Morphology and phylogenetic position of a freshwater Prasiola species (Prasiolales, Chlorophyta) in Korea

The genus of leafy green algae, Prasiola Meneghini, includes marine, terrestrial, and freshwater species. A total of 11 species and one variety have been identified in China, Korea, and Japan. In Korea, Prasiola formosana var. coreana has been reported in Muncheon, North Korea, while a different type of Prasiola species has been reported in South Korea. The South Korean species has been found growing along a small stream originating from Chodanggul Cave, a limestone cave in Samcheok, Gangwon Province. Here, we revised the morphological characteristics of the South Korean Prasiola species and analyzed plastid rbcL, psaB, and tufA genes to clarify its identity. Although the external and anatomical morphologies varied among individuals, our results were very similar to previous reports. Plastid three genes sequences of the South Korean specimens were identical to those of P. japonica collected from Japan as well as to published sequences of P. yunnanica from China. A short rbcL-3P sequence (196 bp) from P. formosana var. coreana, which was identified in the type specimen, was also identical to a sequence from P. japonica. These Prasiola species and variety from Korea, Japan, and China are all distributed in areas characterized by limestone bedrock. Based on morphological, phylogenetic, and distributional features, the South Korean Prasiola species is regarded herein as P. japonica. Here, we also propose to synonymize P. formosana var. coreana and P. yunnanica with P. japonica.