Hyoscyamus labiatus sp. nov. (Solanaceae: Hyoscyameae) from Henan, China: implications for the delimitation of Hyoscyamus

Background: Hyoscyamus , the largest genus in the tribe Hyoscyameae, harbors more than 20 species. Although the monophyly of Hyoscyamus is supported by both morphological and molecular phylogenetic studies, the delimitation of Hyoscyamus has been hotly debated in different classifications. Here, we report a new species of Hyoscyamus (Solanaceae) from Henan Province, China, and discuss the delimitation of Hyoscyamus . Results This species is morphologically similar to the known species of Hyoscyamus and its close related genus Archihyoscyamus , but can be distinguished by corolla 2-lipped, adaxial lip 3-lobed and much longer than abaxial lips, tube slender at base, and stamens 5, inserted on inner side of disk, free, obviously unequal, and exceeding corolla. Phylogenetic analysis based on four chloroplast markers including rbcL , ndhF , trnC - psbM and trnL-trnF , strongly suggested that the new species was sister to a monophyletic group containing all species of Hyoscyamus and Archihyoscyamus previously described. Conclusions Both the morphological observations and molecular phylogenetic analyses support the recognition of Hyoscyamus labiatus as a new species. Our study also showed that Archihyoscyamus should be a synonym of Hyoscyamus . The delimitation of Hyoscyamus is thus revised in our study.