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.     

Enantiomer fractions of chiral organochlorine pesticides and polychlorinated biphenyls in standard and certified reference materials

Enantiomeric ratios (ERs) and enantiomeric fractions (EFs) of a number of chiral organochlorine pesticides and PCB atropisomers were measured by chiral gas chromatography/mass spectrometry (GC/MS) in five standard (SRM) and certified (CRM) reference materials: SRM 1588a (organics in cod liver oil), SRM 1945 (organics in whale blubber), Marine Mammal Quality Assurance Exercise Control Material IV (NIST IV, organics in whale blubber), CRM trout, and CRM EC-5 (sediment). Target analytes were cis- and trans-chlordane, heptachlor exo-epoxide, oxychlordane, U82, MC5, MC6, MC7, o,p^′-DDT, and PCB congeners 91, 95, 136, 149, 174, 176, and 183. Measured ERs and EFs are in close agreement with the few literature values reported for some of these analytes in SRMs and CRMs. Chiral PCB ERs and EFs measured by one-dimensional chiral GC/MS were similar to values measured using multidimensional chiral GC/MS. Non-racemic chiral compositions are in agreement with known uptake and biotransformation in the respective environmental matrices. These values should aid in the quality assurance/quality control methodologies for chiral environmental chemistry using standardized reference materials.     

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).     

Nonindigenous biota on artificial structures: could habitat creation facilitate biological invasions?

We identified different distributions of marine nonindigenous species (NIS) and native species on some artificial structures versus natural reefs and using experimental manipulations, revealed some possible causal mechanisms. In well-established subtidal assemblages, numbers of NIS were 1.5–2.5 times greater on pontoons or pilings than on rocky reefs, despite the local species pool of natives being up to 2.5 times greater than that of NIS. Conversely, on reefs and seawalls, numbers of native species were up to three times greater than numbers of NIS. Differential recruitment to different positions and types of surfaces appeared to influence distribution patterns. NIS recruited well to most surfaces, particularly concrete surfaces near the surface of the water, whilst natives occurred infrequently on wooden surfaces. The position of rocky reefs and seawalls close to the shore and to the seabed appeared to make them favourable for the recruitment of natives, but this positioning alone does not hinder the recruitment of NIS. We argue that pontoons and pilings represent beachheads (i.e. entry points for invasion) for many nonindigenous epibiota and so enhance the spread and establishment of NIS in estuaries. Habitat creation in estuaries may, therefore, be a serious threat to native biodiversity. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

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.     

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.     

大气腐蚀试验标准中相对湿度和温度控制的考虑

<正>在本文中,我们将讨论操作腐蚀试验箱的实验室工程师和研究员提出的众多问题:如何测量和控制这些试验箱中的相对湿度和温度。腐蚀试验标准中对相对湿度测量和控制的描述不具体,甚至某些时候是错误的,导致试验者产生了很大的困惑。设备制造商已经使用了各种各样的测量技术,每种测量技术代表对标准的一种合理解释,但是它们相互之间产生的结果不尽相同。除了这些困惑外,对相对湿度控制的需求和人们所期望的现代测试标准同样不明确。最后,实验室条件