The molecular methods must be evidently preferred in this work, but other approaches (biochemical, ecophysiological, ecological, morphological) must be included into the final evaluation.
When you refer to the Synechococcus, it is important to specify, which clade you have in mind. Honda et al. (1999) and Roberston et al. (2001) showed Synechococcus is polyphyletic genus composed of a least 5 lineages. There are more recent works showing even more clades. From an amount of sequences and relationship to Prochlorococcus, I can assume, it is a marine pelagial picoplanktic clade. However, it should be specified for unexperienced reader in the field of cyanobacteria. The other polyphyletic genera should be also specified—Phormidium, Leptolyngbya, Microcoleus and others. Moreover, although the sequences might have same name (i.e., Synechococcus), they belong to polyphyletic groups, thus they probably belong to different genera, which have not yet been described.