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The genus Ottelia is one of the great genera of Hydrocharidaceae. About 25 species distributed in the Palaeotropics, extending from Africa through India and SE. Asia to Korea and Japan, Australia and New Caledonia, 1 species in Brazil; centres of specific devolopment are found in Central Africa and SE Asia. The present study is mainly based on the materials collected during the field explorations in the lakes of Yunnan and observations on the structure of the spathe and flowers, the variation of leaf of the plants cultivated in Kunming Bot. Garden. Instead of the wings of the spathe used by Dandy, by the characters such as uni-or bisexual flowers, this genus is divided into two subgenera, which by the number of the flowers in spathe and the number of the carpus in ovary again subdivided into 4 sections. They are as the following: A. Subg. Ottelia. Flowers bisexual. Sect. 1. Ottelia. Spathe with 1 flower; ovary with 6(—9) carpus. Sect. 2. Oligolobos (Gagnep.) Dandy. Spathe with many flowers; ovary with 3 carpus. B. Subg. Boottia (Wall.) Dandy. Flowers unisexual; the male spathe with 1-many flowers, the female spathe with many flowers. Sect. 3. Boottia. The male spathe with 1 flower; ovary with 9(—15) carpus. Sect. 4. Xystrolobos (Gagnep.) H. Li. The female spathe with (2-) many flowers; ovary with 3 or 9 carpus. The Chinense species of ottelia is in great need for revision. All of the species in China previousely described under Ottelia Pers, Boottia Wall., Oligolobos Gagnep, and Xystrolobos Gagen. are here combined into 3 species. They are O. alismoides, O. cordata, O. acuminata with 4 variaties. After a study of the geographic distribution and infer relation-ships among the floristic elements it has been proved that Ottelia is certainly an ancient genus, and the primitive types came into being and widely dispersed before the separation of Laurasia from Gondwana. During a considerable period of time the elements of the genus Ottelia in freshwater environment of different continents have been separately differentiated and evolved into more or less derived types. The structure of flowers in all of the asian species shows the following evolutionary tendenoes: 1. In this genus the plants with unisexual flowers have evolved from plants with bisexual flower; 2. In the groups with bisexual or unisexual flowers the number of stamens and styles reduced to 3-merous, but the number of flowers in spathe increased. So that the subgenus Ottelia is more primitive than the subgenus Bottia; While in the subgenus Ottelia O. alismoides is a more primitive than O. balansae and in the subgenus Boottia O. cordata is the most primitive, butO. alata seems to be the most advanced.  相似文献   

3.
柽柳科柽柳属的植物地理研究   总被引:8,自引:1,他引:7  
柽柳属是典型的旧世界温带分布属。对柽柳属3组68种的分布进行了分析,发现本属3个频度分布中心依次为伊朗—吐兰区的西亚亚区(30种/3组,其中特有种13种),中亚亚区(20种/2组,其中特有种6种)和地中海区(12种/3组,其中特有种6种)。由于伊朗—吐兰地区的西亚亚区存在本属最多的组与种、特有种多且可以见到柽柳属系统发育系列,因而认为该亚区是现存本属植物的现代分布中心和分化中心。地中海地区包含的组、种数仅次于伊朗—吐兰区,并且特有种为6种,带有新特有种的性质,全是系统发育上相对年轻、进步的类型,被认为是本属的一个次级分布中心,另一个次级分布中心在中亚亚区,尤其是中国西北干旱地区。根据柽柳属植物的现代地理分布、化石资料及地质历史资料,推测柽柳属起源于古地中海热带成分盛行的早第三纪始新世,具有起源古老的性质,并且随着晚第三纪古地中海的退缩、气候逐渐干旱而得到进一步发展,产生许多新的以温带成分为主适应旱生环境的现代柽柳属种类。柽柳属起源之后,首先繁衍、散布到以伊朗为中心的现代分布中心,其后以伊朗为廊道向西、向东扩散,在地中海沿岸、东非、阿拉伯半岛、非洲西南部及亚洲中部的荒漠地区得到发展。  相似文献   

