Morphological supplement and taxonomic revision of Camellia rubimuricata: evidence from morphology, palynology and molecular systematics

Camellia sect. Tuberculata, characterized by tuberculate ovaries and a primary distribution in Guizhou Province, China, exhibits poorly resolved interspecific relationships due to limited field and experimental data. A prominent case is C. rubimuricata, which has historically been treated as a forma of C. ilicifolia—a taxonomic placement that has remained controversial. To clarify its status, we conducted extensive field surveys at the type locality of C. rubimuricata and carried out integrated morphological, palynological, and molecular phylogenetic analyses (using complete cpDNA and ITS sequences). Comparative morphology revealed clear distinctions between the two species in terms of floral structure, petals, sepals, and fruit. Pollen micromorphology further differentiated two species on the basis of the pollen shape, polar/equatorial ratio (P/E), germination pore structure, and exine ornamentation. Phylogenetic reconstructions from both the cpDNA and ITS datasets consistently placed C. rubimuricata and C. ilicifolia in distinct, strongly supported clades. Therefore, these multidisciplinary lines of evidence strongly support the recognition of C. rubimuricata as an independent species that is distinct from C. ilicifolia. Additionally, this study provides the first comprehensive documentation of several key morphological traits of C. rubimuricata.