Peperomia mangalbaria P.Rai & G.Mathieu, 2023

Rai, Pramod & Mathieu, Guido, 2023, Peperomia mangalbaria (Piperaceae), a new species from Sikkim Himalaya, India, Phytotaxa 609 (2), pp. 138-144 : 139-141

Peperomia mangalbaria P.Rai & G.Mathieu sp. nov. ( Figs. 1 & 2 )

Type:— INDIA. Sikkim: Soreng district, Mangalbaria , collected from epipetric habitat, 27°11’40.08”N, 88°18’31.00”E, 970 m, 9 June 2020, P. Rai PO503 (holotype BSHC!, isotype DARJL!) .

Diagnosis:— Peperomia mangalbaria resembles the widespread Old World species Peperomia leptostachya in habitat preference, plant size, general leaf morphology, and axillary or terminal inflorescence position. However, it is distinct by its trailing habit (vs. erect), leaf apex obtuse or rounded (vs. acute), leaf indument pubescent abaxially and glabrescent adaxially (vs. both sides puberulous) and pinnatinerved leaves (vs. palmatinerved).

Perennial herbs, epiphytic or epipetric. Stems trailing, 10–50 cm long, 2–3 mm diameter, with ascending branches; young branches light green, pubescent, matured ones dark green and mottled with reddish-brown spots and longitudinal stripes; rooting from the nodes; internodes 1–5 cm long, basal internodes longest, terete. Leaves opposite or 3–4- verticillate; petioles 0.3–1 cm long, pubescent; laminae 0.8–3 × 0.5–2.5 cm, ovate, ovate-elliptic, obovate, orbicular, suborbicular, or obcordate, sometimes asymmetric, basal leaves smaller and thicker, terminal ones larger and thinner, both sides pubescent when young, adaxially glabrescent at maturity, abaxially more densely pubescent than adaxially, deep green adaxially, silvery-green abaxially; obscurely 3- to 5-pinnatinerved, the central nerve with side branches in larger leaves, margin entire, ciliate, base cuneate or rounded, apex rounded, obtuse, or emarginate. Inflorescences 2–4 (–5) terminal spikes, sometimes solitary on shorter branches, erect or sub-erect; peduncles 0.3–0.5 cm long, glabrous or sparsely pubescent; rachis glabrous, 1.5–5 cm long, ca. 2 mm in diameter; rachial pits dark green, oval; floral bracts peltate, green, erect at the fertile pits, otherwise adpressed, inserted at base of rachial pit, ca. 1 mm in diameter; stamens two, anthers white, ovoid, exerted at maturity, ca. 2 × 1 mm; ovary ovoid, stigma cup-shaped, ca. 3 × 1 mm, translucent, white. Fruits slightly pseudo-pedicellate, spaced 1–2 mm apart, ovoid to globose, ca. 2 mm in diameter, yellowish-green to dark brown at maturity; pericarp entirely covered with white, sticky papillae; style conical, without papillae.

Additional specimens examined (paratypes):— INDIA. Gangtok district : Lumsey, above Ranikholaa, 27°19’13.00”N, 88°35’36.67”E, 910 m, 23 September 2021, P . Rai P0832 ( BSHC); Adampool , vicinity of Singabahini Temple, 27°18’40.90”N, 88°34’53.44”E, 900 m, 23 September 2021, P . Rai P0834 ( DARJL); Rumtek , between Ranikholaa and Raniban Homestay, 27°18’10.55”N, 88°34’56.66”E, 885 m, 14 October 2022, P . Rai P0836 ( BSHC). Namchi district : Assangthang, below 9 th Mail, 27°09’47.08”N, 88°19’29.00”E, 900 m, 13 June 2021, P . Rai P0504 ( DARJL). Soreng district : Tato pani, 27°14’46.07”N, 88°18’09.00”E, 500 m, 4 August 2020, P . Rai P0840 ( DARJL) .

Phenology:—This species has been found flowering from June to September and fruiting from July to October.

Distribution:—Currently considered as endemic to India, state of Sikkim (Adampool, Lumsey, Mangalbaria, Rumtek, and Tato Pani), 500–970 m ( Fig. 3 ).

Etymology:—The specific epithet denotes Mangalbaria (also Mangalbarey), a town in Soreng, a district of Sikkim, India and the type locality of the new species. The epithet is used as a noun in apposition.

Note:—Based on vegetative, flowering as well as fruiting characters, P.mangalbaria can be classified in Peperomia subsp. Micropiper (Miq.) Miq. ( Miquel 1843:45,76) ( Frenzke et al. 2015: 427). The taxonomically similar taxon P. leptostachya belongs to the same subgenus and both species are compared in Table 1 .

Ecology:—Plants prefer cooler shaded habitats in tropical or subtropical biomes. It is apparently drought tolerant due to the thickened stem that can withstand prolonged dry periods. It may grow as epiphyte as well as epipetric. Epiphytic populations were seen on basal trunks of tree species such as Bauhinia Linnaeus (1753: 374) , Dalbergia Linnaeus f. (1782: 316) and Albizia Durazzini (1772: 11) . Epipetric populations were growing together with mosses and ferns such as Adiantum Linnaeus (1753:1094) and Pyrrosia Mirbel in Lamarck & Mirbel (1803: 471).

Conservation status:—Currently, the new species is known from only three districts of Sikkim, viz. Gangtok, Namchi, and Soreng, with three, one and two populations, respectively. The Namchi population is ca. 29 km southwest from the Gangtok populations, and the Soreng populations are ca. 34 km northwest of Namchi (see Fig. 3 ). On further assessment of the populations using GeoCAT Geospatial Conservation Assessment tool, Area of Occupancy and Extent of Occurrence were 24 km ² and 185.841 km ², respectively. Therefore, it is proposed to consider this species as Endangered (EN) (IUCN 2022).

Figures

FIGURE 1. Color plate of Peperomia mangalbaria P. Rai & G. Mathieu. A. Habitat (epipetric). B. Inflorescence with glabrous rachis. C. Infructescence with globose, papillate fruits. D. Spikes. E. Leaf surfaces (left abaxial, right adaxial) F. Detail of stem showing mottled appearance (green with red striping). G. Ciliate leaf margin. H. Young shoot. I. Habitat (epiphytic).

FIGURE 2. Line drawing of Peperomia mangalbaria P.Rai & G. Mathieu.A. Inflorescence with glabrous rachis.B. Ciliate leaf margin.C. Infructescence with globose, papillate fruits. D. Leaf of P. leptostachya showing conspicuous palmate venation. E. Leaf of P. mangalbaria showing obscure pinnate or plinerved venation. F. Habitat of plant with detail of stem to show striping and pubescence.

FIGURE 3. Distribution map of P. mangalbaria in southern portion of Sikkim, India, within the districts of Gangtok, Namchi, and Soreng. Red dots indicate individual populations/collection sites.