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1.
Cladistic analysis of nuclear-encoded rRNA sequence data provided us with the basis for some new hypotheses of relationships within the green algal class Ulvophyceae. The orders Ulotrichales and Ulvales are separated from the clade formed by the remaining orders of siphonous and siphonocladous Ulvophyceae (Caulerpales, Siphonocladales /Cladophorales [S/C] complex, and the Dasycladales), by the Chlorophyceae and Pleurastrophyceae. Our results suggest that the Ulvophyceae is not a monophyletic group. Examination of inter- and intra-ordinal relationships within the siphonous and siphonocladous ulvophycean algae revealed that Cladophora, Chaetomorpha, Anadyomene, Microdictyon, Cladophoropsis and Dictyosphaeria form a clade. Thus the hypothesis, based on ultrastructural features, that the Siphonocladales and Cladophorales are closely related is supported. Also, the Caulerpales is a monophyletic group with two lineages; Caulerpa, Halimeda, and Udotea comprise one, and Bryopsis and Codium comprise the other. The Dasycladales (Cymopolia and Batophora) also forms a clade, but this clade is not inferred to be the sister group to the S/C complex as has been proposed. Instead, it is either the sister taxon to the Caulerpales or basal to the Caulerpales and S/C clade The Trentepohliales is also included at the base of the siphonous and siphonocladous ulvophycean clade. The Pleurastrophyceae, which, like the Ulvophyceae, posses a counter-clockwise arrangement of flagellar basal bodies, are more closely related to the Chlorophyceae than to the Ulvophyceae based on rRNA sequences. Thus, the arrangement of basal bodies does not diagnose a monophyletic group. Previously reported hypotheses of phylogenetic relationships of ulvophycean algae were tested. In each case, additional evolutionary steps were required to obtain the proposed relationships. Relationships of ulvophycean algae to other classes of green algae are discussed.  相似文献   

2.
Partial sequences from the nuclear-encoded 18S and 26S ribosomal RNA molecules from representatives of the five classes of Chlorophyta sensu Mattox and Stewart (1984) were analyzed cladistically in a study of the phylogenetic relationships among the Micromonadophyceae, Pleurastrophyceae, and other green algae. The sequence data indicate that the Micromonadophyceae (= Prasinophyceae) is not monophyletic but comprises at least three lineages occupying a basal position among the green algae. Though the Pleurastrophyceae and the Ulvophyceae both possess counter-clockwise basal body orientations, the sequence data indicate that the Pleurastrophyceae is the sister group to the Chlorophyceae. The molecular data alone do not resolve the monophyly of the Pleurastrophyceae or the Ulvophyceae; however, a combined data set of molecular and non-molecular characters support a monophyletic Pleurastrophyceae. Analyses with user-defined tree topologies and the bootstrap method of character resampling indicate that the relationships shown in the most parasimonious cladograms are well supported by the character data.  相似文献   

3.
依据在云南富源中三叠世法郎组竹杆坡段发现的新材料,对关岭贵州空棘鱼(Guizhoucoelacanthus guanlingensis)进行了补充描述,并修订了鼻骨、顶骨、后顶骨、额外肩胛骨、眶后骨、偶鳍、鳞片等特征。系统发育分析表明,贵州空棘鱼属与Whiteia+Piveteauia构成姐妹群,其共有离征包括:两对顶骨的大小相近,第一背鳍鳍条数小于8。建议将贵州空棘鱼属归入怀特鱼科(Whiteiidae)。  相似文献   

