Combined Morphological and Molecular Phylogenetic Analysis of the Genus Tripos (Dinophyceae) from the Persian Gulf

The genus Tripos (the marine Ceratium) often comprises a major part of micro-phytoplankton in terms of abundance and diversity that plays an important role in annual primary production; however, it has received little attention in the Persian Gulf. The morphology and phylogeny of Tripos furca, T. massiliense, and T. concilians were investigated in the present research. Samples collected from the Persian Gulf were identified morphologically under an inverted microscope, and the SSU rDNA sequence from individual cells was amplified using a polymerase chain reaction. The SSU rDNA sequence was determined for Iranian strains of these species and registered in the GenBank. The results of the phylogenetic analysis indicated the formation of a monophyletic clade of the family Ceratiaceae with high support. In this clade, freshwater species of Ceratium were grouped in a highly supported subclade, and marine species comprised another subclade. These results well demonstrated the separation (divergence) of marine and freshwater species of Ceratium. Altogether, the present results agree with previous studies where a considerable evolutionary distance is suggested for marine and freshwater species and support the formation of two highly distinct monophyletic clades based on SSU rDNA and LSU rDNA fragments and the number of cingular plates.