作为被子植物从雌雄同花(两性花)向雌雄同株异花进化的一个重要阶段,雌全同株性系统在减少昆虫对雌性的取食和伤害、提高异交率以减少近交衰退、减少雌/雄功能干扰、提高雌/雄性功能间资源分配的灵活性,以及吸引传粉者等方面具有重要的进化适应意义。根据APG III分类系统,雌全同株性系统在被子植物木兰分支(magnoliids)的短蕊花科、单子叶植物分支(monocots)的天南星科和禾本科,以及核心真双子叶植物分支(core eudicots)中的菊科、苋科、唇形科和石竹科等23科中均有报道,且以菊科植物中最多。雌全同株植物不同类群的雌花和两性花在位置、形态、大小及开花时间等性表达特征上表现出多样化,且这些特征不仅受遗传因子的调控,还受可获得资源(如营养、光照、温度和水分等条件)的制约。该文针对我国对雌全同株性系统的研究还相对较少的现状,重点对具雌全同株性系统的类群在被子植物中的分布与系统演化、性表达与环境的关系等方面进行了分析与总结,并对有关其进化适应意义的5个假说进行了介绍和评价,对今后的研究方向进行了展望,以期为推动我国对被子植物雌全同株性系统的进化式样与机制研究提供理论资料。     

PhyloSort: a user-friendly phylogenetic sorting tool and its application to estimating the cyanobacterial contribution to the nuclear genome of Chlamydomonas

Background

Molecular phylogenetic analyses have identified Trimeniaceae, a monotypic family distributed only in Oceania, as among the earliest diverging families of extant angiosperms. Therefore, the fossils of this family are helpful to understand the earliest flowering plants. Paleobotanical information is also important to track the historical and geographical pathways to endemism of the Trimeniaceae. However, fossils of the family were previously unknown from the Early Cretaceous, the time when the angiosperm radiated. In this study, we report a seed from the late Albian (ca. 100 million years ago) of Japan representing the oldest known occurrence of Trimeniaceae and discuss the character evolution and biogeography of this family.

Results

A structurally preserved seed was collected from the early Late Albian Hikagenosawa Formation of the Yezo Group, which was deposited in palaeolatitudes of 35 to 40°N. The seed has a multilayered stony exotesta with alveolate surface, parenchymatous mesotesta, and operculate inner integument, which are characteristic to extant trimeniaceous seeds. However, the seed differs from extant seeds, i.e., in its well-developed endosperm and absence of antiraphal vascular bundle. Thus, the seed would be a new genus and species of Trimeniaceae.

Conclusion

The fossil seed indicates that seed coat characters were conserved for 100 million years or more in Trimeniaceae. It also suggests that the antiraphal vascular bundle and perispermy originated secondarily in Trimeniaceae as previously inferred from the phylogeny and character distribution in the extant basalmost angiosperms. The fossil seed provides the first evidence that Trimeniaceae was distributed in a midlatitude location of the Northern Hemisphere during the Early Cretaceous, when angiosperms radiated extensively, supporting a hypothesis that the extant austral distribution is relict.     

DNA C-values in seven families fill phylogenetic gaps in the basal angiosperms

The evolutionary significance of the c . 1000-fold range of DNA C-values in angiosperms (1C =  c . 0.1–127.4 pg) has often attracted interest. A recent analysis, which superimposed available C-value data onto the angiosperm phylogeny, that placed Ceratophyllaceae as the most basal angiosperm family led to the conclusion that ancestral angiosperms were characterized by small genomes (defined as 1C £ 3.5 pg). However, with the recent increase in DNA sequence data and large-scale phylogenetic analyses, strong support is now provided for Amborellaceae and/or Nymphaeaceae as the most basal angiosperm families, followed by Austrobaileyales (comprising Schisandraceae, Trimeniaceae and Austrobaileyaceae). Together these five families comprise the ANITA grade. The remaining basal angiosperm families (Ceratophyllaceae, Chloranthaceae and magnoliids), together with monocotyledons and eudicotyledons, form a strongly supported clade. A survey showed that C-value data were scarce in the basal angiosperm families, especially the ANITA grade. The present paper addresses these phylogenetic gaps by providing C-value estimates for each family in ANITA, together with C-values for species in Chloranthaceae, Ceratophyllaceae and a previously unrepresented family in the magnoliids, the Winteraceae.  © The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 175–179.     