4.
I examined three aspects of the cladistic treatment of a set of 17 F1 hybrids of known parental origin: (1) impact of hybrids on consistency index (CI) and number of most parsimonious trees (Trees), (2) placement of hybrids in cladograms, and (3) impact of hybrids on hypotheses of relationship among species. The hybrids were added singly and in randomly selected sets of two to five to a data set composed of Central American species of Aphelandra (including the parents of all hybrids). Compared to analyses with the same number of OTUs all of which were species, the analyses with hybrids yielded results with significantly higher CI. There was no difference in Trees between analyses with hybrids versus species. There was thus no evidence that hybrids would appear to be more problematic for cladistic methods than species. Accordingly, hybrids will not be readily identifiable as taxa that cause marked change in these indices. About % of the hybrids were placed as the cladistically basal members of the lineage that included the most apomorphic parent. Relatively apomorphic hybrids were placed proximate to the most derived parent (ca. 13% of hybrids). Other placements occurred more rarely. The most frequent placements of hybrids thus did not distinguish them from normal intermediate or apomorphic taxa. When analyses with hybrids yielded multiple most parsimonious trees, these were no more different from each other than were the equally parsimonious trees that resulted from analyses with species. Most analyses with one or two hybrids resulted in minor or no change in topology. When hybrids caused topological change, they frequently caused rearrangements of weakly supported portions of the cladogram that did not include their parents. When they disrupted the cladistic placement of their parents, they often caused their parents to change positions, with at least one topology bringing the parental lineages into closer proximity with the hybrid placed between them. Hybrids between parents from the two main lineages of the group caused total cladistic restructuring. In fact, the degree of relationship between a hybrid's parents (measured by both cladistic and patristic distance) was strongly correlated with CI (negatively) and with the degree of disturbance to cladistic relationships (positively). Thus, hybrids between distantly related parents resulted in cladograms with low CI and major topological changes. This study suggests that hybrids are unlikely to cause breakdown of cladistic structure unless they are between distantly related parents. However, these results also indicate that cladistics may not be specially useful in distinguishing hybrids from normal taxa. The applicability of these results to other kinds of hybrids is examined and the likely cladistic treatment of hybrids using other sources of data is discussed.  相似文献   

5.
在形态学研究的基础上,配方选择了12个特征,利用Hennig86程序包,以支序分析探讨了中国蝗总科昆虫科间的系统发育关系。结果表明蝗虫类昆虫稳定的分为两大类,即癞蝗类和蝗类,本文建议蝗虫类昆虫分为分为两个总科较宜。长腹蝗亚科似归入斑腿蝗亚科更为合理;而皱腹亚科则应提升为独立科。  相似文献   

6.
The genus Chlamydomonas Ehrenberg may contain as many as 450 described species. Morphological, physiological and molecular data show that variation among some Chlamydomonas species can he great, leading to speculation that multiple, generic-level lineages exist within this genus. The most recent systematic studies of Chlamydomonas have led to proposals of nine distinct morphological and 15 distinct sporangial autolysin groups. Partial sequences from the nuclear small subunit rRNAs from 14 Chlamydomonas species representing 12 autolysin and four morphological groups, and from three flagellates thought to he related to Chlamydomonas were determined in a phylogenetic study of relationships among these algae. Sequence comparisons among some Chlamydomonas species revealed differences comparable to the sequence divergence between soybeans and cycads. Cladistic analysis of the sequence data suggests that multiple lineages exist among species of Chlamydomonas. Some of these lineages represent alliances of both Chlamydomonas and non-Chlamydomonas taxa; thus, the current taxonomy does not reflect natural, or monophyletic, groups. Collectively, these lineages may represent distinct families or even orders.  相似文献   

7.
在已有比较形态学研究基础上,本文选择了15个特征方面(外生殖器为主)的74个新征,以支序分析方法探讨了缘蝽科族(或亚科)的系统发育关系。结果表明棒缘蝽亚科、希缘蝽族、沟缘蝽族较为原始,与其余类群差异较大,缘蝽科的范围值得进一步研究;除Chariesterini外的缘蝽亚科是高等的缘蝽类群;Chariesterini似应从缘蝽亚科中独立出来;狭义巨缘蝽族以及萧的鼻缘蝽族、梭缘蝽族、昧缘蝽族、曼缘蝽族成立;拟黛缘蝽属、副黛缘蝽属、华黛缘蝽属、异黛缘蝽属应从”黛缘蝽族”中分别独立出来成立新族,即拟黛缘蝽族、副黛缘蝽族、华黛缘蝽族和异黛缘蝽族,以使原有的黛缘蝽族成为自然类群。  相似文献   

