Rhododendron jiucaipingensis (Ericaceae), a new species from Guizhou, China

Rhododendron jiucaipingensis Jian Xu & M. T. An, sp. nov. (Ericaceae), a new species of R. subgen. Hymenanthes, subsect.

Argyrophylla, from northwestern Guizhou, China, is described and illustrated. It is an evergreen shrub 1.5–3.0 m tall, characterized by green, densely white-tomentose current-year branchlets, leaves crowded at branch apices (5.5–9.5 × 2.5–4.0 cm) with 8–11 pairs of lateral veins, 10 stamens, and cylindric capsules 1.2–2.0 cm long. The new species is morphologically most similar to R. hypoglaucum and R. argyrophyllum, but it is readily distinguished by having densely white-tomentose current-year branchlets, fewer lateral veins (8–11 pairs), a double-layered white indumentum on the abaxial surfaces of young leaves, and 10 stamens.

Phylogenetic analysis based on a whole-genome SNP dataset robustly resolves R. jiucaipingensis as a distinct lineage within subsect. Argyrophylla, positioned as sister to the monophyletic clade of five congeneric species with high support (SH-aLRT = 100 %, UFBoot = 100 %). This molecular evidence, congruent with diagnostic morphological characters, supports the recognition of R. jiucaipingensis as a species new to science.