We conducted molecular phylogenetic analyses of plants treated as Sedum alfredii or S. formosanum collected from Japan, Taiwan, and the Philippines (Batan Island) with other 19 Sedum species primarily in East Asia using the internal transcribed spacer region of nuclear DNA to reexamine the taxonomic status of S. formosanum. Our results indicate that 15 plants treated as S. alfredii or S. formosanum included a clade with two Taiwanese endemic species, but were not sister to S. alfredii from Guangdong, China. In conclusion, this study supports the taxonomic treatment of Hatusima (1975), Ohba (1984, 2001), and Tang and Huang (1993) of S. formosanum as a separate species from S. alfredii.
Ito et al. (2014) studied this question.