8.
记述了南海北部近海水螅虫总纲4新种和2新纪录,即自育水母纲的顶胃穴水母岛Sminthea apicigastrica Xu,Huang et Du,sp.nov.,水螅水母纲的距拟双手水母Codonorchis calcariformis Xu,Huang et Guo,sp.nov.,南海多管水母Aequorea nanhainensis Xu,Huang et Du,sp.nov.,四手多管水母Aequorea tetranema Xu,Huang et Du,sp.nov.,深水拟单手水母Paragotoea bathybia Kramp,1942和母螅镰螅水母Zanclea medusopolypata Boero,Bouillon et Gravili,2000.并讨论了新种与近缘种的区别,模式标本保存在中国水产科学研究院南海水产研究所.  相似文献   

9.
Biased transitions are common throughout the tree of life. The class hydrozoa is no exception, having lost the feeding medusa stage at least 70 times. The family hydractiniidae includes one lineage with pelagic medusae (Podocoryna) and several without (e.g., Hydractinia). The benthic colony stage also varies widely in host specificity and in colony form. The five‐gene phylogeny presented here requires multiple transitions between character states for medusae, host specificity, and colony phenotype. Significant phylogenetic correlations exist between medusoid form, colony morphology, and host specificity. Species with nonfeeding medusae are usually specialized on a single host type, and reticulate colonies are correlated with nonmotile hosts. The history of feeding medusae is less certain. Podocoryna is nested within five lineages lacking medusae. This requires either repeated losses of medusae, or the remarkable re‐evolution of a feeding medusa after at least 150 million years. Traditional ancestral reconstruction favors medusa regain, but a likelihood framework testing biased transitions cannot distinguish between multiple losses versus regain. A hypothesis of multiple losses of feeding medusae requires transient selection pressure favoring such a loss. Populations of species with feeding medusae are always locally rare and lack of feeding medusae does not result in restricted species distribution around the world.  相似文献   

10.
材料系于2007年(1,4,7,10月)、2008年(1,7月)和2009年(1月)在北部湾水域采集的,调查海区共设52站,共采集364份样品。经分析鉴定出67种水母,其中有3新种和中国2新纪录,主辐特古水母Tregouboiva perradialis Xu,Huang et Du,sp. nov.,泡真囊水母Euphysora vacuola Xu,Huang et Guo,sp. nov.,波腺侧丝水母Helgicirrha sinuatus Xu,Huang et Du,sp. nov.,艾格帝纹水母Timoides agassizi Bigelow,1904和大腺美螅水母Clytia macrogonia Bouillon,1984。此外,还报道了20种水母为北部湾新纪录。模式标本保存在中国水产科学研究院南海水产研究所。主辐特古水母,新种Tregoubovia perradialis Xu,Huang et Du,sp. nov.鉴别特征伞近钟形,外伞有16条双层向心肋; 垂管很大,近方形,约为内伞腔深度4/5;口有4个延长成触手状的口唇,具环状刺胞,无末端刺胞球;隔膜短;4个大的椭圆形生殖腺,几乎覆盖整个垂管主辐位;伞缘无缘触手或缘基球;无眼点。正模(BG 001),北部湾S30站(17°30’N,107°30’E;水深70m),2008-07-06,梁新采(南海水产研究所)。词源:新种种名源自拉丁词perradialis,意为生殖腺位于垂管主辐位。泡真囊水母,新种Euphysora vacuola Xu,Huang et Guo,sp. nov.鉴别特征伞有钝圆形顶突;垂管长椭圆形,约有1/2长度超出缘膜口外,垂管基部很宽,覆盖着浓密泡状细胞组织;4条辐管上部与扩大的垂管基部连接;生殖腺围绕着垂管壁;主触手很长,触手基球很大,呈卵圆形至球形,触手上具30~40个成排的背轴刺胞球,无末端膨大刺胞球,另3个触手基球退化,很小,同样大小,无丝状触手,每个基球具外胚层背距。正模(BG 006),北部湾C15站(20°N,109°E;水深44m),2007-07-25,梁新采(南海水产研究所)。副模(TB001),台湾海峡102站(23°40’N,118°44’E;水深54m),1988-06-29,黄加祺采(厦门大学海洋学系)。词源:新种种名源自拉丁词vacuola,意为该种在垂管基部覆盖浓密泡状细胞组织。波腺侧丝水母,新种 Helgicirrha sinuatus Xu,Huang et Du,sp.nov.鉴别特征伞略扁于半球形;胃柄长,约有1/2超出缘膜口外,垂管短小,口有4个短的略为向上弯曲折叠的口唇;生殖腺深波形,位于辐管远端1/3处; 16 ~ 24 条缘触手,每条触手具2对侧丝,每2条触手间有3~5个缘疣,具1对侧丝和3~4个平衡囊,每个平衡囊有2~4个平衡石;所有触手和缘疣基部均有向轴排泄乳突。正模(BG 007),副模(BG 008-009),北部湾S18站( 18°45’N,106°45’E;水深53m),2007-04-15,梁新采(南海水产研究所)。词源:新种种名源自拉丁词sinuatus,意为该种生殖腺深波状。  相似文献   

