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.     

Airborne lead in the Springfield, Missouri, area during a 19-year period (1975-1993)

Concentrations of airborne lead at Springfield, Missouri, in 1975-1993 have been determined by analysis of particulate material collected on glass-fiber filters during the 19-year period. Nitric acid-soluble lead in 1100 samples collected at a total of 19 monitoring stations was determined by atomic absorption spectroscopy and by differential pulse polarography. Ambient concentrations of airborne lead were found to decrease steadily (by more than 90%) during this period in spite of increases in area population and in automobile traffic. The decrease is significantly correlated with national trends in total emissions of lead to the atmosphere and with US ambient lead levels. Airborne lead from a coal-fired power plant was small compared with that from gasoline burning.     

Continuous monitoring of ultrafine,fine, and coarse particles in a residence for 18 months in 1999-2000

Continuous monitors were employed for 18 months in an occupied townhouse to measure ultrafine, fine, and coarse particles; air change rates; wind speed and direction; temperature; and relative humidity (RH). A main objective was to document short-term and long-term variation in indoor air concentrations of size-resolved particles (0.01-20 microm) caused by (1) diumal and seasonal variation of outdoor air concentrations and meteorological variables, (2) indoor sources such as cooking and using candles, and (3) activities affecting air change rates such as opening windows and using fans. A second objective was to test and compare available instruments for their suitability in providing real-time estimates of particle levels and ancillary variables. Despite different measuring principles, the instruments employed in this study agreed reasonably well for particles less than 10 microm in diameter. The three instruments measuring fine and coarse particles (aerodynamic diameter between 0.3 and 20 microm) agreed to within 30% in their overall estimates of total volume. Two of these instruments employed optical scattering, and the third used an aerodynamic acceleration principle. However, several lines of evidence indicated that the instrument employing aerodynamic acceleration overestimated concentrations for particle diameters greater than 10 microm. A fourth instrument measuring ultrafine and accumulation-mode particles (0.01-1 microm) was operated with two different inlets providing somewhat different particle size ranges. The two inlets agreed in the ultrafine region (< 0.1 microm) but diverged increasingly for larger particles (up to 0.445 microm). Indoor sources affecting ultrafine particle concentrations were observed 22% of the time, and sources affecting fine and coarse particle concentrations were observed 12 and 15% of the time, respectively. When an indoor source was operating, particle concentrations for different sizes ranged from 2 to 20 times the average concentrations when no indoor source was apparent. Indoor sources, such as cooking with natural gas, and simple physical activities, such as walking, accounted for a majority (50-90%) of the ultrafine and coarse particle concentrations, whereas outdoor sources were more important for accumulation-mode particles between 0.1 and 1 microm in diameter. Averaged for the entire year and including no periods when indoor sources were apparent, the number distribution was bimodal, with a peak at approximately 10 nm (possibly smaller), a shallow minimum at approximately 14 nm, and a second broad peak at approximately 68 nm. The volume distribution was also bimodal, with a broad peak at approximately 200 nm, a minimum at approximately 1.2 microm, and then an upward slope again through the remaining size fractions. A database was created on a 5-min averaging time basis. It contains more than 90,000 measurements by two of the instruments and approximately 30,000 by the two optical scattering instruments. About 4500 hour-long average air change rates were also calculated throughout the year using a dedicated gas chromatograph with electron capture detection (GC/ECD). At high air change rates [> 0.8 air changes per hour (hr(-1))], particle concentrations were either elevated (when no source was present) or depressed (when an indoor source was operating) by factors of up to 2 compared with low air change rates.     

Expect Déjà vu all over again

It is difficult to define “property damage,” but one knows it when one sees it. Groundwater and soil impacts are readily discernible. However, owners of property that has been adversely affected by environmental conditions caused by others have recently sought recovery for the stigma which may attach to property which has in the past been affected by hazardous substances, even after remediation. These cases are particularly interesting in light of the traditional causes of action for negligence, trespass, and nuisance, and the statutes of limitations which may affect both rights to sue and damages. This article addresses “stigma” as an emerging area and an element of damages in environmental cases.     

Design,management, and key accomplishments of a coordinated environmental research program on acidic deposition

The present and potential adverse effects of the atmospheric input of acidic and acidifying substances on the environment have been of significant public and scientific concern for the past several decades. This article describes the background, design, implementation, and major accomplishments of a 6-yr integrated multidisciplinary environmental research program designed to address the issue of the regional scale consequences of acidic deposition on the environment and human health in Alberta. The research program was called the Acid Deposition Research Program (ADRP) and was a cooperative undertaking between industry, the Energy Resources Conservation Board, and the government of Alberta, Canada. The research effort was designed and guided by two external science advisory boards, biophysical and human health, to maintain objectivity and continuity from beginning to end. Public input was sought, encouraged, and ensured by a public advisory board. The major conclusions of the ADRP are presented as well as observations on the needs of future integrated multidisciplinary research programs.     

Falls from buildings and other fixed structures in New Zealand

Epidemiologic studies of falls from buildings and other fixed structures have historically focused on the urban environment. In this study, national injury mortality and hospitalisation data, supplemented by Coroner's investigation reports, were used to describe the epidemiology of such falls across an entire nation, New Zealand. The overall death rate was 0.30 per 100,000 persons per year. Ninety-three percent of cases were older than 14 years of age. Sixty-nine percent of falls were from buildings, with 31% from other structures. Sixty-seven percent of fatal falls were from a height of 10 meters or less. The incidence rate of hospitalisations was 21.4, with the highest rates among those aged 0–9. Fifty-five percent of non-fatal falls were from buildings, with 45% from other structures. National measures to prevent falls from structures should extend to a wide variety of structures and environments. Data presented on the age distributions of falls from different types of structures and structural components (windows, etc.) provide indicators for fall prevention.     

