The relationship between allele frequency and tidal height in a mussel hybrid zone: a test of the differential settlement hypothesis

The blue mussels Mytilus edulis L. and M. galloprovincialis Lmk. hybridize in western Europe. Within hybrid populations nuclear alleles specific to M. galloprovincialis increase in frequency with age and size. This relationship changes with tidal height; alleles from M. galloprovincialis occur more frequently high in the intertidal zone, while M. edulis alleles predominate in the low intertidal zone. We tested the hypotheses that larvae with M. galloprovincialis alleles tend to settle higher in the intertidal zone, or that mussels redistribute themselves with respect to tidal height after initial larval settlement. We sampled recently metamorphosed mussels every 2 weeks in a hybrid mussel population at Whitsand Bay in southwest England throughout the summer of 1996. We observed four cohorts of newly settled mussels. There was no evidence of differential settlement of mussels with different genotypes in connection with tidal height, or into shaded versus unshaded microsites. Therefore, we rejected the preferential settlement hypothesis. There was substantial movement of juvenile mussels in the first 4 weeks following initial settlement, but this “secondary settlement” did not result in genetic differentiation with respect to tidal height. Further, significant differences in allele frequencies were found between primary and secondary spat. This allele frequency change was in the opposite direction of that seen in the adult population, suggesting newly settled larvae may be experiencing different selective pressures than adults. We propose that the genetic structure of hybrid mussel populations with respect to tidal height is the consequence of differences in selection intensity. Received: 30 April 1999 / Accepted: 5 May 2000     

A framework for dependability engineering of critical computing systems

This paper presents a development model focused on the production of dependable systems. Three classes of processes are distinguished: (1) the system creation process which builds on the classical development steps (requirements, design, realization, integration); (2) dependability processes (i.e. fault prevention, fault tolerance, fault removal and fault forecasting); and (3) other supporting processes such as quality assurance and certification. The proposed approach relies on the identification of basic activities for the system creation process and for the dependability processes, and then on the analysis of the interactions among the activities of each process and with the other processes. Finally, to support the development of dependable systems, we define for each system creation activity, a checklist that specifies the key issues that need to be addressed with respect to each dependability process.     

Geographic variation in allele frequency of the gamete recognition protein M7 lysin throughout a mosaic blue mussel hybrid zone

Divergence at gamete recognition loci is hypothesized to result in speciation in broadcast spawning invertebrates. Many gamete recognition loci evolve quickly and show patterns of positive selection, yet the advantage of divergence is rarely known. M7 lysin is a sperm protein in the Mytilus edulis species complex that shows evidence of adaptive evolution. This locus is polymorphic with two distinct clades within Mytilus galloprovincialis, one of which, the D clade, shows the strongest signal of positive selection. We tested whether the geographic patterns in allele frequency were consistent with the hypothesis that positive selection on D clade alleles (G _D ) was due to reinforcement. Populations of M. edulis showed little evidence of introgression of G _D alleles, but there was no consistent evidence of reproductive character displacement. The lack of consistent patterns expected of reinforcement suggests that another mechanism is likely responsible for the adaptive divergence of M7 lysin.     

Combinatory chemical and biological approaches to investigate metal elements in agricultural runoff water

As part of a project studying the interactions between farming practices, soil erosion processes, and fate of agricultural pollutants into runoff waters, we conducted a pilot study to investigate the relationship between metal contents and metallothionein-2A (MT-2A) as a bioindicator of metal exposure. Runoff water samples were collected between May and November 1999 at the point of outlet of an elementary watershed located in the Paris basin. Selected metals (Al, As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn) were analyzed using conventional techniques. In parallel, human T cells were exposed to water samples for 6 and 18 h and then cell viability and MT-2A gene expression were measured. Results show that among the 10 water samples tested, Al and Zn predominate (highest values = 4.9 and 2.6 microM, respectively), while other metals were below the microM level. Five out of 10 samples induced MT-2A gene expression (30-80% increase at 18 h) as compared with the control. When comparing MT-2A induction profile with metals contents, no obvious correlation was found, suggesting that additional components or parameters are involved. Finally, there was an apparent inverse relationship between Ca concentration and MT-2A gene induction. Although still preliminary, in the absence of longer monitoring, this study shows that MT-2A gene expression is a useful tool to complement chemical analysis in assessing metal elements in water. These combinatory approaches will be pursued and integrated in an ongoing watershed field research project.     