11.
12.
Abstract:  Study of corallum shape in Siderastrea and Solenastraea colonies collected from Pleistocene Bermont strata in western Palm Beach County, Florida, indicates that the corals are rotatory, formed by rolling during growth on the Pleistocene sea floor. Growth of a radial and centrifugal nature away from the corallum centre suggests that rolling was sufficiently frequent and energetic to maintain the health of individual polyps along the skeleton's entire spherical surface with no evidence of growth stoppage. Post-mortem sponge boring accompanied by that of sipunculid worms and boring by the bivalves Gastrochaena and Lithophaga during coral colony life is common. Colonization by cirripeds (barnacles) on some live colonies also occurred, but these are most commonly overgrown. Boring of rotatory coralla decreased the mass of the skeleton and probably increased the ease and frequency of rolling. Comparison with modern rotatory specimens of S. radians from Rodriguez Bank indicates that the Pleistocene corals were not greatly modified during diagenesis, given their comparable densities. Diameters of both groups of corals are utilised to calculate levels of shear velocities necessary to move them, based on hydrodynamics of rounded sediment of comparable size. The presence of these rotatory coralla, by analogy, strongly suggest that Bermont sediments in the study area accumulated on shallow shelf areas populated by numerous other free-living corals along with fewer fixed corals, accompanying a diverse molluscan assemblage, all indicative of a Thalassia (turtle-grass) community. Nearshore, wave data recorded along Florida's present-day east coast, in contrast to conditions along the west coast, indicate that sufficient wave-generated velocities are present to cause regular rotation of Siderastrea and Solenastraea , and would likely have done so during the Pleistocene.  相似文献   

13.
本文描述了我国四川峨嵋灯影组麦地坪段原始锥石类中的一个罕见的具有三个柱面的Emeiconulariatrigemmegen.etsp.nov.。并与具有四个柱面的Carinachitids和六个柱面的Hexangulaconularids进行了比较讨论。经扫描电镜观察,该属种壳体由二层组成。内层由棱柱状胶结物组成,外层由微粒状磷酸盐颗粒组成。它们被认为是经过改造了的原生磷酸盐质壳壁。  相似文献   

14.
本文在已有大量比较形态学研究和各科支序分析研究基础上,对缘蝽总科的科、亚科、族等亚群的系统发育关系作了支序分析研究,结果表明,缘蝽总科、蛛缘蝽科、姬缘蝽科的单系群地位得到证明。而缘蝽科由于其棒缘蝽亚科和希缘蝽亚科分别占据支序图的两个最低位置,它们在缘蝽总科中具有较多的原始特征,缘蝽亚科的Chariesterini族与南美缘蝽亚科互为姐妹群而与缘蝽亚科其它族差异较大;姬缘蝽科的红缘蝽亚科处在该分支的最高位置且与姬缘蝽亚科中的Harmostini族互为姐妹群,与姬缘蝽亚科其它族关系也较近,因而传统的缘蝽科、缘蝽亚科、姬缘蝽亚科为并系群。为使各分类单元为单系群即自然类群,使分类系统更忠实于系统发育关系,本文将棒缘蝽亚科和希缘蝽亚科分别提升为科,Chariesterini族提升为亚科;红缘蝽亚科降为族,姬缘蝽科不设亚科。据上述分类学变动提出了缘蝽总科族以上高级阶分类系统。  相似文献   

