Phylogenetic relationships among the Mediterranean Alexandrium (Dinophyceae) species based on sequences of 5.8S gene and Internal Transcript 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) c...