Microscale genetic differentiation in a sessile invertebrate with cloned larvae: investigating the role of polyembryony

Microscale genetic differentiation of sessile organisms can arise from restricted dispersal of sexual propagules, leading to isolation by distance, or from localised cloning. Cyclostome bryozoans offer a possible combination of both: the localised transfer of spermatozoa between mates with limited dispersal of the resulting larvae, in association with the splitting of each sexually produced embryo into many clonal copies (polyembryony). We spatially sampled 157 colonies of Crisia denticulata from subtidal rock overhangs from one shore in Devon, England at a geographic scale of ca. 0.05 to 130 m plus a further 21 colonies from Pembrokeshire, Wales as an outgroup. Analysis of molecular variance (AMOVA) revealed that the majority (67%) of genetic variation was distributed among individuals within single rock overhangs, with only 16% of variation among different overhangs within each shore and 17% of variation between the ingroup and outgroup shores. Despite local genetic variation, pairwise genetic similarity analysed by spatial autocorrelation was greatest at the smallest inter-individual distance we tested (5 cm) and remained significant and positive across generally within-overhang comparisons (<4 m). Spatial autocorrelation and AMOVA analyses both indicated that patches of C. denticulata located on different rock overhangs tended to be genetically distinct, with the switch from positive to negative autocorrelation, which is often considered to be the distance within which individuals reproduce with their close relatives or the radius of a patch, occurring at the 4–8 m distance class. Rerunning analyses with twenty data sets that only included one individual of each multilocus genotype (n = 97) or the single data set that contained just the unique genotypes (n = 67) revealed that the presence of repeat genotypes had an impact on genetic structuring (PhiPT values were reduced when shared genotypes were removed from the dataset) but that it was not great and only statistically evident at distances between individuals of 1–2 m. Comparisons to a further 20 randomisations of the data set that were performed irrespective of genotype (n = 97) suggested that this conclusion is not an artefact of reduced sample size. A resampling procedure using kinship coefficients, implemented by the software package GENCLONE gave broadly similar results but the greater statistical power allowed small but significant impacts of repeat genotypes on genetic structure to be also detected at 0.125–0.5 and 4–16 m. Although we predict that a proportion of the repeat multilocus genotypes are shared by chance, such generally within-overhang distances may represent a common distance of cloned larval dispersal. These results suggests that closely situated potential mates include a significant proportion of the available genetic diversity within a population, making it unlikely that, as previously hypothesised, the potential disadvantage of producing clonal broods through polyembryony is offset by genetic uniformity within the mating neighbourhood. We also report an error in the published primer note of Craig et al. (Mol Ecol Notes 1:281–282, 2001): loci Cd5 and Cd6 appear to be the same microsatellite. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Biodegradation of linear alkylbenzene sulfonates in sulfate-leached soil mesocosms

Aromatic sulfonates (R-SO(3)(-)) can be used as sulfur sources by sulfate-starved bacteria in laboratory cultures and the corresponding phenols are excreted from the cells. The present study was conducted to demonstrate whether such desulfonation reactions also occur in sulfate-leached agricultural soil, where desulfonation of organic sulfur compounds may have agronomic importance as a S source for plants. Xenobiotic linear alkylbenzene sulfonates (LAS) were added to nominal concentrations of 0, 10 and 100 mgkg(-1) dry weight in a sandy soil that was depleted in sulfate by leaching the soil with water (sulfate depletion, approximately 75%). The soil was incubated at 20 degrees C in duplicate 3-dm(3) mesocosms for 8 weeks. Primary degradation of LAS was rapid with half-lives of 1-4 days. Sulfophenylcarboxylates were identified and quantified as intermediates, whereas linear alkylphenols (the expected primary desulfonation products) were not detected by high-pressure liquid chromatography coupled with both fluorescence and electrospray ionization-mass spectrometry. Thus, LAS was used by the bacteria as a source of energy and carbon, rather than as a source of sulfur. Measurements of soil pH, fluorescein diacetate (FDA) hydrolysis and arylsulfatase activity showed that stable microbial conditions prevailed in the soil mesocosms. FDA hydrolysis (a measure of total microbial activity) was transiently inhibited at the highest LAS concentrations. Arylsulfatase activity (i.e., hydrolysis of aromatic sulfate esters) was not significantly affected by the soil incubation, although arylsulfatases may be upregulated in sulfate-starved bacteria. However, an increased production of arylsulfatase may be difficult to detect due to the background of extracellular arylsulfatases stabilised in the soil. Therefore, the present data does not exclude a regulatory response to sulfate depletion by the soil microorganisms. However, the importance of desulfonation reactions in natural environments still needs to be demonstrated.     

