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1.
在对毛锦藓科的分类学修订中,我们报道3个种和1变种在中国的新分布记录,它们是:外弯小锦藓Brotherella recurvans、纤枝疣胞藓Clastobryum cuculligerum、海岛麻锦藓Taxithelium liukiuense、扭尖金枝藓阔叶变种Trismegistia calderensis var. rigida。这些新记录物种的标本分别采自海南、香港和云南。  相似文献   

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Vicariant and climatic cycling speciation hypotheses of the 'sand gobies' belonging to the genera Pomatoschistus, Gobiusculus, Knipowitschia, and Economidichthys are tested using molecular phylogenies constructed of nuclear DNA (ITS1 locus) and mitochondrial DNA (12S and 16S fragments). These gobies are among the most abundant in the Eastern Atlantic-Mediterranean region, and play an important role in the ecosystem. Considerable ITS1 length differences, primarily due to the presence of several tandem repeats, were found between species and even within individuals. Therefore, phylogenetic analyses focused on fragments of the 12S and 16S mtDNA region that have been sequenced for 16 goby taxa. The 'sand gobies' clustered as a monophyletic group as proposed on morphological grounds. However, G. flavescens, E. pygmaeus, and K. punctatissima clustered within the Pomatoschistus species, pointing to a paraphyletic origin of these genera. Furthermore, the genetic divergence between P. minutus from the Adriatic Sea versus the Atlantic-Mediterranean region was as high as the divergence within the P. minutus complex, suggesting that P. minutus from the Adriatic Sea should be considered as a distinct species. The "star" phylogeny might suggest that these gobies evolved in a very short time period, possibly linked to the drastic alterations in the Mediterranean Sea during and immediately after the Messinian salinity crisis at the end of the Miocene. The freshwater life-style appeared monophyletic; equating its origin with the salinity crisis resulted in a molecular clock estimate of 1.4% divergence per million years. The last common ancestor probably occupied sandy bottoms and a coastal niche while several species subsequently adapted to new habitats (pelagic, freshwater or stenohaline). The origin of the shallowest clades dated back to the glacial cycling during the Pleistocene epoch.  相似文献   

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The trend of species diversity and spatiotemporal distribution of spherical radiolarians of the genus Entactinia Foreman, 1963 in the Permian Period is analyzed. The center of origin of Permian entactinians in the Cis-Ural Paleobasin is established in the area of the modern interfluve of the Ural River and latitudinal current of the Belaya River on the Southern Urals. It is shown that the species composition of this genus almost completely changed in certain Permian epochs. Two forefather species of each new pleiad of Early, Middle, and Late Permian are revealed: Entactinia parapycnoclada and E. tyrrelli. Two new species of the Lower Permian radiolarians from the Southern Urals and Northern Mugodzhary, E. chernykhi sp. nov. and E. subquadrata sp. nov., are described.  相似文献   

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Eutrema edwardsii R.Br. (Brassicaceae) is an arctic-alpine mustard with a circumpolar distribution. Its closest relative, Eutrema penlandii Rollins, is a federally listed, threatened species that is endemic to the Mosquito Range in the Southern Rocky Mountains of Colorado, USA. As part of a larger project addressing the systematics of this species complex in North America, we conducted chromosome counts, flow cytometry, and allozyme analysis to test the hypothesis that these taxa comprise an autopolyploid complex. Within that context, it should be noted that a chromosome count has not been reported previously for E. penlandii. Results obtained from mitotic counts obtained for two populations of E. penlandii reveal this taxon to be diploid. Diploidy was confirmed using flow cytometry for an additional 15 individuals representing four populations. Previously published chromosome counts for E. edwardsii reveal a polyploid complex of tetraploid, hexaploid, and octaploid populations for which an autopolyploid origin has been presumed. However, allozyme analysis revealed an allopolyploid origin for E. edwardsii, as evidenced from fixed heterozygosity at six loci. Although our data suggest that E. penlandii is a close relative of one of the progenitors of E. edwardsii, the taxonomic identity of the other progenitor(s) cannot be elucidated from these data. The data reported herein support the recognition of E. penlandii as taxonomically distinct, which has implications for conservation, and reveal cryptic variation within E. edwardsii.  相似文献   

