Catharanthus makayensis L. Allorge, Phillipson & Razakamal., 2015

Allorge, Lucile, Phillipson, Peter B. & Razakamalala, Richardson, 2015, Catharanthus makayensis L. Allorge, Phillipson & Razakamal. (Apocynaceae), a new species from Madagascar, Candollea 70 (1), pp. 61-66 : 65-66

Catharanthus makayensis L. Allorge, Phillipson & Razakamal. , spec. nova ( Fig. 2 A-D).

Typus: MADAGASCAR. Prov. de Toliara: Atsimo-Andrefana Region, Forêt d’Anosilamy , Fokontany Beronono , Commune Beronono , 21°20’30”S 45°10’53”E, 448 m, 13.I.2010, Razakamalala, Rakotovao & Andriantiana 5155 (holo-: MO [ MO-2282216 ]!; iso-: P, TAN!) .

Differs from all other species by its hexangular stems, stems and leaves with a distinctive puberulent indument, and flowers with its long filiform recurved sepals and corolla with white lobes and a deep magenta eye.

Perennial herb to 50-60 cm tall, with sparse white latex. Stems hexagonal-costulate, the ridges most pronounced towards the base, puberulent at least when young, pustulate at the base; internodes ca 3 cm long at the base of the stem, and 2 cm long above. Leaves opposite; petiole 2 mm long; limb narrowly elliptic, 3.2-3.8 × 1.2-1.5 cm, mucronate, sub-coriaceous, puberulent; veins pale yellow when fresh (drying brown-green), secondary veins 6-8 sub-opposite pairs, clearly visible on the abaxial and adaxial sides, forming an angle of 30-35 to the midrib; mucro 1 mm long. Inflorescence pseudo-axillary, present in the axil of one leaf of a leaf-pair, usually comprising two flowers lacking a common peduncle and developing sequentially, occasionally reduced to a solitary flower. Flowers erect, shortly pedicellate; pedicels 1-2 mm long; calyx with curved filiform sepals, 5-6 mm long; corolla tube very slender, 2.8 to 3 cm long, 0.8 mm diameter, somewhat swollen in the throat 2-3 mm below the mouth, magenta; corolla propeller-like, lobes highly assymetrical, 2 × 1 cm, white shading abruptly to magenta at the base. Fruit comprising two erect follicles, 20 mm × 2 mm, containing 3-4 brown seeds.

Geographic distribution and habitat. – Catharanthus makayensis is only known from two collections made within the Makay Massif, an area of sandstone situated to the north of the Mangoky River and to the south-east of the city of Morondava. The plants were observed growing in sandy ground on riverbanks, and moist areas among rocks, at elevations of 400-600 m. The Makay region has been only very poorly explored, but recently the first serious attempts to conduct biological inventory have been made in the massif, thanks to the efforts of the NGO “Naturevolution” (http://www.naturevolution.org) and the production of a film in 2011 (“Makay, les aventuriers du monde perdu”) by GEDEON PROGRAMMES (2015) and a book ( WENDENBAUM, 2011) about this work.

Conservation status. – Catharanthus makayensis is currently known from only two localities approximately 20 km apart in the Makay Massif, an area that has been only very poorly explored. Our observations in the field suggest that it is not common in the massif, although further exploration in suitable habitats would almost certainly reveal additional localities for the species. The area is remote from habitation and is currently subject to little impact from grazing or other human-induced impacts. Nevertheless the Makay Massif lacks legal protection, and proposed mining projects in the area may impact the species in the future. It is impossible to reliably estimate the Extent of Occurrence of the species on the basis of the data currently available, but based on the two known locations an estimated Area of Occupancy of ca. 8 km 2 can be calculated for the species. With no immediate threats to the survival of the two known sub-populations of C. makayensis , and until more information on the distribution of the species becomes available it is best assessed as “Vulnerable” [VU D2] following IUCN Red List Categories and Criteria ( IUCN, 2012).

Phenology. – Catharanthus makayensis has been observed in flower and in fruit in August, November and January.

Note. – Catharanthus makayensis differs from all other species by its stems which are distinctly hexagonal in crosssection, a characteristic which is most easily observed in fresh material. Other species of Catharanthus are either quadrangular-winged in C. ovalis and C. trichophyllus , or cylindrical (sometimes with shallow longitudinal ridges) in all the other species. The new species can also be distinguished from other species of the genus by certain characters of the flowers, notably by its 5-6 mm long filiform sepals which are clearly much narrower and longer than for all the other species, with the only exception of C. coriaceus , but the latter species is highly distinct with its pendulous fruits, as opposed to the erect fruits of C. makayensis and all other species. Together with C. roseus , C. makayensis is the only species to have a magenta eye, rather than white to pale yellow in all the other species, however, the corolla lobes and the flower bud of C. makayensis are pure white (or possibly slightly pale pink tinted) ( Fig. 2A, D ) and C. roseus typically has pink lobes ( Fig. 2E ). Certain forms of C. roseus have a predominantly white corolla, but this is coupled with a white or pale yellow eye as far as is known in wild populations ( C. roseus var. albus ). Horticultural forms of C. roseus are available with a diversity of colours, including some that closely resemble C. makayensis . Two other species of Catharanthus have been collected just to the south and/or north of the Makay Massif: C. ovalis Markgr. and C. scitulus (Pichon) Pichon , but they have not yet been recorded within the massif itself.

Paratypi. – MADAGASCAR. Prov. de Toliara: Atsimo-Andrefana Region. Makay Massif . Along a tributary of Menampandaha River , 21°12’56”S 45°19’07”E, 480 m, 22.XI.2010, Phillipson, Andriantiana & Rakotovao 6174 ( TAN).

Figures

Fig. 2. – Living plants in situ of Catharanthus makayensis L. Allorge, Phillipson & Razakamal. (A-D) and C. roseus (L.) G. Don (E). A. Branch with inflorescence; B. Inflorescence with sideview of flower and young fruits; C. Flower bud showing bumps in corolla tube over the stamens and stigma; D. Detail of stems, showing the angles, petiolate leaves and persistent calices; E. Topview of flower. [Photos:A -B: Peter Phillipson; C-D: Bruno David; E: Lucile Allorge]