15.
Abstract— A cladistic analysis of the endemic South American family Tristiridae was performed using 29 characters from external morphology and the genitalia. Polarity of characters was based on the outgroup comparison method. One most parsimonious cladogram of 54 steps was obtained, from which a classification of the family Tristiridae was constructed. The analysis of phylogenetic relationships showed that the different kinds of characters define taxa at different levels in the cladogram. Those mostly from the phallic complex define suprageneric taxa while those from external morphology characterize genera. It is hypothesized that in Tristiridae differentiation of the phallic complex preceded differentiation of external morphology and that characters from the phallic complex arc less conservative than those from the external morphology.  相似文献   

16.
Abstract  A cladistic analysis of tribes and subfamilies included in Coreidae, Rhopalidae and Alydidae of the superfamily Coreoidea, based on 60 apomorphies, has been made in the present paper. The results indicate that both the Pseudophloeinae and Hydarinae of Coreidae are monophyletic and occupy the two lowest positions in the cladogram in comparison with the other coreid groups; the tribe Chariesterini of Coreinae is a sister group with Meropachydinae; Serinethini (the only tribe of "Serinethinae", Rhopalidae) is a sister group with Harmostini of Rhopalinae in the rhopalid offset of the cladogram. These mean the traditional Coreidae, Coreinae, and Rhopalinae are paraphyletic groups. According to the results of the snalysis and their characteristics, the "Pseudophloeinae" and "Hydarinae" are raised to family category respectively, the tribe Chariesterini is raised to subfamily category in family Coreidae; the traditional Serinethinae is suppressed to tribe category (no subfamilial ranks will be set up in Rhopalidae), so that all the groups are natural and the paraphyletic groups are avoided in the superfamily, and no this basis a new higher classification system of Coreoidea is suggested.  相似文献   

17.
A Bayesian analysis, utilizing a combined data set developed from the small subunit (SSU) and large subunit (LSU) rDNA gene sequences, was used to resolve relationships and clarify generic boundaries among 84 strains of plastid‐containing euglenophytes representing 11 genera. The analysis produced a tree with three major clades: a Phacus and Lepocinlis clade, a Discoplastis clade, and a Euglena, Colacium, Trachelomonas, Strombomonas, Monomorphina, and Cryptoglena clade. The majority of the species in the genus Euglena formed a well‐supported clade, but two species formed a separate clade near the base of the tree. A new genus, Discoplastis, was erected to accommodate these taxa, thus making the genus Euglena monophyletic. The analysis also supported the monophyly of Colacium, Trachelomonas, Strombomonas, Monomorphina, and Cryptoglena, which formed two subclades sister to the Euglena clade. Colacium, Trachelomonas, and Strombomonas, all of which produce copious amounts of mucilage to form loricas or mucilaginous stalks, formed a well‐supported lineage. Our analysis supported retaining Strombomonas and Trachelomonas as separate genera. Monomorphina and Cryptoglena formed two well‐supported clades that were sister to the Colacium, Trachelomonas, and Strombomonas clade. Phacus and Lepocinclis, both of which have numerous small discoid chloroplasts without pyrenoids and lack peristaltic euglenoid movement (metaboly), formed a well‐supported monophyletic lineage that was sister to the larger Euglena through Cryptoglena containing clade. This study demonstrated that increased taxon sampling, multiple genes, and combined data sets provided increased support for internal nodes on the euglenoid phylogenetic tree and resolved relationships among the major genera in the photosynthetic euglenoid lineage.  相似文献   