4.
针对特有性简约性分析(PAE)不足之处,提出一个新的改进分析方法。主要区别是,新方法对分布区内分类群区分了原始和演化,相应地编码为0/1;为了获取分类群原始和演化的特性,分析以分类群分支图为基础。新方法是系统发育与地理分布相统一原理的一个具体的定量化探讨。用新方法分析了豆科锦鸡儿属锦鸡儿组15种,结果表明新方法优于以前的PAE方法。用新的改进方法分析得到的可能的祖先分布区是原始类群树锦鸡儿和一大类属内原始类群的分布区。与目前属的起源问题的一般观点相一致。  相似文献   

5.
王文采   《广西植物》1995,15(2):189-192
(1)在各种花对称的分类中,Ehrendorfer的分类包括了被子植物花对称方面从原始到进化的各种类型,最为全面广德国学者Strasburer在1911年编著的第11版植物学教科书中将具2对称面的荷包牡丹属的花称为bilateral或disymmetrisch.这个类型代表了被子植物花的一种较进化的构造,应该予以肯定。由于被指定为描述具2对称面的花的术语bilateral与被指定为描述具丑对称面的花的术语bilaterallysymmetrical颇为相似,而易引起混淆.为避兔发生混淆.建议不再应用这二术语.在描述具2对称面的花时,选用disymmetrical,中文译为双面对称的,在描述具1对称面的花时,选用zygomorphic(左右对称的)或monosymmetrical,后者的中文可译为单面对称的。(2)赞同将术语tepal译为花被片,而不赞同译为“被片”。  相似文献   

6.
绞股蓝属植物的分类系统和分布   总被引:34,自引:0,他引:34  
绞股蓝属全世界有16种2变种,隶属于2亚属2组,即喙果藤亚属(包括五柱绞股蓝组和喙果藤组)及绞股蓝亚属。其现代分布中心或多样化中心为我国长江流域至西南的云南,由此向北达秦岭南坡和淮河流域以南,向东北经华中、华东至朝鲜半岛和日本北部,向南经中南半岛、马来西亚达菲律宾、印度尼西亚诸岛和巴布亚新几内亚,向西达印度西北部,为热带亚洲分布类型。根据该属的原始类群和进化类型的现代分布和多样化中心及它们的生态适应性,与古地质、古地理和古气候的变迁以及外类群起源地等推测,绞股蓝属植物可能与其近缘属——雪胆属和锥形果属共同起源于康滇古陆,起源时间可能为早第三纪。  相似文献   

7.
The genus Gynostemma consists of 16 species and 2 varieties, which fall into two subgenera and two sections, i. e. , Subgen. Trirostellum including two new sections, Sect. Pentagynae and Sect. Trirostellae, and Subgen. Gynostemma. The modern distribution centre of the genus ranges from drainage areas of the Yangtze River to Yunnan, southwest China. Northwards, it is distributed to the south slope of the Qinling Range and the south branch of the Huaihe River, eastwards through central-eastern China to Korea Peninsula and northern Japan; in the south, it extends to Indo-China, Malaysia, Philippines, Indonesia and Papua New Guinea, with the west limit of this genus found in northwestern India.The distribution pattern of the genus indicates a nature of Tropical Asia Type. Based on the above mentioned distribution pattern, the centre of diversification and the ecological adaptation of both primitive and advanced groups, also by means of palaeogeological, palaeogeographical and palaeoclimatical evidence and the origin of its out group, the genus Gynostemma, together with its closely allied genera Hemsleya, Gomphogyne, etc. is considered to have originated on the Kham-Dian Oldland during the Early Tertiary.  相似文献   

8.
A large sample of skulls and associated dentitions of Cormohipparion sphenodus (Cope, 1889). new combination, is described from Miocene deposits of Nebraska, Colorado, New Mexico, and California. This species is morphologically more advanced than the most primitive species of the genus, C. goorisiMacFadden & Skinner, 1981, and more primitive than a third and more advanced species of this genus. C. occidentale (Leidy, 1856). In several characters such as configuration of the preobrital fossa, size, hypsodonty, shape of protocone, and complexity of enamel plication, C. sphenodus is morphologically similar, and potentially related to, some Old World Vallesian «Hipparion. In addition, based on radiometric calibration of stratigraphic sequences in Nebraska and California, C. sphenodus spans an interval of time from about 13.6 to 11 Ma. Inasmuch as the Old World «Hipparion Datum is calibrated at about 12 Ma, we conclude that C. sphenodus exhibits the morphological and chronological prerequisites to have been directly ancestral to some of these Old World forms.The hipparion horses apparently were a polyphyletic assemblage of several genera, and their biogeographic and biochronologic history is more complex than classically thought. Several dispersal events involving these horses may have occurred between the New and Old Worlds during the late Miocene.  相似文献   

