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

Argostemma sawmlianae (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 A. courtallense and A. sarmentosum, 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 matK (cpDNA) and ITS 2 (nrDNA) sequences support the morphological evidences confirming A. sawmlianae 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.