The purpose of this study was to determine the phylogeographic structure of the brackish-hypersaline cyprinodont fish Aphanius fasciatus (Valenciennes, 1821), using sequencing and RFLP analysis of a 1,330 bp mitochondrial DNA segment containing part of the 16S
rRNA gene as well as the genes for tRNA-Leu, NADH subunit 1 and tRNA-Ile. Individuals were collected from 13 different sites
in Greece and Turkey, while seven published A. fasciatus sequences were also included to cover the area of distribution of the species. Pairwise sequence divergence values ranged
from 0 to 4.51%. Congruent phylogenies were recovered with maximum likelihood, maximum parsimony and neighbour-joining methods.
All analyses revealed two main groups. The first group consists of populations from almost all localities that drain into
the Aegean Sea. The second group comprises the remaining population samples, which in some cases seem to consist of population-specific
subgroups. Our results show that vicariant events have predominantly affected the evolution of A. fasciatus, with the Messinian salinity crisis having shaped the present genetic structure of its populations. Additionally, the life-history
traits of the species, which determine a low potential for dispersal, coupled with the typical fragmentation of brackish-hypersaline
water habitats have led to a high degree of isolation of A. fasciatus populations, even at restricted spatial scales. Analysis of the partitioning of the total amount of polymorphism with analyses
of molecular variance (AMOVA) gave a value of FST = 84.6%. Potential conservation policies concerning A. fasciatus should also consider the low-genetic variability in the majority of its populations and the presence of fixed haplotypes
in some of them. 相似文献
Salmonids are known for the occurrence in sympatry of two life-history forms, one that undergoes migration to sea before returning
to freshwater to reproduce (anadromous) and one that inhabits freshwater without a migration phase (resident). Whereas one
breeding population is often suggested by population genetic studies, mating patterns have rarely been directly assessed,
especially when both sexes are found within each life-history form. By using highly polymorphic microsatellite loci and parentage
analysis in a natural population of sympatric anadromous and resident brook charr (Salvelinus fontinalis), we found that gene flow occurred between the two forms and was mediated by resident males mating with both resident and
anadromous females. Determinants of reproductive success, estimated by the number of surviving juveniles (ages 1 and 2 years),
differed between the sexes. No strong evidence of the influence of size on individual reproductive success was found for males,
whereas larger females (and hence most likely to be anadromous) were more successful. The higher individual reproductive success
of anadromous fish compared to residents was mainly explained by this higher reproductive success of anadromous females. We
suggest that resident males adopt a “sneaking” reproductive tactic as a way of increasing their reproductive success by mating
with females of all sizes in all habitats. The persistence of the resident tactic among females may be linked to their advantage
in accessing spatially constrained spawning areas in small tributary streams unavailable to larger females. 相似文献
Ninety-six women of advanced maternal age were interviewed about the way they obtained information on prenatal diagnosis and about how the decision was made as to what procedure was to be performed (transabdominal chorionic villus sampling (TA-CVS) or amnio-centesis). In the CVS group, women visited their physician or midwife earlier in pregnancy (mean 7.1 weeks) than those in the amniocentesis group (mean 10.7 weeks). The availability of prenatal diagnosis was not mentioned during the first antenatal visit in 55 per cent of women from the amniocentesis group as opposed to 25 per cent from the TA-CVS group. Approximately 40 per cent of women eligible for prenatal diagnosis did not receive any information from the referring body prior to counselling at our centre. Only 29 per cent of women who underwent amniocentesis had actually chosen this procedure; 71 per cent were too late to undergo TA-CVS at 12 weeks. It is concluded that information to the patient must be improved in order to ensure early referral for prenatal diagnosis. 相似文献
