Single colony genetic analysis of epilithic stream algae of the genus Chamaesiphon spp.

In order to understand Chamaesiphon spp. evolution and ecological diversification, we investigated the phylogenetic differentiation of three morphospecies from field samples by means of single colony genetics. Individual colonies of three different morphospecies (C. starmachii, C. polonicus, C. geitleri,) were isolated from lotic gravel streams and their 16S rDNA nucleotide variability was analyzed. For a number of individual colonies, microscopical and ultrastructural analysis was also performed. A phylogenetic tree of all major lineages of the phylum of Cyanobacteria assigned all Chamaesiphon genotypes (1149–1176 bp) most closely with the family of Gomontiellaceae of the order Oscillatoriales. The sequences obtained from colonies assigned to C. starmachii (n = 21), C. polonicus (n = 9), and C. geitleri (n = 17) were found to reveal high average (3.5%) nucleotide diversity. No phylogenetic sub-branching in correspondence with morphology was observed suggesting that the three Chamaesiphon morphospecies did not represent monophyletic taxa. We could not attribute specific thylakoid ultrastructure to phylogenetic sub-branches; however, the observed parietally and loosely arranged thylakoids indicate that for the genus Chamaesiphon, the variability in thylakoid ultrastructure might have been underestimated. In summary, the high nucleotide diversity of the 16S rDNA gene implies phylogenetic diversity that corresponds little to morphological classification.