A new species of freshwater red algae, Sheathia jinchengensis, is described based on material collected from rocks in a clean and cold-water stream from the Jincheng region of Shanxi province in North China. Molecular sequences of rbcL and psbA genes were used to evaluate the phylogenetic relationship among samples of S. jinchengensis and other Sheathia species from several regions of the world. The results showed that S. jinchengensis formed an independent branch and separated from the previously published sequence data of other Sheathia taxa. From a morphological point of view, this new species differs also from other species of the genus by the smaller diameter of whorls (167.0–312.5 μm) and larger carpogonium diameter (17.0–29.0 μm). Comparison of sequence variation and thallus morphology with other Sheathia taxa resulted in the proposal of the new species—S. jinchengensis. Additionally, two endemic Batrachospermum species described earlier from China i.e., B. hongdongense and B. longipedicellata are now transferred to the genus Sheathia based on the present study as S. hongdongensis (S.L.Xie & J.Feng) Han, Nan, Feng, Lv, Liu, Kociolek et Xie comb. nov. and S. longipedicellata (Hua & Shi) Han, Nan, Feng, Lv, Liu, Kociolek et Xie comb. nov.

The morphological characterization and phylogenetic analysis based on molecular methods were executed on the freshwater Hildenbrandia specimens collected in this study. The cell size and filament height of the specimen collected from Pipa Lake, Japan were larger than the widely recognized species Hildenbrandia angolensis and Hildenbrandia rivularis, whereas overlapped with Hildenbrandia jigongshanensis. Based on molecular evidences of rbcL phylogenetic analysis and comparison of ITS1 secondary structure, specimen collected from Shiga Prefecture, Japan was proposed as a new species Hildenbrandia japananense. It brings the freshwater Hildenbrandia species in Japan to two. The specimens collected from Niangziguan, Shanxi province, China represent two new records of H. jigongshanensis. It enriches the species diversity of genus Hildenbrandia and increases the distribution diversity of this freshwater red algal taxon.

Four putative “Chantransia” isolates were collected from four locations in Hubei and Yunnan Provinces, China. Morphological analyses were conducted on all isolates. Two specimens (HB26 and YN2) fit the morphological description of A. pygmaea, while the other two isolates (YN1 and YN3) varied in morphology, but were within the circumscription of Audouinella hermannii. Due to the fact that the morphological characters of the “Chantransia” stages of order Batrachospermales and the species of genus Audouinella are too similar to be distinguished, a molecular analysis was performed to clarify the phylogenetic position of these four isolates based on rbcL and psbA sequences. Two “pygmaea” specimens collected from Jiugong Mountain, Hubei Province (HB26) and Shimen Gorge, Yunnan Province (YN2), such as S. jiugongshanensis and S. shimenxiaensis, are proposed primarily based on the DNA sequence data generated in this study. The description of these two new species provides more molecular data for phylogenetic analysis of the genus Sheathia. In addition to these newly described species, the results strongly support that those “hermannii” isolates (YN1 and YN3) collected from Yunnan Province were the “Chantransia” of S. arcuata. However, their gametophyte stages have not been found, meaning that critical diagnostic morphological features were unavailable and molecular methods were the only means for ascertaining their phylogenetic position. Considering the extensive application of the rbcL and psbA genes in phylogenetic analyses of freshwater red algae, we recommend using these two genes to identify species when no morphological characteristics are available.

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A new species of freshwater red alga, Sheathia matouensis, is described and illustrated based on material collected in spring water from the Hongdong region of Shanxi province, China. Phylogenetic analysis of sequence data from the rbcL and psbA indicated the separation between S. matouensis and the other species of genus Sheathia. Additionally, from a morphological point of view, S. matouensis differs from other species of the genus Sheathia by the smaller whorls and carpogonium. Therefore, the results based on both morphological observation and molecular evidences facilitated the proposal of this new species - S. matouensis. It represents another species in the freshwater red algal diversity in China and the description of this new species provides more molecular data for phylogenetic analysis of genus Sheathia.