The concentrations and profiles of dibenzo-p-dioxins, dibenzofurans, polychlorinated biphenyls and polynuclear aromatic compounds in various environmental matrices are presented in this study. The examined environmental matrices are total suspended particles, fly ash and soil collected in NW Greece, an area characterized by intensive coal burning for electrical power generation. Moreover, the occurrence of organic micropollutants in soot after an accidental fire was examined and the possible impact on the outdoor environment was evaluated. Results were statistically treated to obtain information on representative PCDD/F profiles in each matrix and to compare these profiles with the compositional patterns of possible sources from literature. Coal combustion, fly ash and vehicle exhausts appeared to be the most possible sources in local atmosphere. 相似文献
Field studies monitoring pesticide pollution in the Morvan region (France) have revealed surface water contamination by some herbicides. The purpose of this study was to investigate in greater detail the transport of two herbicides, used in Christmas tree production in the Morvan, under controlled laboratory conditions. Thus, the leaching of hexazinone (3-cyclohexyl-6-dimethyl-amino-1-methyl-1,3,5-triazine-2,4 (1H,3H) dione) and glyphosate (N-(phosphono-methyl-glycine)) through structured soil columns was studied using one loamy sand and two sandy loams from sites currently under Christmas tree cultivation in the Morvan. The three soils were cultivated sandy brunisol [Sound reference base for soils, D. Baize, M.C. Girard (Coord.), INRA, Versailles, 1998, 322 p] or, according to the FAO [FAO, World reference base for soil resources, ISSS-ISRIC-FAO, FAO, Rome, Italy, 1998], the La Garenne was an arenosol and the two other soils were cambisols. The clay contents of the soils ranged from 86 to 156 g kg(-1) and the organic carbon ranged from 98 to 347 g kg(-1). After 160 mm of simulated rainfall applied over 12 days, 2-11% of the applied hexazinone was recovered in the leachate. The recovery was much higher than that of glyphosate, which was less than 0.01%. The greater mobility of hexazinone might be related to its much lower adsorption coefficient, K(oc), 19-300 l kg(-1), compared with 8.5-10231 l kg(-1) for glyphosate (literature values). Another factor that may explain the higher amounts of hexazinone recovered in the leachates of the three soil columns is its greater persistence (19.7-91 days) relative to that of glyphosate (7.9-14.4 days). The mobility of both herbicides was greater in the soils with higher gravel contents, coarser textures, and lower organic carbon contents. Moreover, glyphosate migration seems negatively correlated not only to soil organic carbon, but also to aluminium and iron contents of soils. This soil column study suggests that at the watershed scale, surface water contamination by hexazinone could occur via the horizontal subsurface flow in upper centimeters of soil. In contrast, the surface water contamination with glyphosate by this mechanism appears unlikely. 相似文献
The desorption kinetics of in situ chlorobenzenes (dichlorobenzenes, pentachlorobenzene and hexachlorobenzene) and 2,4,4′-trichlorobiphenyl (PCB-28) were measured with a gas-purge technique for river Rhine suspended matter sampled in Lobith, The Netherlands. This suspended matter is the main source of sediment accumulation in lake Ketelmeer. In lake Ketelmeer sediment earlier observations showed that slow and very slow fractions dominate the desorption profile.
For the river Rhine suspended matter, only for PCB-28 a fast desorbing fraction of around 1.6% could be detected. The observed rate constants were on the average 0.2 h−1 for fast desorption, 0.004 h−1 for slow desorption, and 0.00022 h−1 for very slow desorption. These values are in agreement with previous findings for the sediment from lake Ketelmeer and with available literature data on fast, slow, and very slow desorption kinetics.
The results from this study show the similarity of desorption profiles between river Rhine suspended matter, and the top layer sediment from lake Ketelmeer. This indicates that slow and very slow fractions are already present in material forming the top layer of lake Ketelmeer, and were not formed after deposition of this material in the lake. The absence of detectable fast fractions for most compounds could be caused by the absence of recent pollution of the suspended matter. But, the observations may also be explained by a rapid disappearance of compounds from the fast fraction due to a combination of a high affinity of very slow sites for these compounds, and their relatively high volatility. 相似文献
In an in vivo/in vitro assay system (Massa et al., 1990) we have detected the carcinogenic activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The carcinogenic potential measured in this system is concentration-dependent. Experiments with other carcinogenic compounds have revealed that TCDD at low doses can act as co-carcinogen. At higher concentrations TCDD induces TNF-α production. 相似文献