Further Botanical Exploration of Limestone Karst Habitats in Northeastern Thailand Reveals a New Yellow-Flowered Species of Boesenbergia Kuntze (Zingiberaceae)

Limestone karst habitats in tropical Asia support specialized and geographically restricted plant diversity, yet many areas remain incompletely explored. During botanical surveys of limestone habitats in northeastern Thailand, a distinctive, yellow-flowered population of Boesenbergia was discovered in Phu Pha Man District, Khon Kaen Province. Morphological observations were conducted on living plants in the natural population and spirit-preserved material, supplemented by comparisons with protologues, published descriptions, and herbarium material. Patterns of phenetic similarity among ten selected Boesenbergia taxa were evaluated using 32 morphological characters, Gower distance, UPGMA clustering, and principal coordinates analysis (PCoA). The population is described here as Boesenbergia calcicola Boonma, Saensouk & P.Saensouk, sp. nov. It is morphologically most comparable to B. petiolata but differs by its conspicuously exserted inflorescence, shorter bracts and flowers, distally puberulent floral tube, smaller puberulent lateral staminodes, and distinctive labellum color pattern. Phenetic analyses were used to summarize patterns of overall morphological similarity among the examined taxa. The species is currently known only from its limestone type locality at approximately 385 m a.s.l. and is provisionally assessed as Data Deficient (DD). This discovery further documents localized Boesenbergia diversity associated with limestone karst habitats in northeastern Thailand.