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41.
正台湾灰麝鼩(Crocidura tanakae)属于鼩形目(Soricomorpha)鼩鼱科(Soricidae),首次被Kuroda于1938描述,其模式产地在中国台湾台中市(Taichung)。随后一直被认为是灰麝鼩(Crocidura attenuata)的亚种或同物异名(Corbet and Hill,1992;Hutterer,1993;Fang et al.,1997;Motoka- 相似文献
42.
Veith M Lipscher E Oz M Kiefer A Baran I Polymeni RM Steinfartz S 《Molecular phylogenetics and evolution》2008,47(3):916-931
The urodelan genus Lyciasalamandra, which inhabits a relatively small area along the southern Turkish coast and some Aegean islands, provides an outstanding example of a diverse but phylogenetically unresolved taxon. Molecular trees contain a single basal polytomy that could be either soft or hard. We here use the information of nuclear (allozymes) and mitochondrial (fractions of the 16S rRNA and ATPase genes) datasets in combination with area relationships of lineages to resolve the phylogenetic relationships among Lyciasalamandra species in the absence of sufficient node support. We can show that neither random processes nor introgressive hybridization can be invoked to explain that the majority of pairs of sister taxa form geographically adjacent units and interpret that this pattern has been shaped by vicariant events. Topology discordance between mitochondrial and nuclear trees mainly refers to an affiliation of L. helverseni, a taxon restricted to the Karpathos archipelago, to the western-most and geographically proximate mainland taxon in the nuclear tree, while in the organelle tree it turns out to be the sister lineage to the geographically most distant eastern clade. As this discordance cannot be explained by long-branch attraction in either dataset we suppose that oversea dispersal may have accounted for a second colonization of the Karpathos archipelago. It may have initiated introgression and selection driven manifestation of alien eastern mitochondrial genomes on a western nuclear background. Our approach of testing for area relationships of sister taxa against the null hypothesis of random distribution of these taxa seems to be especially helpful in phylogenetic studies where traditional measures of phylogenetic branch support fail to reject the null hypothesis of a hard polytomy. 相似文献
43.
Neves E Lourenço A Silva AC Coutinho R Brito L 《Systematic and applied microbiology》2008,31(5):387-392
Multiplex-PCR (MPCR) serogrouping and pulsed-field gel electrophoresis (PFGE) subtyping analysis are currently used by several public and private laboratories for the characterization of Listeria monocytogenes. In this study a set of 80 L. monocytogenes isolates belonging to the twelve serovars was used to investigate (i) the typeability of the rare serovars, (ii) the ability of PFGE analysis with ApaI and AscI to differentiate serovars within MPCR serogroups and (iii) the association of molecular types with the specific source or geographical origin of the isolates. With the exception of three isolates (rare serovars 4a and 4c) that were not amenable to restriction with ApaI, all the other analyzed isolates were subtyped by both enzymes. PFGE discriminated the 80 isolates into 62 combined ApaI and AscI PFGE patterns (pulsotypes), but could not differentiate serovars within MPCR serogroups, in which isolates from different serovars displaying the same pulsotype were found. Clustering analysis suggests that for some pulsotypes grouping according to Portuguese origin or source can be suggested. On the other hand, some L. monocytogenes clones are widely distributed. Two pulsotypes from Portuguese human isolates were identical to the ones displayed by human outbreak clones in the UK and in the USA and Switzerland, respectively, although they were not temporally matched. Computer-assisted data analysis of large and diverse PFGE type databases will improve the correct interpretation of subtyping data in epidemiological studies and in tracing routes and sources of contamination in the food industry. 相似文献
44.
This study uses a geographical information system (GIS) and statistical analysis to look for patterns in referrals to a British
cancer genetics service. In this case, familial cancers are taken to be those that can develop when an individual inherits
DNA mutations that cause an increased risk of cancer. Between 1998 and 2006 the Cancer Genetics Service for Wales received
nearly 11,000 referrals for patients resident in Wales and it is the service database recording those referrals which is the
subject of this secondary analysis. Using postcodes to match referred patients to areas, deprivation scores were assigned.
Referral rates per 10,000 head of population across the 8-year study period by unitary authority are presented, as is information
on referrals from primary and secondary care sources by year. Each patient referred has their family history of cancer recorded
and is assigned to a risk category; high, medium or average. There are correlations between number of GPs (General Practitioners)
in a practice, number of patients referred from a practice, and deprivation as measured by the overall Welsh Index of Multiple
Deprivation 2005, such that the two former factors increase as deprivation decreases. Over time there were changes in referral
sources, with referrals from primary care overtaking those from secondary care in percentage and absolute terms. There were
also changes in the types of cancer referred, risk categories seen and to which centre referrals were made. Referral patterns
reveal an inverse relationship between deprivation and health service availability and use. 相似文献
45.
