Geographical variation in shell shape of the pod razor shell Ensis siliqua (Bivalvia: Pharidae)

The present study assessed the existence of variation in the shell shape of the pod razor shell (Ensis siliqua) throughout its distributional range in the north- eastern Atlantic. Shells of E. siliqua caught at seven collecting sites (three in Portugal, three in Spain and one in Ireland) were studied by geometric morphometric methods, using both landmark- and contour-based methods. Both approaches (landmarks inside the valves and shell outline) discriminated the shells from Aveiro (centre of Portugal) and Strangford Lough (Ireland) from those caught in the nearby localities (remaining Portuguese and Spanish sites,maximum distance of 550 km by sea). Landmark analysis revealed that shells from Aveiro were more similar to shells from Ireland (*1,500 km far away). Contour anal- ysis revealed that shells from Aveiro had a shape with a comparatively larger height-to-width ratio, whereas shells from Ireland showed a slightly more curved outline than in the remaining sites. Landmark- and contour-based methods provided coherent complementary information, confirming the usefulness of geometric morphometric analyses for discerning differences in shell shape among populations of E. siliqua. A brief review of previous applications of geometric morphometric methods to modern bivalve spe- cies is also provided.The authors would like to thank Dr. Dai Roberts and Adele Cromie for providing samples of pod razor shells from Ireland. This study was funded by Community Initiative Programmes (INTERREG-IIIB, Atlantic Area) Sustainable HARvesting of Ensis (090–SHARE) and Towards Integrated Management of Ensis Stocks (206–TIMES) from the European Community. Marta M. Rufino and Paulo Vasconcelos benefited from postdoctoral grants (SFRH/BPD/14935/2004 and SFRH/BPD/26348/2006, respectively) awarded by the Fundação para a Ciência e Tecnologia (FCT—Portugal). Finally, the authors acknowledge three anonymous referees for valuable comments and suggestions that greatly improved the revised manuscript.publishe

A framework for robust estimation of beta using information fusion approach

WOS: 000444687500021In terms of financial management, the precise estimation of the beta of a financial asset is of vital importance. Beta is the measure of the relationship between the return of an asset or a portfolio and the market return and means the systematic risk within the scope of the Capital Asset Pricing Model. In general, it is known that the distribution of returns is significantly non-normal with thick-tail and skewness features. The ordinary least square (OLS) estimator that focuses on the centre of a distribution loses its effectiveness in such cases as the divergence of the distribution from normality, the presence of outliers, and heteroscedasticity. Quantile regression (QR), which is regarded as a non-parametric method, shows robustness against the specified phenomena. QR reveals the information carried by the distribution in tails as the returns focus on the whole of distribution. This means different beta for each percentile requiring investigation, and causes the problem of fusion of this information. Ordered Weighted Averaging (OWA) operators can merge the information coming from different percentiles at a required orness level depending on the attitude of the investor towards the risk. This study also suggests the use of OWA operators in addition to different quantile combination techniques used in the literature. As a result of the analysis performed based on Borsa Istanbul (Istanbul Stock Exchange) data, it was shown that OWA operators have a performance that is comparable to OLS and quantile combination techniques