Diffusion of obsidian in the Mediterranean basin: a trace element characterization of obsidian from Sardinia (Italy) by Instrumental Neutron Activation Analysis

Obsidian samples from Monte Arci in Sardinia (Italy) have been characterized by their minor and trace element concentration in order to find discriminating parameters useful to provenance the prime matter of obsidian artifacts. Obsidian samples were collected both at the SA, SB and SC outcrops and far away from them. All samples were submitted to INAA. The trace element concentration appears to be very useful to discriminate the three flows. Multivariate statistical analysis confirms the satisfactory distinction between the three sources. The assignment of the samples collected far away from outcrops to a specific flow (SC) validates the hypothesis that obsidian blocks might have been washed out by alluvial events

Phylogenetic relationships among the Mediterranean Alexandrium (Dinophyceae) species based on sequences of 5.8S gene and internal transcribed spacers of the rRNA operon.

A phylogenetic analysis of the genus Alexandrium, including both the most common and rare species from coastal areas of the Mediterranean Sea was carried out. Nucleotide sequences of 5.8 S gene and Internal Transcribed Spacer regions of the rRNA operon were examined and analysed together with isolates of Alexandrium spp. from elsewhere in the world. These rDNA ribosomal markers were useful in delineating the phylogenetic position of species in the genus, as well as in determining relationships among isolates within each species collected from different localities. Results of phylogeographical analyses within the 'Alexandrium tamarense' species complex identified three lineages in the Mediterranean Sea: the Mediterranean (ME), Western European (WE) and Temperate Asian (TA) clades. The phylogenetic grouping of the isolates is consistent with the ribotype clades, but not with the morpho-species that constitute the complex. Additional non-toxic isolates were included in the ME clade. The NA (North Atlantic) clade is the fourth group within the 'Alexandrium tamarense' species complex identified by phylogenetic analyses. Based on its higher genetic diversity and phylogeographical relationships, it can be hypothesized that the NA clade represents the ancestral group of the 'Alexandrium tamarense' species complex. Alexandrium minutum isolates of the NW Mediterranean clustered with strains from Brittany and Australia. Alexandrium minutum constituted a sister clade of A. tamutum, which is another species strongly associated with the Mediterranean area. Another typical Mediterranean species, A. taylori, was placed as a sister clade of A. pseudogoniaulax by the phylogenetic analysis. Finally, the phylogenetic relationships of some Alexandrium morpho-species that were infrequently observed in the Mediterranean Sea have been resolved

Resting cysts of the toxigenic dinoflagellate genus Alexandrium in recent sediments from the Western Mediterranean coast, including the first description of cysts of A. kutnerae and A. peruvianum

Publicado