Curcuma borealis sp. nov. and C. retrocalcaria sp. nov. (Zingiberaceae): Two Novel Taxa from Northern Thailand

This study introduces Curcuma borealis Saensouk, P.Saensouk, and Boonma and C. retrocalcaria Saensouk, P.Saensouk, and Boonma, two newly discovered species within the Curcuma genus of the Zingiberaceae family, found in the Mae Hong Son and Chiang Mai Provinces of Northern Thailand, respectively. This research aims to clarify the taxonomic identity of these species, which were initially confused with C. ecomata Craib and C. chantaranothaii Boonma and Saensouk due to similarities in flower coloration and some morphological characteristics, respectively. Detailed morphological analysis was conducted to distinguish these species. Curcuma borealis is differentiated by its unique anthers lacking appendages or projections at the base of the spurs, in contrast to the appendages or projections present in C. ecomata, while C. retrocalcaria is characterized by anther spurs folding or curving backward under the anther base and with two purple patches at the base of the labellum, distinguishing it from C. chantaranothaii. The findings highlight distinct morphological traits that set C. borealis and C. retrocalcaria apart from existing Curcuma species. The pollen morphology of the two new taxa was also studied here for the first time. This research emphasizes the importance of thorough taxonomic scrutiny for accurate species identification and contributes to our understanding of the diversity within the Curcuma genus. Accurate identification of these species is crucial for conservation efforts, underscoring the need to protect their habitats and maintain biodiversity in the region.