Peperomia irrasa G. Mathieu, 2020

Mathieu, Guido, 2020, Endemic Peperomia (Piperaceae) novelties from eastern Madagascar, Candollea 75 (1), pp. 75-82 : 76

Peperomia irrasa G. Mathieu , sp. nov. ( Fig. 1 ).

Holotypus: MADAGASCAR. Reg. SAVA [Prov. Antsiranana]: massif de l’Anjanaharibe (pentes et sommet N), W d’Andapa, [14°43'S 49°30'E], 1700 m, 10.XII.1950 – 3.I.1951, Humbert, Capuron & Cours 24638 ( P [ P00106743 ]!; iso-: BR [ BR000000651342 ]!) .

Peperomia irrasa G. Mathieu differs from P. nicolliae G. Mathieu and P. silvicola C. DC. by the pubescent stem and petiole and by the emarginate leaf apex.

Perennial terrestrial herb, 10–15(–20) cm tall, spreading by stolons. Stem slender, simple or 1–2 branched, erect or basally decumbent and there rooting at the nodes, internodes 1–3 cm long, pubescence moderately dense, trichomes very short, two internodal ribs faintly visible, reddish. Leaves 2–4(–5)-verticillate; petiole 2–4 mm long, sulcate, sulcus pubescent, reddish; lamina succulent, obovate, (0.5–)1– 1.7 × (0.3 –)0.5(–1) cm, length/width ratio (1.1–)1.4(–1.9), apex rounded, distinctly emarginate, base acute to cuneate, 3-palmatinerved, only main nerve distinct, adaxially nerves slightly impressed, abaxially main nerve slightly protruding basally, adaxially discretely pubescent at the main nerve (most dense in the basal part) and in a periapical zone, abaxially glabrous, sometimes except for a small part along the base of the main nerve, margin apically ciliate, bright green adaxially, whitish green abaxially. Inflorescence 1 – 3 terminal spadices, peduncle ca 1 cm long, rachis 3–4 cm long in anthesis. Mature fruit not seen.

Etymology. – The specific epithet irrasa (“unshaven”) refers to the minute pubescent indument of stem and petioles, resembling a stubble beard ( Fig. 1B ), a key character of the species.

Distribution and habitat. – The new species is known from only three collections (Cours 3861 being probably a duplicate of one of Humbert’s), made during the same expedition in December 1951 - January 1952 in the Anjanaharibe massif in the region of SAVA and has apparently not been reported since. It occurs at an altitude of 1600–1800 m, in the upper part of the medium altitude moist evergreen forest (sensu GAUTIER et al., 2018) corresponding to the “Sylve à Lichen” of HUMBERT (1955). It is believed to be endemic from the Anjanaharibe massif. The collections show only young inflorescences without mature fruits.

Conservation status. – Peperomia irrasa is known from three (most likely two) old specimens collected most likely in a single location from Anjanaharibe Sud National Park. Despite the very restricted distribution and the absence of recent collection, there appear to be no current threats, and thus P. irrasa is assigned a status of “Least Concern” [LC] using the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Peperomia irrasa can easily be distinguished from other Malagasy species with small opposite or verticillate leaves by the distinct emarginate leaf apex. The short erect trichomes of the stem provide confirmation. Peperomia nicolliae G. Mathieu exhibits longer trichomes, curved in apical direction, whereas P. silvicola C. DC. exhibits a villous indument. One other Malagasy Peperomia shows leaves with a distinct emarginate leaf apex: P. thomeana C. DC. , but that species shows alternate leaves. Peperomia irrasa is considered as belonging to Peperomia subg. Micropiper (Miq.) Miq. , as it is the case with P. nicolliae and P. silvicola ( FRENZKE et al., 2015) .

Paratypi. – MADAGASCAR. Reg. SAVA [Prov. Antsiranana]: Anjanaharibe , [14°43'S 49°30'E], 1700 m, 25.XII.1950, Cours et al. 3861 ( P, TAN) ; ibid. loco, 1600–1800 m, 10.XII.1950 – 3.I.1951, Humbert et al. 24635 ( BR, P).

Figures

Fig. 1. – Peperomia irrasa G. Mathieu. A. General habit; B. Detail of node; C. Detail of leaf apex. [Humbert 24638, BR, P] [Drawing: G. Mathieu]