Abstract: Recent molecular phylogenetic analyses on Primula have greatly enhanced the understanding of the infrageneric relationships of the genus, but the subgenera Auganthus and Carolinella remain meagerly sampled and poorly understood. In this study, nucleotide sequence data of three chloroplast DNA regions (matK, rps16, and trnL-F) were employed to infer phylogenetic relationships of the subgenera Auganthus and Carolinella. Sequence data were acquired and analyzed for 70 species of Primula and its close relatives. The data matrix included 29 species (42%) of subgenus Auganthus and 5 species (50%) from subgenus Carolinella. Phylogenetic analyses on these data showed that the sampled species of the subgenus Carolinella do not form a monophyletic clade, but dispersed among the species of the subgenus Auganthus. Neither subgenus Auganthus nor Carolinella is therefore monophyletic under their current circumscriptions. The distinctive calyptrate capsule that was previously used as a diagnostic criterion for subgenus Carolinella was inferred to have evolved multiple times in Primula based on the phylogeny. Our analysis also confirmed that Cortusa is nested within subgenus Auganthus. We, therefore, suggest a revised circumscription of subgenus Auganthus to include subgenus Carolinella and the genus Cortusa. Several clades were identified with this broadly defined subgenus Auganthus by the phylogenetic analyses, but their relationships remain incompletely resolved.

Key words: Auganthus, calyptrate capsule, Carolinella, Circumscription, Primula, Primulaceae.