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| Argostemma sawmlianae Lalhlupuii, Tlanhlui, S.D.Khomdram & S.D.Yumkham, in Lalhlupuii, Tlanhlui, Khomdram et Yumkham. 2025. |
Abstract
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 ITS2 (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.
Key words: Argostemma, Indo-Burma hotspot, Mizoram, molecular, morphology, new species
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| Argostemma sawmlianae Lalhlupuii, Tlanhlui, S.D.Khomdram & S.D.Yumkham, sp. nov. A, B. Habit; C. Anisophyllous leaves with inflorescence (inverted view); D. Leaf with stipule; E, F. Anisophyllous leaves; G. Flower with bract; H. Inflorescence; I. Foliaceous bracts; J. Rudimentary leaves; K. Petaloid calyx with green tips; L. Corolla with green blotched tubes; M. Corolla with reflexed and backwardly rolled lobes; N. Single falcate shaped corolla lobe; O. Corolla lobes; P. Single stamen with curved filament; Q. Androecium with loosely arranged stamens. (photos by Margaret Lalhlupuii & Lal Tlanhlui). |
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| Argostemma sawmlianae Lalhlupuii, Tlanhlui, S.D.Khomdram & S.D.Yumkham, sp. nov. A. Single flower; B. Pistil; C. Cross section of ovary; D. Seeds (LM image); E. Seed (SEM image); F. Pollen (SEM image); G. A. sawmlianae in type locality; H, I. A. verticillatum from Manipur; J. A. kamjongense from Manipur; K. A. sarmentosum from Meghalaya. (photos by Margaret Lalhlupuii, Lal Tlanhlui & Yumkham). |
Argostemma sawmlianae Lalhlupuii, Tlanhlui, S.D.Khomdram & S.D.Yumkham, sp. nov.
Diagnosis. It is similar to Argostemma courtallense Arn. and A. sarmentosum Wall., but differs from the two in having one 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 petals which are reflexed and strongly rolled backwards (Fig. 3, Table 1).
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Margaret Lalhlupuii, Lal Tlanhlui, Sandhyarani Devi Khomdram, Sanatombi Devi Yumkham. 2025. Argostemma sawmlianae (Rubiaceae, Argostemmateae), A New Species from Northeast India under the Indo-Burma Hotspot. PhytoKeys. 266: 317-328. DOI: doi.org/10.3897/phytokeys.266.162537