Molecular variation in Galdieria sulphuraria (Galdieri) Merola and its bearing on taxonomy

Cyanidium caldarium, Cyanidioschyzon merolae and Galdieria sulphuraria are three unicellular algae characteristic, of acid thermal environments. Recently, on the basis of morphological characters, three new species of Galdieria (G. partita, G. daedala, G. maxima ) isolated from acid-thermal springs in Russia have been instituted. A selected region of rbcL and the sequence of the intergenic spacer between the rbcL and rbcS have been amplified and sequenced from different Galdieria species and strains, in order to define molecular relationship among these interesting algae. The obtained cladogram shows that Cyanidium caldarium and Cyanidioschyzon merolae form a sister group which, in turn, is in a sister group relationship with Galdieria. This last genus is divided in two clades, one of which includes G. sulphuraria accessions from Naples (Italy), California, and Yellowstone and the other one includes G. sulphuraria accessions from Java (Indonesia) and from the Russian species. These results support the status of the genus Galdieria and suggest that G. daedala, G. maxima and G. partita are three very similar strains of G. sulphuraria; the rbcL variation within Galdieria accessions has a pattern which is broadly connected to the geographial distribution. The data obtained from the intergenic rbcL-rbcS spacer partly confirm those from the rbcL analysis.