Authors: Li, Peng-Wei; Liu, Fang-Pu; Han, Meng-Qi; Smith, James F.; Wang, Yin-Zheng
Publication: Annals of the Missouri Botanical Garden
Year: 2022
Genera: Deinostigma, Metapetrocosmea

Metapetrocosmea W. T. Wang and Deinostigma W. T. Wang & Z. Y. Li were originally monotypic with M. peltata (Merr. & Chun) W. T. Wang and D. poilanei (Pellegr.) W. T. Wang & Z. Y. Li, respectively. Recent molecular phylogenetic research expanded Deinostigma to include several species previously transferred from Chirita D. Don to Primulina Hance. However, the relationship between Metapetrocosmea and Deinostigma has not been well addressed. In the present study, the type species of Metapetrocosmea and Deinostigma were sampled together with related taxa, and the systematic relationships were reexamined using the nuclear ribosomal internal and external transcribed spacer regions (ITS and ETS) and four chloroplast regions (rpL32-trnL, rps16, trnH-psbA, trnL-F). Phylogenetic analyses demonstrate that M. peltata is embedded in the species of Deinostigma and sister to D. poilanei. All of these species form a highly supported branch, i.e., Metapetrocosmea–Deinostigma clade, which is sister to Oreocharis Benth. Morphological analyses show that species in the Metapetrocosmea–Deinostigma clade share a series of morphological traits, i.e., alternate leaves, arcuate filaments, densely lanate anthers with the hair surface covered with granular or vermiform appendages, bilobed stigma that vary from dorsal to ventral and almost equal in size to a dorsal-ventral oblique lamella with the dorsal one sterile, hooked hairs and T-shaped glandular hairs occurring on the whole plant, and riblike seed surfaces. Both molecular and morphological evidence strongly suggest that the Metapetrocosmea–Deinostigma clade is monophyletic and should be combined into a single genus, i.e., Metapetrocosmea W. T. Wang. Therefore, we present a taxonomic treatment for this group.