Genetic variability and differentiation in the Mediterranean endemic starry ray Raja asterias (Delaroche, 1809)

The present study deal with the population structure and connectivity of the Mediterranean endemic starry ray Raja asterias (Delaroche, 1809) in the Western and Eastern Mediterranean basin. A panel of eight microsatellite loci which cross-amplify in Rajidae (El Nagar, 2010) was used to assess population connectivity and structure. Those aims were investigated by analyzing the genetic variation of 9 population sample for a total of 185 individuals collected during past scientific surveys (MEDITS, GRUND), commercial trawling and also directly at fish markets. The purpose of this thesis is to estimate the genetic divergence occurring between the Mediterranean populations and, in particular, to assess the presence of any barrier (geographic, hydrogeological and biological) to gene flow for this species. Different statistical approaches were performed to reach this aim evaluating both the genetic diversity (nucleotide diversity, allelic richness, observed and expected heterozygosity and Hardy-Weinberg equilibrium test) and the population differentiation patterns (pairwise Fst estimated and population structure analysis). The results obtained from the analysis of the microsatellite dataset suggest a geographic and genetic separation between the starry ray populations of the Mediterranean basin into three or four distinct groups: Western and Eastern Mediterranean basins and Sicilian coast always clustering as an independent group and Algeria which could be or not considered another separate group. The data were discussed from both an evolutionary and a conservation point of view and in relation to previous results obtained by the analysis of mitochondrial marker. A comparison with other Mediterranean demersal skate species was performed in order to better contextualise our results. Finally, our results could offer useful information to protect vulnerable species as R. asterias and developing effective conservation plans in the Mediterranean.

»Imitation is the means, not the end, of art« - Peter Paul Rubens und Sir Joshua Reynolds über die Grammatik antiker Skulptur

In der vorliegenden Besprechung von Peter Paul Rubens’ Lehrschrift De imitatione statuarum (um 1610) und Sir Joshua Reynolds’ Discourse on Sculpture (1780) wird der Versuch unternommen, das Lehrgerüst der Grammatik als ein gemeinsames Referenzmodell herauszuarbeiten und die Position dieser beiden Malergrößen innerhalb der neuzeitlichen Kunsttheorie genauer zu verorten. Hierbei werden besonders die medienspezifischen Eigenschaften von Skulptur im Verhältnis zur Malerei diskutiert, die Maler bei der Nachahmung von antiker Skulptur zu beachten haben.

Ice Core Evidence for a Second Volcanic Eruption Around 1809 in the Northern Hemisphere

A volcanic signal observed in ice cores from both polar regions six years prior to Tambora is attributed to an unknown tropical eruption in 1809. Recovery of dacitic tephra from the 1809 horizon in a Yukon ice core ( Eclipse) that is chemically distinct from andesitic 1809 tephra found in Antarctic ice cores indicates a second eruption in the Northern Hemisphere at this time. Together with the similar magnitude and timing of the 1809 volcanic signal in the Arctic and Antarctic, this could suggest a large tropical eruption produced the sulfate and Antarctic tephra and a minor Northern Hemisphere eruption produced the Eclipse tephra. Nonetheless, the possibility that there were coincidental eruptions of similar magnitude in both hemispheres, rather than a single tropical eruption, should not be discounted. Correctly attributing the source of the 1809 volcanic signal has important implications for modeling the magnitude and latitudinal distribution of volcanic radiative forcing.