9.
根据叶表皮特征试论国产三齿稃亚族的属间关系   总被引:4,自引:3,他引:1  
根据植物叶片表皮结构,尤其下表皮特征,对国产三齿稃亚族6个属(包括1个引进属)进行了属间关系的分析。结果表明:国产三齿稃亚族中固沙草属最原始,草沙蚕属最高级,双稃草属、千金子属、三齿稃属和隐子草属演化居于其间;隐子草属可能直接起源于固沙草属,并在自身基础上派生了较为高级的三齿稃属;双稃草属与千金子属渊源关系直接,前者可能通过后者问接起生于固沙草属;草沙蚕属具有别于它属的性状级次,可能是起源于固沙草属、独树1支的顶级类群。这一结果不仅修正了前人演化理论的差误,而且为今后探讨该亚族的地理起源、散布路线提供了资料。  相似文献   

10.
M Shimizu 《Origins of life》1984,14(1-4):531-538
The role of "theoretical physics" in the elucidation of the origin of life has been advanced by Eigen's hypercycle theory on ancient protein synthesis system and by Dyson's random drift theory on the autocatalytic formation of enzymes, although these approaches from the informational side involve many problems to be resolved. On the other hand, our C4N model calls for a stronger role of physico-chemistry in the understanding of the origin of life. Plant virus and movable genes could be the fossil vestiges of the ancient protein synthetic system, where tRNA identical to mRNA identical to gene. It is pointed out that functional differentiation of proteins closely correlates with the structure of the primitive tRNAs. Possible initial forms of the primitive tRNAs used by the earliest organisms are explicitly shown, in which the above correlation is carefully taken into account. The system of the primitive genes and the primitive enzymes in the proto-cellular membrane, say the marigranule, might simulate the earliest organism.  相似文献   

11.
3属3种毛茛科植物幼苗形态结构及其系统演化分析   总被引:1,自引:0,他引:1  
梁彦  汪矛  郭洁  周树敏  王丽 《西北植物学报》2007,27(7):1357-1363
以毛茛科升麻属植物升麻(Cimicifuga foetida)、金莲花属植物短瓣金莲花(Trollius ledebouri)和飞燕草属植物飞燕草(Consolida ajacis)为材料,应用整体透明和石蜡连续切片方法,对3种植物幼苗形态特征及初生维管系统结构进行了观察。结果表明:升麻子叶脉序为较简单的离基不完全顶聚脉,短瓣金莲花为环结曲行羽状脉,飞燕草为较复杂的基出完全顶聚脉。升麻属幼苗子叶节区下部的维管柱为中始式二原型长方形单中柱,金莲花属为外始式二原型半弧形单中柱,飞燕草属为外始式二原型双扇形单中柱。分析上述子叶脉序特征和维管柱类型,认为3属中升麻属最原始,金莲花属次之,飞燕草属进化程度最高。  相似文献   

12.
Summary The components of variation within each one of two sets of landraces and/or cultivars of Vicia faba, respectively constituted of primitive and advanced morphological types, were studied by means of two sets of 8 × 8 diallel crosses with two repetitions. The results show that primitive and modern forms differ from each other in both the intensity and the kind of selective pressures acting on them, mainly on those characters more modified through the domestication process: i.e., seed morphology and the number of flowers per node. Because of the paramount importance of the additive component in the primitive forms, it is suggested that the most important type of selection on them is the stabilizing one. On the contrary, in the most advanced forms the selection is directional and disruptive : directional towards greater yields, and disruptive separating two morphological types, major and equina. The plant response to these different selective pressures has been to modify the genetic control of different characters: thus the primitive forms generally show only additivity while the most advanced forms show additivity as well as directional and asymmetrical dominance.  相似文献   

