Distribution and conservation status of Camellia longzhouensis (Theaceae), a critically endangered plant species endemic to southern China

•There were only 58 individuals of Camellia longzhouensis in three sub-populations.•The population structure of C. longzhouensis is spindle-shaped.•Its abundance was related with soil fertility and light intensity.•It was reassessed as Critically Endangered C2a(i,ii).•Integrated conservation approach of rare plants is needed in karst poor areas.