Development and structure of the female gametophyte in <Emphasis Type="Italic">Austrobaileya scandens</Emphasis> (Austrobaileyaceae)

Austrobaileyales, comprising the four families Austrobaileyaceae, Trimeniaceae, Schisandraceae, and Illiciaceae, are included in the basal angiosperms along with Amborellaceae and Nymphaeaceae. Here, we present the first developmental study of the female gametophyte in Austrobaileya scandens, the only species of Austrobaileyaceae, which are sister to the rest of the Austrobaileyales. Austrobaileya scandens has a four-celled/four-nucleate embryo sac as in the derived families of the order, e.g., Illiciaceae and Schisandraceae. It is monosporic, with the chalazal megaspore of a tetrad developing into the embryo sac composed of an egg cell, two synergids, and one polar nucleus. This mode of embryo sac formation was first reported in Schisandra over 40 years ago and should now be established as the Schisandra type. Its occurrence in A. scandens shows that the Schisandra-type embryo sac is likely common to the whole Austrobaileyales as well as to Nymphaeaceae. Amborellaceae were recently reported to have an eight-celled/nine-nucleate embryo sac, clarifying that none of the basal angiosperms has the seven-celled/eight-nucleate Polygonum-type embryo sac found in the majority of angiosperms, and that the Polygonum-type embryo sac represents a derived character state in angiosperms.     

Variation and similarities in pollen features in some basal angiosperms, with some taxonomic implications

Species within three families of basal angiosperms (Trimeniaceae, Winteraceae, Monimiaceae) illustrate differences and similarities in pollen within a species, between species and between genera. Trimenia papuana (Trimeniaceae) has dimorphic pollen (inaperturate, polyforate), each confined to different individual plants. Other species have either disulculate or polyforate pollen. Evolution seems to be from disulculate to inaperturate to polyforate. Present-day Winteraceae have pollen in permanent tetrads except four species of Zygogynum with monads. Why? Did such monads appear as fossils before tetrads in Winteraceae? Molecular studies of Takhtajania perrieri indicate it is basal but its unique bicarpellate unilocular gynoecium seems derived. Although Hedycarya arborea and Kibaropsis caledonica have near-identical permanent pollen tetrads, many other features are very different. Hedycarya species have permanent tetrads or inaperturate monads with spinulose, `starry' or other sculpturing, and it is suggested this and recent molecular data indicate further studies are needed to determine generic limits.     

Erratum

It is confirmed for Piptocalyx moorei Oliver of the Lauralean family Trimeniaceae, from an examination of the shape of immature pollen at the tetrad stage and soon afterwards, that its biaperturate pollen is of the disulculate type. Two elongated apertures are latitudinally aligned at the equator of each grain.     

The exine ultrastructure of pollen grains in Gnetum (Gnetaceae) from China and its bearing on the relationship with the ANITA Group

Pollen grains of six species of Gnetum , G. parvifolium , G. hainanense , G. luofuense , G. pendulum , G. cleistostachyum and G. montanum , collected from China were examined using light, scanning and transmission electron microscopy. Pollen grains of Gnetum are subspheroidal or irregular-apolar, inaperturate, 11.21–22.44 µm in long axis and 9.34–20.47 µm in short axis. The exine surface is covered with spinules, 0.50(0.30–0.71) µm long spaced on average 1.12(0.81–1.46) µm apart. The exine is about 0.55 µm thick and comprises ectexine and endexine. The ectexine includes a thin tectum and an infratectal granular layer. The tectum protrudes outwards, forming the spinules. The endexine is composed of discontinuous lamellae, with lacunae between lamellae. The pollen grains of Gnetum are compared with those of Ephedra and Welwitschia , and also those of the ANITA Group of angiosperms, including Amborellaceae, Nymphaeales, Illiciales, Trimeniaceae and Austrobaileyaceae. The exine ultrastructures of Gnetum , Ephedra and Welwitschia are quite similar, consisting of tectum, granular layer and lamellated endexine. The exine ultrastructure of Gnetum is also similar to that of Nymphaea colorata (Nymphaeaceae) in the transitional region between the proximal and distal poles, but differs from that of Amborellaceae, Illicium religiosum (Illiciaceae), Schisandra (Schisandraceae), Trimeniaceae and Austrobaileyaceae. This comparison of exine ultrastructure provides new evidence for consideration of the relationship between Gnetum and the ANITA Group.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 415–425.     

