A revision of the imbricate group of Styrax series Cyrta (Styracaceae) in Asia

Several taxonomic treatments of Styrax (Styracaceae) exist in regional floras of Asia, but the Asian species of the genus have not been comprehensively revised since 1907. To help rectify this, we conducted a taxonomic revision of the Asian species of Styrax series Cyrta with imbricate corolla aestivation. Our revision comprises 17 species with a combined distribution from Japan south to Sumatra and west to Nepal. The circumscriptions of the heretofore poorly defined species S. hookeri and S. serrulatus are clarified. Styrax agrestis var. curvirostratus is elevated to the species level, and lectotypes are selected for S. duclouxii, S. floribundus, S. hemsleyanus, S. hookeri, S. hookeri var. yunnanensis, S. hypoglaucus, S. japonicus, S. limprichtii, S. macranthus, S. obassia, S. perkinsiae, S. serrulatus var. latifolius, S. shiraianus, S. supaii, and S. wilsonii. Keys, descriptions, and distribution maps are provided for all species.