A new revision of the lichen genus Pleopsidium (Acarosporales, Acarosporaceae) in China reveals two new species

Based on a combination of morphological, chemical, and phylogenetic analyses, we present a new revision of the lichen genus <i>Pleopsidium</i> in China. <i>Pleopsidiumtumidulum</i> <b>sp. nov.</b> and <i>P.corrugatulum</i> <b>sp. nov.</b> are proposed as new species to science, both included in a distinctive clade (clade 1) together with <i>P.gobiense</i>. These three species are characterized by the absence of fatty acids, acaranoic and acarenoic acids, and share similar ecological traits. In contrast, species containing fatty acids, including <i>Pleopsidiumflavum</i>, <i>P.chlorophanum</i>, and <i>P.discurrens</i>, constitute a separate clade (clade 2). Fresh specimens of <i>Pleopsidiumdiscurrens</i> were collected from the type locality, Yulong Snow Mountain, and molecular data were generated to confirm the phylogenetic position of the species. Our study additionally reveals substantial morphological variation in this species. New collections and sequences of <i>Pleopsidiumgobiense</i> from Hami City, the type locality, are provided, from which a neotype is designated, confirming its phylogenetic position. Differences in morphology, anatomy, chemistry, and ecology among <i>Pleopsidium</i> species from China are discussed. A key and several phylograms are provided.