Rinorea ranirisonii Nusb. & Wahlert, 2013

Wahlert, Gregory A., Nusbaumer, Louis & Gautier, Laurent, 2013, Rinorea ranirisonii Nusb. & Wahlert (Violaceae), a new species from the Daraina region of northern Madagascar, Candollea 68 (1), pp. 87-92 : 88-90

Rinorea ranirisonii Nusb. & Wahlert , spec. nova ( Fig. 1 , 2 ).

Typus: MADAGASCAR. Prov. Antsiranana: Sous-préfecture de Vohemar , commune rurale de Daraina , forêt de Binara , 225 m, 13°14’19’’S 49°37’30’’E, 225 m, 27.III.2004, Ranirison 496 (holo-: G!; iso-: P!, MO!, K!, TEF, research herbarium of Daraina).

Arbuscula foliis oppositis, ab omnibus congeneribus sectionis Verticillatae in Madagascaria indumento oculo nudo dense hispido, aureo-rubro in ramulis annotinis, petiolis, nervura primaria laminae, pedunculo, pedicellis, sepalisque, oculo armato indumento conspicuo in ovario.

Shrub branched, up to 1.5 m tall; young branches flattened in cross section, quite canaliculated under the nodes, hispid. Leaves opposite, anisophyllous (1:1.3); petiole 10-20 mm long, with hispid golden reddish hairs 0.8-1.2 mm long, adaxially slightly canaliculated at the apex; stipules early caducous, not seen; terminal bud scales green, brown when dry, conical, linear-lanceolate, 2-4 mm long, 1-1.5 mm broad, hispid, apex acute, mucronate; lamina ovate, 2.8-8.2 × 2.0-5.0 cm, length to width ratio of 1.3-1.8, membranaceous, green and slightly discolorous, whitish on the lower surface, upper and lower surfaces hispid; primary and secondary veins densely hispid on both surfaces; secondary vein pairs 3-7, brochidodromous, divergent, tertiary veins reticulate; base rounded to truncate to subcordate, slightly asymmetrical, oblique; margin crenate, subrevolute; apex obtuse to rounded, mucronate. Inflorescence a terminal cyme, less than 2.5 cm long, axis hispid, peduncle 12-18 mm long, peduncle subtended by two persistent bud scales; pedicels 1.0- 1.5 mm long, hispid; pedicel bractlets persistent, deltoid-ovate, 0.7-1.5 × 0.2-0.5 mm, hispid, apex acute, mucronate. Flowers 3.4-4.0 mm long. Sepals five, cream at the base and gradually green to the apex, entire, unequal, imbricate, narrowly triangular, 2.1-3.5 × 1.0 mm, keeled, hispid, apex acute, mucronate, mucro dark red when dry. Petals five, contorted to the left, cream to white, subequal, lanceolate, 3.5-4.0 × 0.6-1.2 mm, outer surface glabrous, inner surface glabrous or with few-several hairs above the middle, margin entire, apex subacute, erect. Stamens white to cream, five, 1.5-1.8 mm long; staminal tube 0.6-0.8 mm tall, outer and inner surfaces glabrous; anthers subsessile, filaments 0.1- 0.2 mm long, anther connectives 0.5 × 0.5 mm; anther ventral appendages absent; anther dorsal connective scales apical, ovate, scarious, white, 0.5 × 0.3 mm, surface glabrous, margin entire, apex rounded, truncate or bifid. Pistil 30 mm long; ovary ovoid, 1.0 × 0.8 mm, hispid; style 20 mm long, erect, fluted in cross-section, straight, glabrous. Fruit not seen.

Remarks. – Rinorea ranirisonii is a distinctive species, yet it is not clear to which other opposite-leaved species in Rinorea subsect. Verticillatae it is most close related. With R. auriculata it shares a pedunculate cymose inflorescence (vs a contracted, subsessile inflorescence in most species), but is otherwise completely different in vegetative characters. R. ranirisonii differs from other species by the shape of its ovate leaf blade and the apex of the blade obtuse to rounded. It is also distinguished by its ovary covered in golden-reddish hispid indumentum, often densely so, as well as the young branches, upper and lower leaf surfaces, inflorescence axis, pedicels, and sepals.