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The demography and reproductive biology of three Epinephelus groupers (Serranidae), namely E. polyphekadion, E. tauvina, and E. howlandi in the Yaeyama Islands, Okinawa, were examined based on age assessment using otoliths and gonadal histology. The maximum ages for these three species were 26 year, 23 year, and 17 year. The von Bertalanffy growth functions were also determined for each species. The size and age at 50% female maturity were estimated to be 358 mm in total length (TL) and 6.0 year for E. polyphekadion, 371 mm TL and 6.7 year for E. tauvina, and 327 mm TL and 4.1 year for E. howlandi, respectively. Significant differences between the sexes in size and age frequencies were found in all three species, with males being larger and older than females, or transitional individuals. These results strongly indicated that the population of these three grouper species showed monandric protogynous hermaphroditism. The sex ratios of E. polyphekadion and E. tauvina were biased in favor of females, but that of E. howlandi was equivalent between sexes. The relative sizes of ripe testes indicated that the intensity of sperm competition varied among species suggesting different mating system of each species. Reproductive seasonality was similar among species, with active vitellogenesis coinciding with the annual rise in water temperature. The active spawning period was determined to be between April and May for E polyphekadion, in May for E. howlandi, and from March to June for E. tauvina.  相似文献   

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"Hit-and-run" transformation by adenovirus oncogenes   总被引:5,自引:0,他引:5  
According to classical concepts of viral oncogenesis, the persistence of virus-specific oncogenes is required to maintain the transformed cellular phenotype. In contrast, the "hit-and-run" hypothesis claims that viruses can mediate cellular transformation through an initial "hit," while maintenance of the transformed state is compatible with the loss ("run") of viral molecules. It is well established that the adenovirus E1A and E1B gene products can cooperatively transform primary human and rodent cells to a tumorigenic phenotype and that these cells permanently express the viral oncogenes. Additionally, recent studies have shown that the adenovirus E4 region encodes two novel oncoproteins, the products of E4orf6 and E4orf3, which cooperate with the viral E1A proteins to transform primary rat cells in an E1B-like fashion. Unexpectedly, however, cells transformed by E1A and either E4orf6 or E4orf3 fail to express the viral E4 gene products, and only a subset contain E1A proteins. In fact, the majority of these cells lack E4- and E1A-specific DNA sequences, indicating that transformation occurred through a hit-and-run mechanism. We provide evidence that the unusual transforming activities of the adenoviral oncoproteins may be due to their mutagenic potential. Our results strongly support the possibility that even tumors that lack any detectable virus-specific molecules can be of viral origin, which could have a significant impact on the use of adenoviral vectors for gene therapy.  相似文献   

8.
The Ukrainian brook lamprey Eudontomyzon mariae is the most widespread lamprey species in eastern Europe. Although E. mariae is generally considered a derivative of Eudontomyzon danfordi, an exclusively freshwater parasitic species, it has alternatively been suggested that it was recently derived from a now extinct anadromous Black Sea ancestor. Several non-parasitic lampreys and the landlocked sea lamprey, which have recently evolved from anadromous ancestors, still develop a seawater-type mitochondria-rich cell (SW-MRC) in their gills. In contrast, this cell type is not present in the gills of either Lampetra aepyptera, a non-parasitic lamprey of ancient origin, or the parasitic Ichthyomyzon unicuspis and I. castaneus that likewise have long evolutionary histories in fresh water. Eudontomyzon mariae from the Vistula River in the Baltic River basin does not possess SW-MRC, which is inconsistent with a recent origin from an anadromous ancestor. Mitochondrial DNA sequence data were thus used to infer the relationship between different populations of E. mariae and E. danfordi, and to reconstruct the transition from anadromy to freshwater residency. The results suggest that E. mariae evolved independently in the Baltic, Black, and Caspian Sea basins, and not recently from an anadromous ancestor. Although E. mariae in the Danube River may have arisen relatively recently from E. danfordi (differing by 0.7–1.1% in cytochrome b gene sequence), other E. mariae populations (including in the Vistula River) are genetically closer (0.6%) to the hypothetical ancestor of both E. mariae and E. danfordi. That ancestor was probably a freshwater resident, since SW-MRCs are not rapidly lost following confinement in fresh water.  相似文献   

9.
Chloroplast microsatellites for two Korean endemic species, Eranthis byunsanensis and E. pungdoensis (Ranunculaceae), were isolated to address the questions of their distributional patterns and evolutionary relationships, using next-generation sequencing. Twenty-four polymorphic chloroplast microsatellite markers for these two species were developed, and then characterized in 65 individuals (55 individuals of E. byunsanensis and 10 individuals of E. pungdoensis). The number of alleles per locus ranged from 2 to 9; the average number of alleles across all the loci scored 4.792. The unbiased diversity per locus ranged from 0.089 to 0.880; the unbiased diversity averaged over all the loci was 0.646. The developed markers were successfully amplified for three congeneric species, E. stellata, E. pinnatifida, and E. longistipitata. The markers developed in this study can provide a valuable and important tool for understanding genetic variations, population structures, evolutionary histories and phylogeography of E. byunsanensis, E. pungdoensis, and related species.  相似文献   

