Marsdenia mayottae W.D. Stevens, Labat & Barthelat, 2016

Stevens, W. Douglas, Labat, Jean-Noël & Barthelat, Fabien, 2016, Two new species of Apocynaceae, Asclepiadoideae from Mayotte, Candollea 71 (1), pp. 127-134 : 128-131

Marsdenia mayottae W.D. Stevens, Labat & Barthelat , spec. nova ( Fig. 1 , 2 ).

Typus: M AYOTTE: Grande Terre, Bandré , Rassi Abambo , 9.II.2001, Barthelat, M’Changama & Ali Sifari 295 (holo: P [ P00229277 ]!; iso: G!, K!, MAO!, MO!, P [ P00282507 ]!) .

Marsdenia mayottae W.D. Stevens, Labat & Barthelat is most similar to M. vohiborensis Choux , but differs from this species by its umbonate style apex completely covered by the terminal anther appendages and the absence or near absence of a corona.

Shrub or twining vine, woody but apparently not corky, underground parts unknown, stems densely appressedpuberulent, sparsely lenticellate, internodes 1-6 cm; latex white. Leaves opposite; blades 6.5-11.1 × 4-9.2 cm, ovate to elliptic, glabrous or puberulent on veins below; apex acuminate to attenuate; base truncate to shallowly lobate, its sinus up to 5 mm deep, lateral veins 4 to 6, colleters 10 to 24; petiole 2.4-5.5 cm, sparsely puberulent. Inflorescences solitary, paniculate with 2 to 6 congested-racemose, appressedpuberulent branches; peduncle (3) 10-48 mm; fertile axes up to 3 cm long, more or less covered with pedicel scars. Flowers borne on pedicels 4–9 mm long; bracts numerous and conspicuous, 1.5-10 × 0.6-4 mm, elliptic to spathulate, sometimes leaf-like; calyx with 1 colleter below each sinus within, lobes elliptic to ovate with round tips, unequal, 3-4 × 1.7-2 mm, sparsely puberulent along axis abaxially, not ciliolate, green; corolla shallowly campanulate, dull yellow, without calli, barbate in distal half of tube and proximal half or more of each lobe adaxially, glabrous abaxially, tube 1.7-2.3 mm, lobes elliptic with tip rounded, 2.2-3 × 1.6- 1.7 mm, patent; corona lobes absent or if present reduced to a fleshy tooth adnate to base of anther, deltate, up to 0.4 mm long, 0.2 mm wide at base; gynostegium nearly sessile, guide rails 0.7 mm long, slightly salient at base; anthers trapezoidal, nearly rectangular, 0.8-1 × 0.8-1 mm, terminal appendages 0.6 × 0.6 mm, elliptic to ovate, translucent, corpusculum ellipsoid to subsagittoid, 0.19-0.28 × 0.08-0.13 mm, translators flat, 0.19-0.25 × ca. 0.05 mm, pollinia ellipsoid to obovoid, 0.39-0.43 × 0.24-0.3 mm;

style apex umbonate, 1.4-1.5 mm wide at base. Follicles narrowly ovoid with asymmetrical base, 7.5-9.5 × 2.5-3.5 cm, smooth, glabrous, follicle wall 5-7 mm thick; seeds elliptic, 8-11 × 5-7 mm, dark grey-brown with red-brown mottling, margin 0.6-0.7 mm wide, distally entire or inconspicuously crenulate, surface smooth, coma 3.5-4 cm long, white.

Distribution, habitat and phenology. – Marsdenia mayottae is only known from Mayotte, where it can be found at low elevations (less than 10 m a.s.l.) in littoral forest growing with Thespesia populnea (L.) Sol. ex Corrêa, Xylocarpus granatum Koenig , Mimusops comorensis Engl. , Maytenus undata (Thunb.) Blakelock and Calophyllum inophyllum L. It is also found on coastal squeletic soils on basaltic rock or in dry littoral scrubland with Grewia picta Baill. , G. triflora (Bojer) Walp. , Guettarda speciosa L. and Maytenus undata . In addition, it can be found also on calcareous sand soil with Talipariti tiliaceum (L.) Fryxell. The new species is very rarely present also in dry lowland forest on other substrates at up to 100 m.

Marsdenia mayottae has been recorded in flower from November to January and in fruit in May and June.

Vernacular names and local use. – The following vernacular names in Shibushi have been recorded for M. mayottae by Barthelat & Boullet (2005) or on herbarium labels: “Pamba suisui be” or “Pamba suisui famakitrano”, “Macarangana vahi”, “Vahy rotono”, “Vahy maro” and “Kidoro voalavo”. The plants are used in the preparation of magic potions known as “grigris” (M. M’changama, pers. comm.).

Conservation status. – Marsdenia mayottae is only known from highly threatened littoral and lowland dry forests on Mayotte, and its population, as currently known, is highly fragmented. It is only known from five locations despite intensive inventories in the last decades. Thus, its preliminary risk of extinction can be assessed as “Endangered” [EN B2ab(iii)] following the IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – This species shares a dense, bracteate inflorescence with M. vohiborensis Choux from the central plateau of Madagascar. However, M. vohiborensis has a long-exserted style apex while M. mayottae has an umbonate style apex completely covered by the terminal anther appendages. The absence or near absence of a corona in M. mayottae is unique among the species of Marsdenia of Madagascar and the Comoros, and rare in the genus.

Paratypi. – M AYOTTE: Grande Terre , Saziley, 17.I.2001, Barthelat & Ali Sifari 233 ( G, K, MAO, MO, P); Petite Terre , Labattoir, Plage de Moya, 15.I.2002, Barthelat & Ali Sifari 694 ( K, MAO, MO, P); ibid. loc., 15.I.2002, Barthelat & Ali Sifari 699 ( MAO, MO, P); Grande Terre , Mliha, Mtsumbatsu, 20.XII.2001, Barthelat et al. 625 ( MAO, MO, P); sommet du Bouzi, X.1850, Boivin s.n. ( P); Rassi Maoussi , 17.V.1999, Mas 176 ( P); Sohoa , 28.VI.1997, Pascal 942 ( G, MO, P) .

Figures

Fig. 1. – Marsdenia mayottae W.D. Stevens, Labat & Barthelat. A. Habit;B. Gynostegium; C. Pollinarium. [Barthelat et al. 295, P] [Drawing: A. Arbeláez]

Fig. 2. – Field pictures of the new species Marsdenia mayottae W.D. Stevens, Labat & Barthelat. [Photos: F.Barthelat]