Diversity and species concept of the Vischeria/Eustigmatos complex (Eustigmatophyceae)

Vischeria and Eustigmatos are closely related genera occurring in terrestrial habitats. These genera were distinguished by the differences in the features of the cell wall (projections and ridges of different form, smooth surface respectively). Up to date three species of the genus Eustigmatos and twelve species of the genus Vischeria have been described, but nine of the Vischeria species have been rarely, if ever, observed since the original description. This work is focused on evaluating molecular variability, diversity, and taxonomy of the Vischeria/Eustigmatos complex. Ninety seven strains, obtained from public algal collections or newly isolated from localities from all over the world, were studied, including the type strains of two Eustigmatos species and three Vischeria species. Phylogenetic analyses of the ITS2 rDNA and rbcL sequences showed that these genera are not genetically separated. The five types strains each represented a separate evolutionary lineage. Some of the additional lineages included strains morphologically corresponding to the species Eustigmatos magnus. Some of the newly isolated strains are according to the markers examined genetically indistinguishable from known strains from public algal collections. However, some of them are new lineages. Only one of the phylogenetic..