Phylogenetic affinities of “Chantransia” stages in members of genus Virescentia (Batrachospermales, Rhodophyta)

The “Chantransia” is an asexual reproductive stage in the life history of freshwater red algal orders Batrachospermales and Thoreales. Due to the lack of diagnostic features, samples at this stage need to be combined with morphological comparison and molecular phylogenetic analysis to determine their taxonomic affinities. In this study, five bluish “Chantransia” isolates collected from Guangdong and Shanxi Provinces of China were detected as belonging to two species. Among them, isolates HT2001 and HT2103 are the “Chantransia” of Virescentia guangxiensis and have the following features: microscopic thalli, the erect system consisting of filaments with cylindrical cells, undifferentiated into proximal and distal parts, and relatively small monosporangia (< 20 µm in diameter). The three other isolates (GD231, GD233 and GD234), from Dinghu Mountain of Guangdong Province, are characterized by the following features: microscopic thalli with a well-developed prostrate system composed of creeping and loosely aggregated filaments, and the erect system consisting of filaments with cylindrical cells and small monosporangia (< 20 µm in diameter). Phylogenetic analyses based on rbcL and COI-5P supported the proposal of a new species—V. dinghuensis sp. nov. The description of this new species contributes to a more comprehensive understanding of the species diversity and biogeographical distribution of the genus Virescentia in China.