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71.
Allozyme diversity and geographic variation in the widespread coastal sedge, Carex arenaria 总被引:1,自引:0,他引:1
Abstract. Allozyme electrophoresis was used to investigate the structure of genetic variation in the rhizomatous coastal sedge, Carex arenaria, throughout its European range — from the SW Iberian peninsula to the Baltic region. Material was sampled from 77 sites in five geographic regions. Nine of the 13 investigated loci were polymorphic in the total material and there were interregional differences in the number of polymorphic loci per site and the percentage of variable sites. In the Scandinavia/Baltic region only 61% of the sites contained at least one locus with more than one allele, whereas all the British and SW Iberian sites were variable. There was a general tendency for the regional frequencies of the less common alleles at individual loci to decline from SW to NE. The mean (over loci and sites) within‐site gene diversity (H site) was 0.064 (in calculations based on the number of observed multilocus allozyme genotypes within each sampling site). Although there was considerable variation between geographically adjacent sites, within‐site diversity showed a general decrease from SW to NE in Europe. There were significant differences in within‐region gene diversity (Hreg) for the four most variable loci between the five regions. Hreg generally decreased from SW to NE Europe and most loci showed the highest diversity in the SW Iberian peninsula and the Bay of Biscay regions. The mean (over loci) gene diversity in the total material (Htot) was 0.070 and the levels of diversity in Carex arenaria are substantially lower than is usual in rhizomatous sedges. The within‐site, between‐site and between‐regional components of the total diversity were 92.4%, 2.5% and 5.1%, respectively. The low levels of overall gene diversity in C. arenaria and the successive decrease in diversity from SW to NE are interpreted in terms of the species’ history of postglacial spread into northern Europe. Despite the overall northwards decrease in diversity, the widespread occurrence of less common alleles and the lack of regional deviations from Hardy–Weinberg genotype frequency expectations suggest that C. arenaria is not predominantly self‐fertilized. 相似文献
72.
Effects of cooling water discharge on the structure and dynamics of epilithic algal communities in the northern Baltic 总被引:1,自引:0,他引:1
The Forsmark Biotest Basin is a shallow coastal ecosystem that receives brackish cooling-water discharge from a nuclear power
plant. The effects of the discharge on epilithic algal communities were investigated by analysing samples taken every third
week throughout one year at 11 sites differentially affected by temperature and/or flow rate enhancement. Community variation
was summarized in a canonical correspondence analysis (CCA) of species abundances as a function of site and date. The temperature
increase favoured blue-green algae at the expense of red and brown algae. Blue-green algae were however abundant in summer
in stagnant water, whether heated or not, and some red and brown algae became abundant in winter in heated sites with flowing
water. Green algae and diatoms increased in biomass in the heated sites, but not in relative cover-abundance. The absence
of ice and snow cover at sites with heated and/or flowing water caused autumn species to persist into winter, because of the
higher light intensity (compared with natural conditions) and the absence of the mechanical abrasion by ice. The thermal discharge
lowered species diversity (Shannon-Weaver index) both in summer and winter at sites with flowing water, but not at sites with
quiescent or stagnant water. CCA showed alternate periods of stability and rapid change within the seasonal cycle. Individual
species were placed according to their optimum; red and brown algae in winter/spring, green algae in spring/summer, blue-green
algae in summer, and diatoms at various times. Exceptions to this pattern were species endo- or epiphytic on species of a
different group. Analysis of the effects of temperature, flow rate and ice cover on the seasonal pattern of particular species
showed that different species respond in individualistic ways to different combinations of these environmental variables. 相似文献
73.
Elke EM Brouwers Alwin DR Huitema Jos H Beijnen Jan HM Schellens 《BMC clinical pharmacology》2008,8(1):7
Background
The aim of this study was to evaluate long-term platinum retention in patients treated with cisplatin and oxaliplatin. 相似文献74.
75.
R L Prentice 《Journal of theoretical biology》1973,39(3):601-608
An experimental design involving randomly selected quadrats with areas in geometric progression is discussed. The procedure is suggested when the clustering habits of a plant or animal species ate unknown. Several models for the number of individuals per unit area are considered. Tests for these distributions versus random dispersal are given, along with techniques for estimating cluster area and number of individuals per cluster. Illustrations are included. 相似文献
76.
A medium for the detection of Lancefield Group D cocci in skimmed milk powder by measurement of conductivity changes 总被引:1,自引:0,他引:1
A selective medium for the detection of Lancefield Group D cocci in skimmed milk powder by conductivity measurements was developed and evaluated using the Bactometer M123 and Malthus 128H systems. This medium promoted large changes in conductance and capacitance. The calibration curve of detection times vs concentration of Lancefield Group D cocci showed a linear correlation coefficient of 0.93 and the method gave comparable results in both conductivity instruments. Naturally contaminated samples containing c. 103 cfu/g of Lancefield Group D cocci gave detection times within 16–18 h which was sufficiently rapid for the medium to be used for the routine screening of skimmed milk powder. 相似文献
77.
Goring DR Banks P Fallis L Baszczynski CL Beversdorf WD Rothstein SJ 《The Plant journal : for cell and molecular biology》1992,2(6):999-1003
We have previously described a developmentally regulated mRNA in maize that accumulates in mature embryos and is involved in a variety of stress responses in the plant. The sequence of the encoded 16 kDa protein (MA16) predicts that it is an RNA-binding protein, since it possesses a ribonucleoprotein consensus sequence-type RNA-binding domain (CS-RBD). To assess the predicted RNA binding property of the protein and as a starting point to characterize its function we have used ribohomopolymer-binding assays. Here we show that the MA16-encoded protein binds preferentially to uridine- and guanosine-rich RNAs. In light of these results a likely role for this protein in RNA metabolism during late embryogenesis and in the stress response is discussed. 相似文献
78.
Current phylogenetic tree reconstruction methods assume that there is a
single underlying tree topology for all sites along the sequence. The
presence of mosaic sequences due to recombination violates this assumption
and will cause phylogenetic methods to give misleading results due to the
imposition of a single tree topology on all sites. The detection of mosaic
sequences caused by recombination is therefore an important first step in
phylogenetic analysis. A graphical method for the detection of
recombination, based on the least squares method of phylogenetic
estimation, is presented here. This method locates putative recombination
breakpoints by moving a window along the sequence. The performance of the
method is assessed by simulation and by its application to a real data set.
相似文献
79.
80.
OBJECTIVE--To audit the outcome of pregnancies booked for confinement in a general practitioner maternity unit in a district general hospital. DESIGN--Retrospective review of case records. SETTING--General practitioner maternity unit in a district general hospital. PATIENTS--685 Women referred to a general practitioner unit in 1987. RESULTS--315 Nulliparous women and 330 multiparous women were booked for confinement; 202 women transferred to consultant care before delivery and a further 104 during labour or after delivery. Recognised risk factors, other than nulliparity, rarely predicted the need for transfer. Confinement in the general practitioner unit was associated with low intervention and good fetal outcomes. CONCLUSIONS--The general practitioner maternity unit provides a safe alternative for confinement in low risk pregnancies. High rates of transfer deny this facility to many women who desire confinement in a low technology environment. 相似文献