Protection from wintertime rainfall reduces nutrient losses and greenhouse gas emissions during the decomposition of poultry and horse manure-based amendments

Manure-based soil amendments (herein “amendments”) are important fertility sources, but differences among amendment types and management can significantly affect their nutrient value and environmental impacts. A 6-month in situ decomposition experiment was conducted to determine how protection from wintertime rainfall affected nutrient losses and greenhouse gas (GHG) emissions in poultry (broiler chicken and turkey) and horse amendments. Changes in total nutrient concentration were measured every 3 months, changes in ammonium (NH₄⁺) and nitrate (NO₃^?) concentrations every month, and GHG emissions of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) every 7–14 days. Poultry amendments maintained higher nutrient concentrations (except for K), higher emissions of CO₂ and N₂O, and lower CH₄ emissions than horse amendments. Exposing amendments to rainfall increased total N and NH₄⁺ losses in poultry amendments, P losses in turkey and horse amendments, and K losses and cumulative N₂O emissions for all amendments. However, it did not affect CO₂ or CH₄ emissions. Overall, rainfall exposure would decrease total N inputs by 37% (horse), 59% (broiler chicken), or 74% (turkey) for a given application rate (wet weight basis) after 6 months of decomposition, with similar losses for NH₄⁺ (69–96%), P (41–73%), and K (91–97%). This study confirms the benefits of facilities protected from rainfall to reduce nutrient losses and GHG emissions during amendment decomposition.

Implications: The impact of rainfall protection on nutrient losses and GHG emissions was monitored during the decomposition of broiler chicken, turkey, and horse manure-based soil amendments. Amendments exposed to rainfall had large ammonium and potassium losses, resulting in a 37–74% decrease in N inputs when compared with amendments protected from rainfall. Nitrous oxide emissions were also higher with rainfall exposure, although it had no effect on carbon dioxide and methane emissions. Overall, this work highlights the benefits of rainfall protection during amendment decomposition to reduce nutrient losses and GHG emissions.     

Setbacks to shoot growth are common in woody plants, so how are shoots of some species safer than others?

Tissue turnover is a critical facet of plant life history variation. This study quantifies losses from setbacks to growth of terminal woody shoots 1.2m long, across 83 species and seven sites in eastern Australia. Setbacks, where the leading meristem had been removed or died and a new leader had emerged, were common (median three per shoot). Shoots had lost an average of 0.25 m of lead-stem length for 1.2 m net shoot-length gain. Insects like girdlers and borers were prominent causes of large setbacks. The sites spanned tropical to temperate and humid to semiarid climates, but variation in stem loss was much greater across species than across sites. We measured 17 plant functional traits related to growth form, mechanics, hydraulics, and economics. Only four traits were correlated with variation across species in stem losses: stem diameter, stem nitrogen content, bark thickness, and maximum photosynthetic rate. The correlations were weak. Stem specific gravity (wood density) showed no correlation with risk. Our results suggest a pattern similar to the growth risk trade-off known for herbaceous plants, where traits associated with fast growth increase tissue turnover and herbivory, but the weak correlations leave ample scope for other influences that remain to be identified.     

The response of encrusting coralline algae to canopy loss: an independent test of predictions on an Antarctic coast

We assessed whether published observations of the ecology of encrusting coralline algae (Rhodophyta) from tropical and temperate coasts could be used to predict patterns and responses on a polar coast where such knowledge does not exist. On subtidal rocky coasts near Casey, East Antarctica, we detected a strong positive association of understorey encrusting coralline algae with canopies formed by the endemic alga Himantothallus grandifolius. The experimental removal of H. grandifolius caused corallines to bleach from red to pink/white concomitant with a decline in their photosynthetic activity. The magnitude of this decline (mean ± SE = 56.85±8.43%) was remarkably similar to that observed on temperate coasts (45.98±5.91%). Positive effects of nutrient enrichment of the surrounding water, hypothesized to alleviate the negative effects of canopy loss on encrusting corallines, were not detected. Removing H. grandifolius increased the intensity of photosynthetically active radiation and ultra-violet radiation reaching the substratum by three orders of magnitude, providing the basis for models invoking enhanced irradiance as the primary cause of the negative effects of canopy loss. Striking similarities among our results and those from tropical and temperate coasts suggest that responses of encrusting corallines to loss of canopies may have predictive properties across large distances and environmental gradients (tropical–temperate–polar).     

Skin lipids of the striped plateau lizard (<Emphasis Type="Italic">Sceloporus virgatus</Emphasis>) correlate with female receptivity and reproductive quality alongside visual ornaments

Sex pheromones can perform a variety of functions ranging from revealing the location of suitable mates to being honest signals of mate quality, and they are used in the mate selection process by many species of reptile. In this study, we determined whether the skin lipids of female striped plateau lizards (Sceloporus virgatus) can predict the reproductive quality of females, thereby having the potential to serve as pheromones. Using gas chromatography/mass spectrometry, we identified 17 compounds present in skin lipids of female lizards. Using principal component analysis to compare the skin lipid profile of receptive and non-receptive females, we determined that an uncharacterized compound may allow for chemical identification of receptive mates. We also compared extracted principal components to measures of female fitness and reproductive qualities and found that the level of two 18 carbon fatty acids present in a female’s skin lipids may indicate her clutch size. Finally, we compared the information content of the skin lipids to that of female-specific color ornaments to assess whether chemical and visual cues transmit different information or not. We found that the chroma of a female’s orange throat patch is also related to her clutch size, suggesting that chemical signals may reinforce the information communicated by visual ornamentation in this species which would support the “backup signals” hypothesis for multiple signals.