13.
This paper is an attempt to discuss the relationship and phylogeny within the genus Lindera, based upon on analysis of shortened brachlets, on which the inflorescences are inserted, and other morphological characters. The shortened branchlets are metamorphic shoots which are often at the transitional stage between branchles and inflorescences. The advanced shortened branchlets usually with an undeveloped terminal bud, posses scale-like leaves, and the inflorescences so formed are sessile and aggregate. In primitive taxa, such as Lindera nacusua (Don) Merr., L. gracilipes H. W. Li and L. tanchuanensis Feng et H. S. Kung, the branchlet is usually not shortened, with well-developed terminal bud, forming a single axillary pseudo-umbel, while its peducle is usually very slender and stamens of pistillate flower sometimes more or less developed. The leaves on the upper part of branchlet are normal and the lower part of branchlet becoming bracteal, In the genus the development of shortened branchlets (Fig. 1.) from the ones in the primitive taxa to the ones in the advanced taxa may be found. Other important morphological characters are the length of peducles. The peduncle is usually slender in the primitive taxa, short or even sessile in the adanced taxa. There are two types of venation in the genus: the pinnate and trinerved. As the primitive group trib. Perseeae Mez shows pinnate veins, pinnate ventation in Lindera is more primitive than trinerved one. It might be possible that a transition occure in the genus from evergereen habit to deciduous one as shown in Lindera glauca B1., L. angustifolia Cheng and L. praecox B1., whose leaves tardily wither but persistent over winter. The relationships within Lindera are shown in a hypothetical genealogical tree (Fig. 4), which includes the system of Litsea, developed parallelly with Lindera. From the study of morphological characters, the author infers that both Lindera and Litsea have originated from a common ancestory related to the tribe Cinnamomeae Baill. which has a single axillary inflorescence, with hermaphrodite flowers, 4-locular anthers and penninerved to trinerved leaves.  相似文献   

14.
The middle ear regions of reptiles and amphibians frequentlyare grouped into morphological types on the basis of structuralresemblances. The arrays of animals resulting from such a groupinghave a fair degree of taxonomic continuity. The types in mostinstances include a "central" pattern, presumed to be primitive,and modifications that are considered to have been derived fromthe "central" type by evolutionary processes. Some understandingof phylogeny, thus, is a necessary precursor to the formationof the groups. This raises problems when, as is often the case,the groups based on ear structures are used as a basis for phylogeneticinterpretations. Among reptiles the theropsid-sauropsid caseis the best known. The principal morphological types are described and discussed.The middle ear, as a sound-transmitting apparatus and in itsassociations with the masticatory apparatus, is highly susceptibleto adaptive modifications. Some morphological types, such asthose in archosaurs and labyrinthodonts, are quite stable. Othersshow marked evolutionary diversity. The middle ear structures,hence, appear quite useful as phylogenetic indicators withinmorphological types but less so when relationships between typesare considered.  相似文献   

15.
通过国产画眉草亚族叶片表皮的解剖观察,结合外部形态,对该亚族内6个属的属间关系进行了分析。结果表明:羽穗草属应是国产画眉草亚族中最原始的类群,最高级的类群仍数细画眉草属,而其余4属即画眉草属、弯穗草属、尖稃草属和镰稃草属的演化水平居于两者之间;画眉草属和弯穗草属可能直接起源于原始的羽穗草属,而较高级的尖稃草属和镰稃草属又可能直接起源于较原始的画眉草属,并在镰稃草属的基础上进而派生了最进化的细画眉草属。整个研究结果既弥补了前人演化理论的不足,又为今后族进化的全面探讨提供了参考。  相似文献   

16.
SYNOPSIS. Major events in the history of the blood O2 carriersin multicellular animals include: 1) The origin of the red bloodcell hemoglobins, which are both the most primitive and themost advanced O2 carriers. At the molecular level, they arebelieved to have arisen only once; at the animal level, thereis no cogent reason to postulate more than two origins. 2) Theorigin of the hemerythrins, which occur at about the same phylogeneticlevel as the primitive red blood cell hemoglobins. They maynot have been selected in higher animals because of their temperaturesensitivity. The origins of 3) the molluscan hemocyanins and4) the arthropod hemocyanins. These two events occurred independently,though for similar reasons. Both kinds of hemocyanins offeredphysiological advantages over the primitive hemoglobins thatwere important in the context of the more advanced molluscanand arthropod cardiovascular systems. 5) The origins of extracellularheme proteins, which arose independently many tunes, and probablyfor as many different reasons. 6) The loss of urea sensitivity,and the acquisition of organic Po4 sensitivity and additionalcooperativity and pH dependence by the red blood cell hemoglobins,which occurred well after the origin of the vertebrates.  相似文献   