10.
Elaphoglossum mickeliorum, a new species from the eastern slopes of the Peruvian Andes, is here described and illustrated. It belongs to E. sect. Polytrichia, which is characterized by the presence of subulate scales and absence of hydathodes on the sterile leaves of adult sporophytes. Herbarium specimens of this new species were first collected by Alwyn H. Gentry ca. 40 years ago, but these got readily confused with E. erinaceum and went undescribed since then. The new species differs from members of the E. erinaceum complex by having a nearly continuous band of planar, nonsubulate scales along the laminar margins of sterile leaves. Based on this character, E. mickeliorum resembles species such as E. glaziovii, E. ornatum, and E. scolopendrifolium. It differs from these by the presence of minute glandular hairs on petioles and costae. A distribution map and a figure with line drawings are also provided. For comparative purposes, the line drawing includes E. blepharoglottis, which is here illustrated for the first time.  相似文献   

11.
Relations between the diversity of the fliC gene conditioning flagellum protein in E. coli and the source of the strain origin are presented. The fliC genes have been identified and characterized in commensal E. coli derived from 10 healthy animal species living in Zoo Safari Park (Poland). The fliC gene was found in 150 strains by the PCR method. The amplifiedfliC products revealed single bands within the range 1.26-2.16 kbp. Forty restriction patterns (classed by restriction analysis with the use of RsaI (PCR-RFLP RsaI; R-types) were determined. The neighbor-joining method was employed to illustrate the distribution of the kinds of R-types. There are 3-8 various R-types of a diversified frequency of occurrence in strains. Application of PCR-RFLP RsaI permitted the identification of alleles of fliC genes characteristic for E. coli and the estimation of their diversity among the animal species. The transmission ways of E. coli fliC+ between organisms of different species were determined and confirmed the role of transmission and horizontal gene transfer in the generation of the allelic diversity of fliC gene in natural E. coli populations.  相似文献   

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The black yeast genus Exophiala includes numerous potential opportunistic species that potentially cause systematic and disseminated infections in immunocompetent individuals. Species causing systemic disease have ability to grow at 37–40 °C, while others consistently lack thermotolerance and are involved in diseases of cold-blooded, waterborne vertebrates and occasionally invertebrates. We explain a fast and sensitive assay for recognition and identification of waterborne Exophiala species without sequencing. The ITS rDNA region of seven Exophiala species (E. equina, E. salmonis, E. opportunistica, E. pisciphila, E. aquamarina, E. angulospora and E. castellanii) along with the close relative Veronaea botryosa was sequenced and aligned for the design of specific padlock probes for the detection of characteristic single-nucleotide polymorphisms. The assay demonstrated to successfully amplify DNA of target fungi, allowing detection at the species level. Amplification products were visualized on 1% agarose gels to confirm specificity of probe–template binding. Amounts of reagents were reduced to prevent the generation of false positive results. The simplicity, tenderness, robustness and low expenses provide padlock probe assay (RCA) a definite place as a very practical method among isothermal approaches for DNA diagnostics.  相似文献   

13.
Hydraena is the largest genus within the water beetle family Hydraenidae, with ca. 1000 species distributed worldwide. Within this large genus some monophyletic groups of species are recognised, among them the "Haenydra" lineage, including ca. 90 species distributed in the western Palaearctic from the Iberian peninsula to Iran. Species of "Haenydra" have often very restricted distributions, and are typical of clean small rivers and streams. We obtained ca. 2.5Kb of mitochondrial and nuclear protein-code and ribosomal markers of 101 specimens of 69 species of "Haenydra", and used Bayesian and Maximum Likelihood phylogenetic methods to reconstruct their phylogeny and diversification history. We found a derived phylogenetic position of the "Haenydra" lineage within the genus Hydraena, as sister to the species of the Hydraenabisulcata group. Within "Haenydra" three main lineages were recognised, with poorly resolved relationships among them: the Hydraena iberica, Hydraena gracilis and Hydraena dentipes lineages, the former restricted to the Iberian peninsula but the latter two distributed through the whole north-Mediterranean area. A Bayesian relaxed molecular clock approach using a combined mitochondrial rate of 2% divergence per MY estimated the origin of "Haenydra" in the Tortonian, ca. 8Mya, and the main diversification and the origin of most extant species in the Pliocene and Pleistocene. We did not found evidence of a phylogenetic connection between the western and eastern species that could be traced to the Messinian salinity crisis, with dispersal only at small geographical scales (e.g. the colonisation of Corsica and Sardinia from NW Italy and SW France). The H. gracilis and H. iberica lineages were estimated to have diversified under a pure birth model with a speciation rate of 0.64 and 0.23 species/MY respectively, while the H. dentipes lineage was estimated to have a decreasing diversification rate with time, with an average rate of 0.29 sp/MY.  相似文献   

