Resurrection of the genus Homostylium Nees for the former Aster ser. Albescentes Y.Ling (Astereae, Asteraceae), with an updated generic synopsis

Recent molecular phylogenetic studies have demonstrated extensive paraphyly of Asterser.Albescentes Y.Ling. This woody-based shrubby group is both morphologically and molecularly distinct from the genus <i>Aster</i> L. The series is characterized by its shrubby habit with multiple branches, cauline leaves with revolute or flat margins, radiate capitula, keeled phyllaries, and multinerved achenes. We redefine a more natural circumscription of this series by reinstating <i>Homostylium</i> Nees with nomenclatural priority. A taxonomic synopsis of this series is presented herein. <i>Homostylium</i> is recognized and described as a distinct genus (Astereae, Asteraceae) to accommodate 7 shrubby species (6 endemic to China) formerly placed in Asterser.Albescentes. A total of 19 new combinations are proposed, e.g., <i>Homostyliumalbescens</i> (DC.) Z.X.Fu, <b>comb. nov.</b> (incl. 10 varieties), <i>Homostyliumargyropholium</i> (Hand.-Mazz.) Z.X.Fu, <b>comb. nov.</b> (incl. 2 varieties), <i>Homostyliumfulgidulum</i> (Grierson) Z.X.Fu, <b>comb. nov.</b>, <i>Homostyliumhypoleucum</i> (Hand.-Mazz.) Z.X.Fu, <b>comb. nov.</b>, <i>Homostyliumlavandulifolium</i> (Hand.-Mazz.) Z.X.Fu, <b>comb. nov.</b>, <i>Homostyliummotuoense</i> (Y.L.Chen) Z.X.Fu, <b>comb. nov.</b>, and <i>Homostyliumpolium</i> (C.K.Schneid.) Z.X.Fu, <b>comb. nov.</b> Formal typifications, synonyms, illustrations, distribution maps, and an identification key to the species of <i>Homostylium</i> are also provided herein.