17.
The acquisition of intracellular organelles, including mitochondria and plastids and a membrane-bounded nucleus, have been postulated to be key events in the development of the eukaryotic from the prokaryotic ancestral cell. The two major hypotheses to account for such acquisitions are: (1) primitive cells originally obtained organelles by engulfing free-living prokaryotes which then entered into symbiotic association (“endosymbiosis”) with them; (2) organelles arose through the engulfment by the primitive cell of part of its own cytoplasm. To some extent, the former hypothesis has received most support, because endosymbiosis is known to occur in extant organisms, whilst the latter hypothesis has received less support, because cytoplasmic engulfment by prokaryotes is not now thought to occur. However, during the process of endospore formation by extant bacteria, the protoplast within the single cell is observed to divide in a unique manner such that the cell in effect engulfs a portion of its own cytoplasm. The process is strikingly similar to the engulfment suggested by the second hypothesis to have initiated the evolution of eukaryotes. The engulfed cytoplasm is bounded by a double membrane within the “mother cell” and contains enzymes, ribosomes and a complete genome. In many respects this parallels the supposed primitive eukaryotic state and, it is argued, confers potential advantages on the cell, particularly through the control that the “mother cell” can exert on the enclosed compartment. It is hypothesized that bacterial endospore formation is therefore one product of evolution from an early engulfment event that led also to the development of complex eukaryotic cells.  相似文献   

18.
19.
Wittzell H 《Molecular ecology》1999,8(12):2023-2035
Sequencing of the trnL-trnF intergenic spacer in chloroplast DNA (cpDNA) from 237 sexual and apomictic species of dandelions (genus Taraxacum) from Europe, Asia and arctic North America revealed 46 haplotypes, which differed mainly by a variable number of polymorphic tRNA pseudogenes next to the trnF gene. The haplotypes could be divided into 20 cpDNA lineages, but independent duplications and deletions of the pseudogene copies made it difficult to further reconstruct the phylogeny. Intraspecific cpDNA variation was found in the primitive sexual T. serotinum. However, in contrast to a recent study, no cpDNA variation was detected within 12 apomictic species representing a variety of haplotypes. The cpDNA haplotype may therefore help to define these critical apomicts. On the other hand, the genetic variation may easily be overestimated, if the clones are not correctly identified, because some morphologically similar microspecies carried very different haplotypes. In all, 36 sections of the genus were sampled. Four primitive, mainly sexual, sections only displayed a group of ancient haplotypes, whereas morphologically more advanced sections often exhibited many different haplotypes from up to seven cpDNA lineages. In the latter cases, the lineages were rarely unique to a certain section. For example, the two most widespread haplotypes, belonging to different lineages, were found together in nine sections. This suggests that significant gene flow has occurred among the advanced sections, although sexual reproduction is not currently known in several of them. The result is consistent with the reticulate distribution of morphological characters among the sections.  相似文献   

20.
中国杜鹃花属高山杜鹃亚组的数量分类研究   总被引:5,自引:1,他引:4  
本文是一篇关于杜鹃花属高山杜鹃亚组数量分类的文章,记录了一个具有45个OTU's×46个性状的原始数值矩阵。对性状标准化以后,计算相关矩阵和距离矩阵,这些矩阵作为每一对OTU's之间的相似性定量的表示。然后在这些矩阵上计算各种方法的聚类,有单联、全联、UPGMA,WPGMA,重心,中线等等。以综合比较系数(见表 3)作为好的分类判别标准,最后选取相关系数矩阵作为运算结果。(见图)展示出WPGMA的树系图。Ⅰ.树系图所显示的结果有助于揭示类群的分类和演化规律:高山杜鹃亚组应分为两群,即高山群和坚挺群。  相似文献   

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