<i>Pogostemon puerensis</i> (Lamiaceae), a new species from Yunnan of China

<i>Pogostemon</i> is the largest genus in tribe Pogostemoneae (Lamiaceae) and exhibits considerable morphological diversity, which has complicated species delimitation in parts of Southeast Asia. During botanical surveys in Pu'er City, Yunnan Province, China, a distinctive population of <i>Pogostemon</i> resembling <i>P. hainanensis</i> and <i>P. parviflorus</i> was discovered but differs in several stable morphological characters. Its taxonomic status was assessed using comparative morphology and molecular phylogenetic analyses based on five plastid regions (<i>matK</i>, <i>psbA-trnH</i>, <i>rbcL</i>, <i>rps16</i>, <i>trnL-trnF</i>) and the nrITS region. The sampling included 57 accessions representing 35 species of <i>Pogostemon</i>, with representatives of other genera in Pogostemoneae and related tribes as outgroups. Bayesian and maximum likelihood analyses recovered the Pu'er plant as a well-supported lineage within <i>Pogostemon</i>, sister to <i>P. parviflorus</i> in the plastid dataset and to <i>P. cablin</i> in the nuclear dataset. Morphologically, it differs from <i>P. hainanensis</i>, <i>P. parviflorus</i>, and <i>P. cablin</i> by its much shorter bracteoles, distinctly exserted corolla, and longer stigma lobes; it is further distinguished from <i>P. hainanensis</i> and <i>P. parviflorus</i> by the densely hairy upper two-thirds of the inner calyx tube and from <i>P. cablin</i> by its different phenology. It is therefore described as a new species, <i>Pogostemon puerensis</i> X.X.Wu, Z.H.Li & Qiang Wang.