Piper kiminensis Gajurel, T. Yakang & S. Kashung, 2025

Gajurel, Padma Raj, Yakang, Tage, Kashung, Soyala & Borah, Dipankar, 2025, Piper kiminensis (Piperaceae) a new species with shingling variegated leaves from Arunachal Pradesh, India, Phytotaxa 689 (2), pp. 269-276 : 270-273

Piper kiminensis Gajurel, T. Yakang & S. Kashung , sp. nov. ( Fig. 2 )

The new species is different from other climbing species of Piper due to its vegetative branches (orthotropic shoots) with a shingling (=overlapping) leaf pattern and relatively short internodes. This is similar only to P. obtusissimum Miquel (1844: 337) , a rare species of the Indo-Malayan region, but from which Piper kiminensis can be distinguished based on the variegated white patches on the adaxial leaf surface, in contrast with the solid green pigmentation of P. obtusissimum . Although the fertile branch and male spike orientation somewhat resemble that of P. betleoides Candolle (1923: 186) , a species occurring in the Eastern Himalayan region, P. kiminensis can be recognized based on vegetative morphology alone, including much shorter internodes (3–5 vs. 18–20 cm), smaller leaves (6–9 × 5–8 cm vs. 12–13.5 × 9–11 cm), and coriaceous, variegated leaves with dense pubescence on both surfaces (vs. membranous, solid green, and glabrous).

Type: — INDIA. Arunachal Pradesh: Papum Pare district, Kimin forest, 800 m, 27°34’61”E, 93°85’27”N, 25 October 2022, P. R. Gajurel 2705 (male) (holotype CAL!, isotype ARUN!).

Low creeping and climbing vine, with dimorphic branches. Vegetative branch: Stems terete, herbaceous, densely hirsute (soft white hairs), adventitious roots present at nodes and hairy; internodes 3–5 cm long. Leaves alternate, shingling (overlapping), broadly ovate, entire and ciliate, 6–9 × 5–8 cm, base deeply cordate, apex acute, 3 pairs of primary veins arising from the base, adaxially dark green with variegated white patches, velvety to the touch, but sparsely hairy, abaxially light green, with prominent, impressed secondary veins, hairy along the veins; petioles 1–1.5 cm long, finely pubescent. Stipules 0.2 cm long, densely hairy. Fertile branch: Stems terete without adventitious roots at nodes, finely pubescent, velvety to the touch; internodes 7–17 cm long. Leaves alternate, non-overlapping, ovatelanceolate, entire, 10–15 × 4.5–6.5 cm, base asymmetric with basal lobe overlapping petiole, apex narrowly acuminate, overall with 7–9 primary veins, the longer side of blade with 5–7 veins arising from the base and with the 2 anterior veins arising from 1–2.5 cm above the base, adaxially dark green, hispid on surface and along margin, scabrous to the touch, abaxially light green, finely hispid with more pubescence along the veins; petioles sub-sessile, 0.3–0.4 cm long, finely pubescent. Stipules 0.2 cm long, scaly, hairy. Prophylls present, finely pubescent. Spikes (male) leaf-opposed, 2.5–3.5 × 0.5 cm, pendulous; peduncles 2–2.8 cm long, finely pubescent, recurved at the point of attachment to the node; stamens 2, 1 mm long, compacted together on the rachis, subtended by a hairy orbicular bract, anthers bilobed, filaments short and hairy. Female plant not seen; fruits unknown.

Flowering: —October–November

Habitat and ecology: —Occurring at ca. 800 m elevation in a tropical forest with average annual rainfall of 3200 mm. It was observed that Piper kiminensis grows in moist, damp areas, close to streams, appressed along bare rocks and tree trunks in partial sunlight.

Distribution: —Known only from one area within the Kimin forest of Arunachal Pradesh, northeastern India ( Fig. 1 ).

Etymology: —The species epithet is based on the type locality of Kimin in the Papum Pare district of Arunachal Pradesh.

Conservation status: — Arunachal Pradesh is a developing state, currently in the process of mountain cutting and forest clearing for road building, causing significant threats to natural ecosystems. Given that this species has a very limited population size and occurs in a highly disturbed area, it is under high risk of extinction due to habitat destruction. Only 12 individuals could be located within 10 km 2, of which only two were mature male plants. Based on the present distribution and status of occurrence, it can be classified as Critically Endangered (CR) applying IUCN criteria B1a/b, B2a/b, and D (IUCN 2001). Ex situ conservation of the species has been initiated through vegetative propagation in the Department of Biotechnology— Arunachal Pradesh State Council for Science and Technology (DBT-APSCS&T) centre located in Kimin, as well as the nursery of the Forestry Department of the North Eastern Regional Institute of Science and Technology (NERIST).

Taxonomic notes: —As noted above, this species has vegetative branches similar to Piper obtusissimum and fertile branches similar to Piper betleoides ( Fig. 3 ). However, as summarized in Table 1, there are numerous differences that can be used to help distinguish between these three species.

obtusissimum are based on Suwanphakdee et al. (2023).

Gajurel and Lua (2020), in their work concerning Singaporean pipers, indicated that the fertile shoots of P. obtusissimum had never been recorded and described. However, in a recent paper about some pipers from Thailand ( Suwanphakdee et al. 2023), the reproductive branches with male and female inflorescence of this species were described and illustrated.

Figures

FIGURE 1. Outline map of India with the state Arunachal Pradesh showing the specific location of the new species.

FIGURE 2. Piper kiminensis (a) Habit (b) Adaxial view of vegetative and reproductive branches (c) Abaxial view of vegetative and reproductive branches (d) Vegetative (top) and reproductive (bottom) stem (e) Stipule at the base of petiole (f–g) A male spike with peduncle (h) Microscopic view of male flowers (i) Stamen along with bract. Photographs by T. Yakang.

FIGURE 3. Comparison of vegetative branch of (a) P. kiminensis with (b) P. obtusissimum and reproductive branch of (c) P. kiminensis with (d) P. betleoides. Photographs by T. Yakang and Lua H.K.