Forest cover of insular Southeast Asia mapped from recent satellite images of coarse spatial resolution

The study provides an example of mapping tropical forest cover from SPOT-Vegetation satellite images of coarse spatial resolution (1 km) for the subregion of insular Southeast Asia. A satellite image mosaic has been generated from satellite images acquired for the period 1998 to 2000. Forest cover has been mapped by unsupervised digital classification. The mapping result has then been compared to selected forest maps from the subregion, demonstrating the potential to provide basic information on forest area extent and distribution, but also on massive forest cover change in the subregional context. Forest area estimates derived from the map for the subregion have been found comparable to those compiled by FAO. The results indicate that many of the remaining tropical forests in Southeast Asia, rich in timber resources and biodiversity, may be lost in the near future if deforestation continues at present or previous rates.     

Attitudes towards Recycling Household Waste in Exeter, Devon: quantitative and qualitative approaches

Recycling of household waste has become a very problematic area of British local government policy-making in which central government has set ambitious targets. Although local government can provide facilities for recycling, the attitudes of residents will be crucial if these targets are to be met. Accordingly, this paper outlines a framework for studying how households decide to recycle or not. The framework has been tested in Exeter in south-west England where a major survey found that respondents were much more likely to recycle if they had access to a structured kerbside recycling scheme. Many other factors influenced their attitudes and behaviours towards recycling, including their acceptance of the activity and their perception of the benefits and problems of recycling as a whole. The research uses the quantitative and qualitative data from the survey to demonstrate how individual attitudes can impact on recycling and how such research can yield useful data to enable policy-makers to adapt measures accordingly.     

An empirical perspective for understanding climate change impacts in Switzerland

Regional Environmental Change - Planning for the future requires a detailed understanding of how climate change affects a wide range of systems at spatial scales that are relevant to humans....     

Assessing alpine plant vulnerability to climate change: a modeling perspective

The potential ecological impact of ongoing climate change has been much discussed. High mountain ecosystems were identified early on as potentially very sensitive areas. Scenarios of upward species movement and vegetation shift are commonly discussed in the literature. Mountains being characteristically conic in shape, impact scenarios usually assume that a smaller surface area will be available as species move up. However, as the frequency distribution of additional physiographic factors (e.g., slope angle) changes with increasing elevation (e.g., with few gentle slopes available at higher elevation), species migrating upslope may encounter increasingly unsuitable conditions. As a result, many species could suffer severe reduction of their habitat surface, which could in turn affect patterns of biodiversity. In this paper, results from static plant distribution modeling are used to derive climate change impact scenarios in a high mountain environment. Models are adjusted with presence/absence of species. Environmental predictors used are: annual mean air temperature, slope, indices of topographic position, geology, rock cover, modeled permafrost and several indices of solar radiation and snow cover duration. Potential Habitat Distribution maps were drawn for 62 higher plant species, from which three separate climate change impact scenarios were derived. These scenarios show a great range of response, depending on the species and the degree of warming. Alpine species would be at greatest risk of local extinction, whereas species with a large elevation range would run the lowest risk. Limitations of the models and scenarios are further discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Speciation of five arsenic species (arsenite, arsenate, MMAAV, DMAAV and AsBet) in different kind of water by HPLC-ICP-MS

A method using Ion Chromatography hyphenated to an Inductively Coupled Plasma-Mass Spectrometer has been developed to accurately determine arsenite (As(III)), arsenate (As(V)), mono-methylarsonic acid (MMAA(V)), dimethylarsinic acid (DMAA(V)) and arsenobetaine (AsBet) in different water matrices. The developed method showed a high sensitivity with detection limits for each arsenic species close to 0.4pg injected. Arsenite and arsenate were the major species found in surface and well waters, but AsBet and DMAA(V) were found in some surface waters, which has never been reported before, while in some natural mineral waters located in volcanic region, the arsenic content exceeded the maximal admissible arsenic content by European legislation standards and the predominant form was As(V).