Morphology and phylogeny of three planktonic Radiococcaceae sensu lato species (Sphaeropleales, Chlorophyceae) from China, including the description of a new species Planktosphaeria hubeiensis sp. nov.

The family Radiococcaceae sensu lato, defined as colonial autospore-producing mucilaginous coccoid green algae, is widespread in terrestrial and freshwater habitats. Three species of Radiococcaceae sensu lato, including two Radiococcus species and one Planktosphaeria species, were described from China by light and electron microscopy. A new species of Planktosphaeria, Planktosphaeria hubeiensis sp. nov. was erected based on morphological comparisons and genetic analyses. Our phylogenetic analyses indicated that Radiococcaceae sensu lato is polyphyletic, and separated into three lineages. The Radiococcus species did not cluster into a monophyletic group in phylogenetic analyses; therefore the taxonomy of the genus Radiococcus should be revised in the future.