Characterisation of Dysosma tonkinense (Gagnep.) M. Hiroe (Berberidaceae) based on morphological characteristics and ITS sequences

Dysosma tonkinense (Gagnep.) M. Hiroe is a traditional medicinal plant in Vietnam, called 'Bat giac lien' in Vietnamese. Based on similarities in morphological characters, it has been treated as a synonym of either P. versipelle Hance subsp. versipelle or D. difformis. In order to define a taxonomic treatment and find out the relationship between 'Bat giac lien' and those two similar species, a combination of morphological and ITS sequence analysis was applied. The morphological comparison showed that Dysosma tonkinense is distinguished from the two similar species in several characters, including rhizomes, leaf shape, size of floral organs, fruit shape and color, and seeds. Molecular data from ITS nrDNA sequences showed that D. tonkinense can be distinguished from other Dysosma spp. by three autapomorphic characters and a phylogenetic reconstruction recovered it as sister to D. difformis. Thus, we conclude that D. tonkinense should be recognized as a distinct species. These data also confirm that D. tonkinense is more closely related to D. difformis than to D. versipellis. In addition, new distributional records for D. tonkinense in the central districts of Vietnam, which is likely the southernmost occurrence of the genus, are presented.