We agree that this might be confusing to the reader. We have therefore clarified this choice and added this part to the first M&M section and the literature suggested has been cited: “Sequences termed Synechococcus on the other hand were analysed together with sequences of Prochlorococcus, since Synechococcus is known to be a polyphyletic group and if all sequences (including a minimum of five lineages [36–38]) are taken together, Prochlorococcus has to be included too.”
Of course, the complex of all these methods must be corrected with the progress of science, and especially for cyanobacteria is necessary to apply the so called “polyphasic approach” for their classification.