Black pepper is an important medicinal spice traded internationally. The extraction of high quality genomic DNA for PCR amplification
from dried black pepper is challenging because of the presence of the exceptionally large amount of oxidized polyphenolic
compounds, polysaccharides and other secondary metabolites. Here we report a modified hexadecyl trimethyl ammonium bromide
(CTAB) protocol by incorporating potassium acetate and a final PEG precipitation step to isolate PCR amplifiable genomic DNA
from dried and powdered berries of black pepper. The protocol has trade implication as it will help in the PCR characterization
of traded black peppers from different countries. 相似文献
46.
Spatial scan statistics with Bernoulli and Poisson models are commonly used for geographical disease surveillance and cluster detection. These models, suitable for count data, were not designed for data with continuous outcomes. We propose a spatial scan statistic based on an exponential model to handle either uncensored or censored continuous survival data. The power and sensitivity of the developed model are investigated through intensive simulations. The method performs well for different survival distribution functions including the exponential, gamma, and log-normal distributions. We also present a method to adjust the analysis for covariates. The cluster detection method is illustrated using survival data for men diagnosed with prostate cancer in Connecticut from 1984 to 1995. 相似文献
47.
48.
Aspergillus is a genus of mold fungi that includes more than 200 described species. Many members of the group are relevant pathogens and other species are economically important. Only one species has been analyzed for codon usage, and this was performed with a small number of genes. In this paper, we report the codon usage patterns of eight completely sequenced genomes which belong to this genus. The results suggest that selection for translational efficiency and accuracy are the major factors shaping codon usage in all of the species studied so far, and therefore they were active in the last common ancestor of the group. Composition and molecular distances analyses show that highly expressed genes evolve slower at synonymous sites. We identified a conserved core of translationally optimal codons and study the tRNA gene pool in each genome. We found that the great majority of preferred triplets match the respective cognate tRNA with more copies in the respective genome. We discuss the possible scenarios that can explain the observed differences among the species analyzed. Finally we highlight the biotechnological application of this research regarding heterologous protein expression. 相似文献
49.
Aim Local‐regional (LR) species diversity plots were conceived to assess the contribution of regional and local processes in shaping the patterns of biological diversity, but have been used also to explore the scaling of diversity in terms of its alpha, beta, and gamma components. Here we explore the idea that patterns in the geographical ranges of species over a continent can determine the shape of small region to large region (SRLR) plots, which are equivalent to LR plots when comparing the diversity of sites at two regional scales. Location To test that idea, we analysed the diversity patterns at two regional scales for the mammals of North America, defined as the mainland from Alaska and Canada to Panama. Method We developed a theoretical model relating average range size of species over a large‐scale region with its average regional point species diversity (RPD). Then, we generated a null model of expected SRLR plots based on theoretical predictions. Species diversities at two scales were modelled using linear and saturation functions for Type I and Type II SRLR relationships, respectively. We applied the models to the case of North American mammals by examining the regional diversity and the RPD for 21 large‐scale quadrats (with area equal to 160,000 km2), arranged along a latitudinal gradient. Results Our model showed that continental and large‐scale regional patterns of distribution of species can generate both types of SRLR relationship, and that these patterns can be reflected in LR plots without invoking any kind of local processes. We found that North American nonvolant mammals follow a Type I SRLR relationship, whereas bats follow a Type II pattern. This difference was linked to patterns in which species of the two mammalian groups distribute in geographical space. Conclusion Traditional LR plots and the new SRLR plots are useful tools in exploring the scaling of species diversity and in showing the relationship between distribution and diversity. Their usefulness in comparing the relative role of local and regional processes is, however, very limited. 相似文献
50.
Characteristics and conservation priority of threatened plants in the Yangtze valley 总被引:1,自引:0,他引:1
Z. Xie 《Biodiversity and Conservation》2003,12(1):65-72
One hundred and twenty-seven threatened species listed in the ChinaPlant Red Data Book were found in the Yangtze valley. One-third of them belongedto four families with high economic value, including Pinaceae, Magnoliaceae,Lauraceae and Ranuculaceae. Of all the plants, 66.9% grew in forests and 71.7%were threatened with damage to habitats. The threatened plants in the studiedregion formed a geographical pattern with two large and six small distributioncenters. The two large centers were in the high mountains in western Sichuan andnorthern Yunnan or around the Sichuan Basin. The six small centers were situatedin fragmented montane forests in the eastern part of the Yangtze valley. Todetermine a plant's threat category, the number of populations 10 wasused as the basic criterion as accorded with the China Plant Red Data Book. Thethreatened plants in the valley could be divided into five ranks of priority forconservation. The plants in the first rank comprised eight species endemic tothe valley, with only one population, which should be first preserved. It wasconcluded that human activity was the main factor threatening the survival ofplants, and protecting forests had been the most effective approach in savingthe threatened plants in the valley. 相似文献