中国蚌螨属支序分类分析(蜱螨亚纲:蚌螨科)

选择35个特征对我国蚌螨属15种的支序分析结果表明:蚌螨P-Ⅳ(胫节)端腹部的指状突是将它们聚集成两群的主要特征.今村蚌螨P-Ⅳ端腹部仅具有短矩,与外群最近,认为是我国的蚌螨属水螨中最原始的种类;雌螨前殖吸盘板的形态影响戊蚌螨亚属与多盘蚌螨亚属的种类聚类,由此推测可以将蚌螨P-Ⅳ端腹部的指状突与雌螨前殖吸盘板的形态也作为蚌螨亚属的区分特征.由于殖吸盘结构简单是祖征态之一,因此认为具有5对殖吸盘的邻近蚌螨比6对殖吸盘的厚蚌螨更原始.雌螨具有1对殖吸盘板的寄蚌螨亚属种类与沃蚌螨亚属种类在支序系统树中形成姊妹群,结果支持Vidrine 将沃蚌螨亚属从寄蚌螨亚属中分离的修订.     

Evaluating the efficacy of continuous quantitative characters for reconstructing the phylogeny of a morphologically homogeneous spider taxon (Araneae, Mygalomorphae, Antrodiaetidae, Antrodiaetus)

The use of continuous quantitative characters for phylogenetic analyses has long been contentious in the systematics literature. Recent studies argue for and against their use, but there have been relatively few attempts to evaluate whether these characters provide an accurate estimate of phylogeny, despite the fact that a number of methods have been developed to analyze these types of data for phylogenetic inference. A tree topology will be produced for a given methodology and set of characters, but little can be concluded with regards to the accuracy of phylogenetic signal without an independent evaluation of those characters. We assess the performance of continuous quantitative characters for the mygalomorph spider genus Antrodiaetus, a group that is morphologically homogeneous and one for which few discrete (morphological) characters have been observed. Phylogenetic signal contained in continuous quantitative characters is compared to an independently derived phylogeny inferred on the basis of multiple nuclear and mitochondrial gene loci. Tree topology randomizations, regression techniques, and topological tests all demonstrate that continuous quantitative characters in Antrodiaetus conflict with the phylogenetic signal contained in the gene trees. Our results show that the use of continuous quantitative characters for phylogenetic reconstruction may be inappropriate for reconstructing Antrodiaetus phylogeny and indicate that due caution should be exercised before employing this character type in the absence of other independently derived sources of characters.     

Systematics of naviculoid diatoms (Bacillariophyta): A preliminary analysis of protoplast and frustule characters for family and order level classification

The relationships between 49 naviculoid diatoms, currently arranged in 14 families and four orders were investigated using cladistic analysis in order to test the types of characters used in diatom systematics and to assess how well the current classification reflects possible phylogenetic relationships in this group. Some of the families and orders comprise taxa with different protoplast characters, or taxa with similar protoplast arrangements are placed in separate families or orders. Therefore as both cell wall and protoplast characters were used, three analyses were undertaken; total data, protoplast data and frustule data. The analyses support the recognition of the Mastogloiales (unequivocally) and the Cymbellales (largely) but indicate that some of the familial groupings are more ambiguous. The members of the Berkeleyaceae, Berkeleya, Parlibellus and Climaconeis, were never grouped together and Achnanthes brevipes never grouped with the other monoraphid diatoms, but usually with members of the Mastogloiales (total and protoplast data). Similarly, Round et al.’s familial groupings within the Cymbellales do not emerge from our analyses. Our results support the hypothesis that monoraphid genera have arisen independently from different naviculoid diatoms, and that Achnanthes sensu stricto should be transferred to the Mastogloiales. Some of the problems associated with incomplete information and inaccurate terminology are discussed briefly.     

A palaeontological and phylogenetical analysis of squaliform sharks (Chondrichthyes: Squaliformes) based on dental characters

Squaliformes comprise the major proportion of modern deep-water sharks, yet their fossil history and phylogenetic relationships are still poorly understood. New analyses have been undertaken, however, and new living and fossil species have been discovered during the past 10 years. A cladistic analysis involving 29 dental characters has been made and most living and fossil genera are included. On the basis of their dental morphology, the monophyly of the Squaliformes can be supported if the fossil genus Protospinax is excluded. The traditional phylogenetic positions of most living genera, Protosqualus, Cretascymnus and Eoetmopterus, are confirmed despite the fact that the Oxynotidae, Etmopterinae, Palaeomicroides, Proetmopterus and Microetmopterus have some atypical phylogenetic relationships within the Squaliformes. The addition of the palaeontological data in a phylogenetic tree including fossil and living Squaliformes demonstrates some gaps in the fossil record. Nevertheless, and as a consequence of that stratigraphy-phylogeny inference, two particular events can be pinpointed in the history of the Squaliformes: the first one occurs after the major Cenomanian-Turonian anoxic event and the second one after the Cretaceous/Tertiary crisis. The first radiation involves the majority of the living Squaliformes (Somniosinae, Centrophorinae, most of the Etmopterinae, Oxynotinae) in deep-sea waters, the second, the more epipelagic sharks (most of the Dalatiidae), suggesting a secondary adaptation to more shallow environments.     