18.
THE RELATIONSHIP BETWEEN EVOLUTIONARY THEORY AND PHYLOGENETIC ANALYSIS   总被引:1,自引:0,他引:1  
The relationship between phylogenetic reconstruction and evolutionary theory is reassessed. It is argued here that phylogenies, and evolutionary principles, should be analysed initially as independently from each other as possible. Only then can they be used to test one another. If the phylogenies and evolutionary principles are totally consistent with one another, this consilience of independent lines of evidence increases confidence in both. If, however, there is a conflict, then one should assess the relative support for each hypothesis, and tentatively accept the more strongly supported one. We review examples where the phylogenetic hypothesis is preferred over the evolutionary principle, and vice versa, and instances where the conflict cannot be readily resolved. Because the analyses of pattern and process must initially be kept separate, the temporal order in which they are performed is unimportant. Therefore, the widespread methodology of always proceeding from cladogram to evolutionary ‘scenario’ cannot be justified philosophically. Such an approach means that cladograms cannot be properly tested against evolutionary principles, and that evolutionary ‘scenarios’ have no independent standing. Instead, we propose the ‘consilience’ approach where phylogenetic and evolutionary hypotheses are formulated independently from each other and then examined for agreement.  相似文献   

19.
An approximately 1400‐bp region of the 16S rRNA gene was sequenced for 10 polar or near‐polar strains putatively placed in the Oscillatorialean genera Oscillatoria, Phormidium, and Lyngbya obtained from the University of Toronto Culture Collection to assess phylogenetic relationships. The strains were also examined for thylakoid structure and cell division type with TEM as well as traditional morphology with LM. Phylogenetic trees constructed using parsimony, distance, and maximum likelihood methods were similar in topology. If the original epithets applied to the sequenced strains (both polar and those from GenBank) were used, it was clear that taxa were not monophyletic. However, using the revised taxonomic system of Anagnostidis and Komárek, we were able to reassign these strains to their current correct taxa (species, genus, and family). When these assignments were made, it was determined that the molecular sequence data analyses were congruent with morphology and ultrastructure. Nine of the polar strains were found to be new species, and eight were described as such: Arthronema gygaxiana Casamatta et Johansen sp. nov., Pseudanabaena tremula Johansen et Casamatta sp. nov., Leptolyngbya angustata Casamatta et Johansen sp. nov., Phormidium lumbricale Johansen et Casamatta sp. nov., Microcoleus glaciei Johansen et Casamatta sp. nov., Microcoleus rushforthii Johansen et Casamatta sp. nov., Microcoleus antarcticus Casamatta et Johansen sp. nov., Microcoleus acremannii Casamatta et Johansen sp. nov. Some genera (Leptolyngbya and Microcoleus) were clearly not monophyletic and require future revision.  相似文献   

20.
画眉科鸟类系统发育及分类地位商榷   总被引:2,自引:0,他引:2  
原记录在中国有分布的鹛类计142种,占世界鹛类纪录种总数284种的50%.由于该类群的种类繁多,形态和生态习性多样,其分类问题历来受分类学者的关注,且争议较大.本文尝试以分子生物学手段来解决传统分类中遗留的问题.在系统发育分析中共有20属59种鹛类作为内群、14个相关物种作为外群,分子标记分别采用线粒体细胞色素b(Cty 6,846 bp)和核内重组引导基因(RAG-1,870 bp),以最大似然法和贝叶斯法重建系统发育树.结果表明,画眉科鸟类明显被分为2大支系,一支由噪鹛Garrulax、希鹛Minla、薮鹛Liocichla、相思鸟Leiothrix、奇鹛Heterophasia、穗鹛Stachyris、钩嘴鹛Pomatorhinus、凤鹛Yuhina、及部分雀鹛Alcippe等属的种类构成,另一支由鸦雀属Paradoxornis和山鹛Rhopophilus pekinensis、及部分雀鹛属的种类构成,2支都有相当高的支持率;各个属之间的相互关系大致得到解决,传统分类体系中噪鹛属、雀鹛属、鸦雀属、凤鹛属、穗鹛属的单系性不能成立;证实绣眼鸟属Zosteropidae、山鹛和林莺属Sylvia鸟类的亲缘关系较近,而白腹凤鹛Yuhina.zantholeuca、鹏鹛属Pteruthius和文须雀Panurus biarmicus与鹛类的亲缘关系较远;并提出小鳞胸鹪鹛Pnoepyga pusilla有可能不是画眉科种类,其分类地位需要重新认识.  相似文献   

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