Effects of environmental biomass-producing factors on Cd uptake in two Swedish ecotypes of Pinus sylvestris

A factorial design was used to study direct effects of external biomass-producing factors such as light, temperature and photoperiod on cadmium (Cd) uptake and indirect effects, via change in biomass production in two ecotypes of Scots pine (Pinus silvestris). The aim was to find out if the external factors affect the Cd uptake directly or via change in biomass production, and if the effect differs between ecotypes. Seedlings were grown under 10 combinations of external factors, i.e. temperature (15 and 20 degrees C), light intensity (50 and 200 micromol photons m(-2) S(-1)), photoperiod (18 h light/8 h darkness and continuous light) and external Cd concentration (totally 1.88 and 7.50 micromol). The treatment lasted for 18 days and Cd concentrations in roots and shoots were determined by AAS. The results showed that an increased biomass production increased the total Cd uptake but had a dilution effect on the Cd concentration, especially in the root tissues. The external factors tested did not have any direct effects on the Cd untake, only in the case of Cd translocation to the shoot did the higher temperature show a direct increase, but only in the southern ecotype. The two ecotypes reacted differently in Cd uptake and translocation to the external factors studied. The relative Cd uptake creased with increasing photoperiod in the northern but not in the southern ecotype. The southern ecotype decreased the Cd concentration in the shoot with increased light intensity caused by a dilution effect due to extensive shoot growth of this ecotype. The conclusion is that the uptake in pine seedlings is mainly regulated via biomass production, and not directly by light and temperature and that resulting plant Cd contents to a certain extent depend on plant origin.     

Altered menstrual cycles in women with a high dietary intake of persistent organochlorine compounds

Dietary exposure to persistent organochlorine compounds (POCs) has been found to affect the menstrual cycle in both animals and humans. In Sweden, the major exposure route for POCs is the consumption of fatty fish from the Baltic Sea. Thus, women who eat relatively large amounts of this fish constitute a suitable study group when investigating a possible association between dietary exposure to POC and menstrual cycle disruption. Questionnaires were sent to the exposed women, as well as to a socioeconomically similar cohort of controls, and information was collected on their menstrual cycles. Since the exposed women tended to smoke more than the controls, all results were adjusted for smoking habits. A cohort comparison found that the exposed women on average had 0.46 (95% confidence interval: 0.03, 0.89) days shorter menstrual cycles than controls. However, within the exposed cohort no effects were found of the proxy variables early life exposure and high consumption of Baltic Sea fatty fish. The results give some support to previous results from studies on women with similar exposure, but are not conclusive with respect to whether there is a causal association between POC exposure and menstrual cycle disruption.     

Partition coefficients of organic chemicals derived from reversed phase thin layer chromatography: Evaluation of methods and application on phosphate esters,polychlorinated paraffins and some PCB-substitutes

The application of reversed phase high performance thin layer chromatography has been evaluated for determination of octanol-water partition coefficients (P_oct) of organic chemicals. Best correlations between log P_oct and R_M-values were obtained on a C₁₈-bonded stationary phase using acetone-water or acetonitrile-water mixtures as eluting solvent. The latter mixture is preferred in work with high pressure liquid chromatography. A number of aryl and alkyl/aryl phosphate esters, polychlorinated paraffins and chemicals suggested as PCB-substitutes were chromatographed and the corresponding log P_oct-values calculated. Values for the phosphate esters corresponded reasonably well with previously reported data while data for other, often more complex compound mixtures (eg PCB-substitutes), need further evaluation. The use of the chromatographic system for screening purposes in work on environmentally significant data of possible organic pollutants is discussed.     

A one year study of the seasonal variations of sDDT and PCB levels in fish from heated and unheated areas near a nuclear power plant

An investigation of the influence of excess heat discharge from a nuclear power plant on the residual levels of the sDOT and PCB in roach and perch has been made during a period of one year. A seasonal variation of the residual concentrations was observed, with the highest levels during spring and early summer and lower more stable levels in the autumn. Significantly higher levels of the sDDT and PCB was observed in perch from the cooling water recipient as compared to values in perch from the intake area. No significant differences could however be verified for roach. The result stress the importance that, in a monitoring program, a sampling period with stable ecological conditions is selected.     

Responses to projected changes in climate and UV-B at the species level

Environmental manipulation experiments showed that species respond individualistically to each environmental-change variable. The greatest responses of plants were generally to nutrient, particularly nitrogen, addition. Summer warming experiments showed that woody plant responses were dominant and that mosses and lichens became less abundant. Responses to warming were controlled by moisture availability and snow cover. Many invertebrates increased population growth in response to summer warming, as long as desiccation was not induced. CO2 and UV-B enrichment experiments showed that plant and animal responses were small. However, some microorganisms and species of fungi were sensitive to increased UV-B and some intensive mutagenic actions could, perhaps, lead to unexpected epidemic outbreaks. Tundra soil heating, CO2 enrichment and amendment with mineral nutrients generally accelerated microbial activity. Algae are likely to dominate cyanobacteria in milder climates. Expected increases in winter freeze-thaw cycles leading to ice-crust formation are likely to severely reduce winter survival rate and disrupt the population dynamics of many terrestrial animals. A deeper snow cover is likely to restrict access to winter pastures by reindeer/caribou and their ability to flee from predators while any earlier onset of the snow-free period is likely to stimulate increased plant growth. Initial species responses to climate change might occur at the sub-species level: an Arctic plant or animal species with high genetic/racial diversity has proved an ability to adapt to different environmental conditions in the past and is likely to do so also in the future. Indigenous knowledge, air photographs, satellite images and monitoring show that changes in the distributions of some species are already occurring: Arctic vegetation is becoming more shrubby and more productive, there have been recent changes in the ranges of caribou, and "new" species of insects and birds previously associated with areas south of the treeline have been recorded. In contrast, almost all Arctic breeding bird species are declining and models predict further quite dramatic reductions of the populations of tundra birds due to warming. Species-climate response surface models predict potential future ranges of current Arctic species that are often markedly reduced and displaced northwards in response to warming. In contrast, invertebrates and microorganisms are very likely to quickly expand their ranges northwards into the Arctic.