Molecular systematics of Solanum section Lycopersicum (Lycopersicon) using the nuclear ITS rDNA region

The phylogenetic relationships of all nine known tomato species of Solanum section Lycopersicum, together with other Solanum sections and species from several related genera, were investigated using parsimony analysis of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA (rDNA). Most parsimonious reconstructions divided the section Lycopersicum into three clades, reflecting their mating behaviour and fruit colour. Data from sequencing studies were congruent with those from morphological and other molecular investigations, and provided detailed information concerning species relationships. Received: 11 July 2000 / Accepted: 17 April 2001     

A cladistic analysis of interspecific relationships ofSaguinus

The dental and cranial morphologies of all species ofSaguinus, S. oedipus, S. geoffroyi, S. leucopus, S. nigricollis, S. fuscicollis, S. labiatus, S. mystax, S. imperator, S. bicolor, andS. midas are examined. The following hypotheses are developed by cladistic methodology, using only synapomorphic characters to assess the interspecific relationships ofSaguinus.Saguinus are divided into two main groups; one consists ofS. oedipus, S. geoffroyi, andS. leucopus, and the other includesS. inustus, S. nigricollis, S. fuscicollis, S. labiatus, S. mystax, S. imperator, S. bicolor, andS. midas. In the former group,S. oedipus is more closely related toS. geoffroyi than either is toS. leucopus. In the latter group,S. labiatus, S. mystax, andS. imperator are classified into one group, andS. bicolor andS. midas form one monophyletic group.     

Evolved RNA Secondary Structure and the Rooting of the Universal Tree of Life

The origin and diversification of RNA secondary structure were traced using cladistic methods. Structural components were coded as polarized and ordered multi-state characters, following a model of character state transformation outlined by considerations in statistical mechanics. Several classes of functional RNA were analyzed, including ribosomal RNA (rRNA). Considerable phylogenetic signal was present in their secondary structure. The intrinsically rooted phylogenies reconstructed from evolved RNA structure depicted those derived from nucleic acid sequence at all taxonomical levels, and grouped organisms in concordance with traditional classification, especially in the archaeal and eukaryal domains. Natural selection appears therefore to operate early in the information flow that originates in sequence and ends in an adapted phenotype. When examining the hierarchical classification of the living world, phylogenetic analysis of secondary structure of the small and large rRNA subunits reconstructed a universal tree of life that branched in three monophyletic groups corresponding to Eucarya, Archaea, and Bacteria, and was rooted in the eukaryotic branch. Ribosomal characters involved in the translational cycle could be easily traced and showed that transfer RNA (tRNA) binding domains in the large rRNA subunit evolved concurrently with the rest of the rRNA molecule. Results suggest it is equally parsimonious to consider that ancestral unicellular eukaryotes or prokaryotes gave rise to all extant life forms and provide a rare insight into the early evolution of nucleic acid and protein biosynthesis. Received: 13 September 2000 / Accepted: 27 August 2001     

Dichotomy of major bacterial phyla inferred from gene arrangement comparisons

A computer search for gene arrangements that are present in Gram-positive bacteria but are absent from Proteobacteria and vice versa was carried out. Four such arrangements were detected, based on which major bacterial phyla were divided into two groups; Thermotoga, Deinococcus-Thermus, Chloroflexi (green non-sulfur bacteria), and Fusobacteria, represent Gram-positive bacterial gene arrangements, while Aquifex, Spirochetes, Planctomycetes, Chlorobi (green sulfur bacteria), Bacteroides show Proteobacterial arrangements. The division is almost consistent with another partition of the major phyla based on the comparison of domain architectures of RNA polymerase subunits and sigma factor, suggesting a fundamental split of the major bacterial phyla at an early stage of bacterial evolution.     

Phylogenetic relationships of the stromateoid fishes (Perciformes)

The phylogenetic relationships of all 16 genera (plus Psenes pellucidus) of the suborder Stromateoidei were estimated cladistically based on 43 osteological, myological, and external characters. Thirty equally parsimonious trees were obtained. Based on the strict consensus tree, Centrolophidae was nonmonophyletic, Psenopsis being placed as a sister group of a clade comprising Amarsipus, Ariomma, nomeids, Tetragonurus, and stromateids. Schedophilus formed a sister group relationship with Seriolella. The relationships among the Centrolophus, Hyperoglyphe, Icichthys, Tubbia, Schedophilus+Seriolella clade, and Psenopsis+Amarsipus+Ariomma+nomeids+Tetragonurus+stromateids clade were unresolved. Amarsipus, which is unique within the suborder in lacking a pharyngeal sac, was nested within the stromateoid clade, being a sister group of the clade including Ariomma, nomeids, Tetragonurus, and stromateids. The absence of a pharyngeal sac in Amarsipus was interpreted as a reversal, its presence in the Stromateoidei therefore being considered as a synapomorphy. Ariomma was placed as the sister group of a clade comprising nomeids, Tetragonurus, and stromateids. Monophyly of the Nomeidae and Stromateidae were supported by 2 and 11 synapomorphies, respectively.