Phylogenetic position, supplementary description and phytochemical analysis of (Theaceae), a critically endangered tree native to Hekou, Yunnan, China.

harbors unique diversity along Sino-Vietnamese border. Some species of them are under threat due to human activity. , a native of Hekou, Yunnan, China, was once considered extinct as the previously known "last living tree" died in 2024. Fortunately, 11 in-situ and 32 ex-situ trees have been protected and propagated by the staff of Hekou Administration Branch of Dawei Mountain National Nature Reserve in Yunnan with their great unpublicized efforts. Molecular phylogenetic analysis suggests that is nested in the main clade CI of and forms a clade with , and , which are generally distributed in Vietnam. Morphological characters of the capsule and seed of are supplementally described. The leaves of contain 1.18 mg/g theobromine, which disagrees with the previous chemotaxonomic claim. Though the economic and ecological values are little known for , the species should be conserved and propagated effectively and promptly to prevent extinction.