Taxonomic revision of some taxa in Kaempferia subgenus Protanthium (Zingiberaceae) revealing a new species from Thailand and two new synonyms

Kaempferia subglobosa (Zingiberaceae) is described and illustrated as a new species of Kaempferia subg. Protanthium from Tak Province, northern Thailand. It can easily be distinguished from all other species of subg. Protanthium by having branched storage roots with numerous, tiny, lateral and terminal subglobose to ovoid tubers. The diagnostic characters of this taxon are discussed and compared with those of the morphologically most similar species K. rotunda. Detailed photographs of plants and dissected flowers, and information on phenology, distribution and ecology, are provided. Interestingly, a red dwarf honeybee, Apis florea, is likely a pollinator. The IUCN conservation status of Vulnerable is assigned for K. subglobosa. In addition, the names K. uttaraditensis and K. kamthornii are synonymized with K. albiflora and K. takensis, respectively. As a result of this taxonomic revision, the Flora of Thailand currently harbours 14 species of the subgenus of which 9 strictly endemic. Two alternative updated identification keys for Kaempferia subg. Protanthium are also presented.