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The "masked" autoantibodies with polyspecific activity were found in the serum of healthy donors. It is shown that these antibodies are able to react with antigens after the ion exchange chromatography with QAE-sephadex. It was found that these "masked" antibodies are able to cross-react with DNA and lipopolysaccharides of wide-spread species of bacteria. The possible role of these antibodies as in protection of organism from the external antigens as in the origin of autoimmune diseases is discussed.  相似文献   

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Species are the most common currency by which biodiversity is measured, but species are not equivalent in "biodiversity value" because of differences in phylogenetic history and current population processes. Morphologically defined species in Sphagnum section Acutifolia (Bryophyta) were compared with regard to how phylogenetically distinct each is from its sister species and how much nucleotide variation each encompasses. Comparisons were based on sequence variation at seven nuclear and chloroplast loci. Assignment of collections to morphospecies accounted for about 57-75% of the overall nucleotide variation at the seven loci, but morphospecies differed greatly in how much nucleotide diversity they encompass. In addition, morphospecies varied widely in their genetic distinctiveness, estimated as the length of the stem branch from the most recent common ancestor and numbers of differentially fixed and shared polymorphic nucleotides among taxa. Levels of molecular diversity within morphospecies were not correlated with their degree of isolation. Factors that affected the biodiversity value of species include age, mode of origin, demographic history, and reproductive biology.  相似文献   

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Imanishi's "mental" (cerebral) view of speciation is presented, in Mizuhata's revision. The key concept here is the "ethological partition" of the species. Members of each species=society (etho-species) share the same mental (brain) software, irrespective of their genetic structure. Cerebral animals perform active programmed selection, not to be confused with passive, non-programmed "natural selection" as in Neo-Darwinism. The program includes mating-choice of peculiar characters, distinct from the Neo-Darwinian sexual selection supposed due to the specific choosy genes. Speciation can occur, as a "partition of species=society", with bifurcation of mate-choosing program in the parent species. A main promoter for this bifurcation is species-specific "passion" for especially significant characters: long necks, ornamental antlers, ocelli feathers, bright nuptial colors etc. The cichlids in Lake Victoria achieved explosive speciation, while retaining their genetic homogeneity completely. Therefore it is illogical to attribute this divergence to extraordinary mutations in "action controlling genes". The origin of species=society (etho-species) can trace along to the Cambrian Period.  相似文献   

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The first capture of the Greenland (or Black) halibut Reinhardtius hippoglossoides in the Arctic Ocean on the border with the East Siberian Sea (79°03′–79°08′ N 139°59′–141°16′ E, 259–277 m) and the repeated findings of the species in the Laptev Sea (78°03′–78°04′ N 132°56′–133°04′ E, 307 m; 78°33′–78°35′ N 138°44′–138°48′ E, 125 m) are reported. Fish (79 specimens with the length of 15.0–44.5 cm) were caught during four bottom trawlings on the edge of the continental shelf of the two seas in the transformed waters of Atlantic origin, as evidenced by the discovery of the indicator species of these waters—the Glacier lanternfish Benthosema glaciale (Myctophidae)—in one of the stomachs of halibut. The other captures of Greenland halibut in the Arctic were also reviewed.  相似文献   

19.
The amyloid peptide congener A beta(10--35)-NH(2) is simulated in an aqueous environment in both the wild type (WT) and E22Q "Dutch" mutant forms. The origin of the noted increase in deposition activity resulting from the Dutch mutation is investigated. Multiple nanosecond time scale molecular dynamics trajectories were performed and analyzed using a variety of measures of the peptide's average structure, hydration, conformational fluctuations, and dynamics. The results of the study support the conclusions that 1) the E22Q mutant and WT peptide are both stable in "collapsed coil" conformations consistent with the WT structure of, J. Struct. Biol. 130:130--141); 2) the E22Q peptide is more flexible in solution, supporting early claims that its equilibrium structural fluctuations are larger than those of the WT peptide; and 3) the local E22Q mutation leads to a change in the first solvation layer in the region of the peptide's "hydrophobic patch," resulting in a more hydrophobic solvation of the mutant peptide. The simulation results support the view that the noted increase in activity due to the Dutch mutation results from an enhancement of the desolvation process that is an essential step in the aggregation of the peptide.  相似文献   

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