Perspective: the origin of flowering plants and their reproductive biology--a tale of two phylogenies

Recently, two areas of plant phylogeny have developed in ways that could not have been anticipated, even a few years ago. Among extant seed plants, new phylogenetic hypotheses suggest that Gnetales, a group of nonflowering seed plants widely hypothesized to be the closest extant relatives of angiosperms, may be less closely related to angiosperms than was believed. In addition, recent phylogenetic analyses of angiosperms have, for the first time, clearly identified the earliest lineages of flowering plants: Amborella, Nymphaeales, and a clade that includes Illiciales/ Trimeniaceae/Austrobaileyaceae. Together, the new seed plant and angiosperm phylogenetic hypotheses have major implications for interpretation of homology and character evolution associated with the origin and early history of flowering plants. As an example of the complex and often unpredictable interplay of phylogenetic and comparative biology, we analyze the evolution of double fertilization, a process that forms a diploid embryo and a triploid endosperm, the embryo-nourishing tissue unique to flowering plants. We demonstrate how the new phylogenetic hypotheses for seed plants and angiosperms can significantly alter previous interpretations of evolutionary homology and firmly entrenched assumptions about what is synapomorphic of flowering plants. In the case of endosperm, a solution to the century-old question of its potential homology with an embryo or a female gametophyte (the haploid egg-producing generation within the life cycle of a seed plant) remains complex and elusive. Too little is known of the comparative reproductive biology of extant nonflowering seed plants (Gnetales, conifers, cycads, and Ginkgo) to analyze definitively the potential homology of endosperm with antecedent structures. Remarkably, the new angiosperm phylogenies reveal that a second fertilization event to yield a biparental endosperm, long assumed to be an important synapomorphy of flowering plants, cannot be conclusively resolved as ancestral for flowering plants. Although substantive progress has been made in the analysis of phylogenetic relationships of seed plants and angiosperms, these efforts have not been matched by comparable levels of activity in comparative biology. The consequence of inadequate comparative biological information in an age of phylogenetic biology is a severe limitation on the potential to reconstruct key evolutionary historical events.     

Was the ANITA rooting of the angiosperm phylogeny affected by long-branch attraction? Amborella, Nymphaeales, Illiciales, Trimeniaceae, and Austrobaileya

Five groups of basal angiosperms, Amborella, Nymphaeales, Illiciales, Trimeniaceae, and Austrobaileya (ANITA), were identified in several recent studies as representing a series of the earliest-diverging lineages of the angiosperm phylogeny. All of these studies except one employed a multigene analysis approach and used gymnosperms as the outgroup to determine the ingroup topology. The high level of divergence between gymnosperms and angiosperms, however, has long been implicated in the difficulty of reconstructing relationships at the base of angiosperm phylogeny using DNA sequences, for fear of long-branch attraction (LBA). In this study, we replaced the gymnosperm sequences from the five-gene matrix (mitochondrial atp1 and matR, plastid atpB and rbcL, and nuclear 18S rDNA) used in our earlier study with four categories of divergent sequences--random sequences with equal base frequencies or equally AT- and GC-rich contents, homopolymers and heteropolymers, misaligned gymnosperm sequences, and aligned lycopod and bryophyte sequences--to evaluate whether the gymnosperms were an appropriate outgroup to angiosperms in our earlier study that identified the ANITA rooting. All 24 analyses performed rooted the angiosperm phylogeny at either Acorus or Alisma (or Alisma-Triglochin-Potamogeton in one case due to use of a slightly different alignment) and placed the monocots as a basal grade, producing genuine LBA results. These analyses demonstrate that the identification of ANITA as the basalmost extant angiosperms was based on historical signals preserved in the gymnosperm sequences and that the gymnosperms were an appropriate outgroup with which to root the angiosperm phylogeny in the multigene sequence analysis. This strategy of evaluating the appropriateness of an outgroup using artificial sequences and a series of outgroups with increments of divergence levels can be applied to investigations of phylogenetic patterns at the bases of other major clades, such as land plants, animals, and eukaryotes.     

轮藻和陆地植物系统发育及其进化

Charophytic algae and land plants together make up a monophyletic group, streptophytes, which represents one of the main lineages of multicellular eukaryotes and has contributed greatly to the change of the environment on earth in the Phanerozoic Eon. Significant progress has been made to understand phylogenetic relationships among members of this group by phylogenetic studies of morphological and molecular data over the last twenty-five years. Mesostigma viride is now regarded as among the earliest diverging unicellular organisms in streptophytes. Characeae are the sister group to land plants. Liverworts represent the first diverging lineage of land plants. Hornworts and lycophytes are extant representatives of bryophytes and vascular plants, respectively, when early land plants changed from gametophyte to sporophyte as the dominant generation in the life cycle. Equisetum, Psilotaceae, and ferns constitute the monophyletic group of monilophytes, which are sister to seed plants. Gnetales are related to conifers, not to angiosperms as previously thought. Amborella, Nymphaeales, Hydatellaceae, Illiciales, Trimeniaceae, and Austrobaileya represent the earliest diverging lineages of extant angiosperms. These phylogenetic results, together with recent progress on elucidating genetic and developmental aspects of the plant life cycle, multicellularity, and gravitropism, will facilitate evolutionary developmental studies of these key traits, which will help us to gain mechanistic understanding on how plants adapted to environmental challenges when they colonized the land during one of the major transitions in evolution of life.