Selenastraceae (Sphaeropleales, Chlorophyceae): rbcL, 18S rDNA and ITS-2 secondary structure enlightens traditional taxonomy, with description of two new genera, Messastrum gen. nov. and Curvastrum gen. nov.

The phylogeny of the family Selenastraceae was investigated by light microscopy, 18S rDNA, rbcL and ITS-2 analyses. Various morphological features traditionally used for species and genera identification were investigated. All selenastracean strains studied have naked pyrenoids within the chloroplast, except the genus Chlorolobion, which presented starch envelope. The molecular analyses showed that no morphological criterion considered so far is significant for the systematics of the Selenastraceae, but a set of features may be suitable to identify the genera Ankistrodesmus and Chlorolobion. Phylogenetic analyses showed the genera Monoraphidium, Kirchneriella and Selenastrum were not monophyletic and not distinguishable as separate genera. The polyphyly of the genus Selenastrum led to the description of two new genera, Curvastrum gen. nov and Messastrum gen. nov.