Argostemma sawmlianae (Rubiaceae, Argostemmateae), a new species from Northeast India under the Indo-Burma Hotspot

<i>Argostemma sawmlianae</i> (Rubiaceae), a new species from Mizoram, Northeast India, within the Indo-Burma hotspot, is described and illustrated. The species is compared with its allied species <i>A. courtallense</i> and <i>A. sarmentosum</i>, from which it differs by a set of distinctive morphological characters that include a pair of larger sessile leaves (11.5-18.5 cm long), longer peduncle (4-6.5 cm long), more flowers per cyme (8-33) and campanulate corolla with falcate lobes, reflexed and prominently rolled backward. The molecular analyses based on <i>matK</i> (cpDNA) and ITS2 (nrDNA) sequences support the morphological evidences confirming <i>A. sawmlianae</i> as a distinct new species. The newly discovered species is provisionally categorized as Critically Endangered (CR) in accordance with the IUCN Red List Categories and Criteria (IUCN 2024) based on available data.