Distribution. – The new species is only known from the forests of the Loky-Manambato (Daraina) region, in northeastern Madagascar ( Fig. 3 ). During botanical and vegetation studies in the region, only four individuals were observed among ca. 54 000 vascular plant observations. The four individuals were found in Binara, Ampondrabe, and Bobankora forests in the Loky-Manambato region. However we suspect the species may occur in several other forests across the entire Loky-Manambato region.

Habitat and ecology. – Rinorea ranirisonii occurs primarily in evergreen rainforest on slopes, and uncommonly in semi-deciduous forest along streams. The species grows in forests with canopies reaching 12 to 15 m on metamorphic rock, up to 500 m elevation. The most frequently recorded species occurring with R. ranirisonii in vegetation surveys include: Diospyros aff. quercina (Baill.) G. E. Schatz & Lowry , and Nesogordonia sp. as well as Vepris nitida (Baker) I. Verdc. , Salacia madagascariensis (Lam.) DC. , Ivodea mahanarica Capuron , Securinega durissima J. F. Gmel. and Wielandia bemarensis (Leandri) Petra Hoffm. & McPherson.

Phenology. – The species flowers from February to March.

Etymology. – The new species described in this paper is named in honor of Patrick Ranirison, who collected the type specimen and suspected it to represent a new species. Patrick Ranirison and L. Nusbaumer both earned their doctorate under the supervision of L. Gautier, and both spent months in the field together doing botanical inventories and vegetation studies in the forests of Loky- Manambato. Ranirison is a highly capable botanical researcher, a passionate conservationist, and a congenial companion in the field. The sakarivo link between P. Ranirison and L. Nusbaumer through their long collaboration and friendship is reserved for the closest and most loyal relationship between two friends.

Conservation status. – With an area of occupancy (AOO) of 36 km 2 and an extent of occurrence (EOO) of 227 km 2, and only four collections known among three subpopulations in the protected area of Loky-Manambato, Rinorea ranirisonii is assigned a preliminary status of “Endangered” (VU D1) following the IUCN Red List Categories and Criteria ( IUCN, 2001; calculation following MOAT (2007) and CALLMANDER & al. (2007)).

Other specimens examined. – MADAGASCAR. Prov. Antsiranana: Sous-préfecture de Vohemar , commune rurale de Daraina , forêt d’Ampondrabe , 12°57’13’’S 49°42’31’’E, 460 m, 21.II. 2005, fl. bud, Nusbaumer & Ranirison 2265 ( G); same locality description, 12°57’04’’S 49°42’33’’E, 490 m, 21.II.2005, fl. bud, Nusbaumer & Ranirison 2998 ( G); sous-préfecture de Vohemar , commune rurale de Daraina , forêt de Bobankora , partie nord, 13°13’29’’S 49°45’37’’E, 405 m, 29.I.2005, sterile, Nusbaumer & Ranirison 3005 ( G).

Figures

Fig. 1. – Rinorea ranirisonii Nusb. & Wahlert. A. Flowering branch; B. Inflorescence. [Ranirison 496, P] [Drawn by R. L. ndriamiarisoa]

Fig. 2. – Inflorescence of Rinorea ranirisonii Nusb. & Wahlert. [Ranirison 496, P] [Photo: P. Ranirison]

Fig. 3. – Map of Loky-Manambato area showing distribution of Rinorea ranirisonii Nusb. & Wahlert [Forest acronyms: Abd: Ambilondamba; Ank: Ankaramy; Apb: Ampondrabe; Atb: ntsahabe; Atd: Ambohitsitondroina; Atg: ntsaharaingy; Bek: Bekaraoka; Bin: Binara; Sol: Solaniampilana].