Abstract
The freshwater red algal order Thoreales has a triphasic life history, of which the "Chantransia" phase is a small filamentous sporophyte. The "Chantransia" stage is difficult to distinguish from species in the genus Audouinella by its morphological characteristics. In this study, five "Chantransia" isolates (GX41, GX81, GD224, GD225, GD228) were collected from Guangxi Zhuang Autonomous Region and Guangdong Province in China. Based on morphological data, all five isolates were similar to A.pygmaea, whereas sequence data from the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) gene and the 5' region of the mitochondrial cytochrome oxidase I gene (COI-5P) determined that these specimens represented the "Chantransia" stage of two species in the genus Thorea rather than Audouinella. Phylogenetic analyses of the concatenated genes supported the proposal of a new species, T.baiyunensis, and a new geographic record of T.okadae, a species previously described only in Japan. Therefore, combined with previous records, four species of this genus are now recognized in China, including T.hispida, T.violacea, T.baiyunensis and T.okadae.