Petrocodon gracilis (Gesneriaceae) is a synonym of P. mirus based on morphological and molecular data

Petrocodon gracilis T.Ding & B.Pan and P. mirus X.Z.Shi, J.X.Fu & Li H.Yang are two recently described species exhibiting nearly identical morphology. To determine whether they represent the same taxon, we compared their type localities, type materials, and morphological features and conducted phylogenetic analyses using the nuclear internal transcribed spacer (ITS) and five plastid regions (atpI-H, matK, rps16, trnH–psbA and trnL–F). Morphological comparisons and type information revealed that both species originated from the same population and are indistinguishable in key traits. Molecular phylogenetic analysis further showed that four samples of P. gracilis and P. mirus form a strongly supported monophyletic clade. Combined morphological and molecular evidence confirmed their conspecificity. We therefore treat P. gracilis as a synonym of P. mirus.