Memecylon mayottense R.D.Stone, 2006

Stone, Robert Douglas, 2006, New species of Memecylon L. and Warneckea Gilg (Melastomataceae) from Madagascar and Mayotte, Adansonia (3) 28 (2), pp. 337-358 : 352-354

Memecylon mayottense R.D.Stone , sp. nov.

( Fig. 9 )

Species in insula dicta “ Mayotte ” endemica a congeneribus madagascariensis combinatione ramulorum juvenium quadrangularium vel quadrialatorum, foliorum brevipetiolatorum cum laminis coriaceis 4-6 cm longis 2-3.3 cm latisque, cymularum umbellatarum ad nodos strumosos ramulorum vetustiorum, bractearum squamatarum persistentiumque, corollarum albarum in alabastro rotundatarum, antherarum cum connectivo dorsaliter glanduloso, fructuum subglobosorum 15 mm diametro diversa.

TYPUS. — Mayotte. Sohoa , 12°48’39”S, 45°06’20”E, 19.IV.1999, Pignal 1216 (holo-, P, barcode no. 176742; iso-, B, BR, K, MA, MO, PR).

PARATYPES. — Mayotte. Dapani , 17. I .1996, Pascal 343 ( K, P). — Sohoa, alt. 200 m, 2.IV.1996, Pascal 449 ( G, K,

MO, P, WAG). — Dapani , alt. 200 m, 23.X.1996, Pascal 735 ( CAS, G, K, MO, P, WAG). — Dapani, alt. 150 m, 11.II.1997, Pascal 888 ( P). — Grande Terre, Kani Kéli, bas du GR Choungui , 11.IX.2001, Pignal et al. 1878 ( G, K, MO, P, herb. Mayotte) . — Grande Terre, Choungui, côté hors du GR, 21.IX.2001, Pignal et al. 1920 ( G, P, herb. Mayotte) . — Grande Terre , Réserve forestière de Sohoa, 10.XI.2001, Barthelat & M’Changama 541 ( K, MO, P, herb. Mayotte) . — Grande Terre , road leading to summit of Mont Choungui, 3.III.2004, Barthelat et al. 1314 ( P, herb. Mayotte) .

DESCRIPTION

Evergreen shrub or small tree 2-12 m high; branchlets quadrangular and sometimes narrowly 4-winged when young, becoming terete with age and swollen at the nodes; internodes 1-4 cm long; bark whitish. Leaves coriaceous and ± discoloured, dark green and shining on the upper surface, paler or yellowish and dull on the lower, finely granular-rugose on both surfaces (when dry); petioles 1-3 mm long; blades mostly broadly ovate-elliptic, 4-6 cm long, 2-3.3 cm wide, rounded at the base and abruptly narrowed above the petiole, rounded and often retuse at the apex, varying to narrowly elliptic and broadly and obtusely short-acuminate at apex or even cuneate-oblanceolate to -obovate; mid-nerve impressed on the upper surface, prominent on the lower (especially toward the base); transverse veins occasionally visible on the lower surface, oriented at an oblique angle relative to the midnerve, ± regularly spaced at intervals of c. 4 mm; margins slightly and narrowly revolute. Cymes umbelliform, c. 1.5 cm long, (1-)3-7-flowered, in fascicles of 1-3(-4) at the nodes below the current leaves; peduncles mostly 5-7 mm long, quadrangular or narrowly 4-winged; bracteoles triangular-ovate, apiculate, c. 0.8 mm long, persistent. Flowers on pedicels c. 3 mm long; hypantho-calyx campanulate, 2.5 mm long, 3.5 mm wide, the margin slightly scarious and 4-sinuate. Corolla ± rounded in bud; petals white, broadly ovate-deltate, 3 mm long, 2.5 mm wide, with conspicuous mid-nerve, apex ± acute, base auriculate and broadly shortunguiculate. Anthers c. 1.3 mm long, the connective narrowly conic-acute and strongly incurved around the large, elliptical gland, this occupying about half the length on the dorsal side; pollen sacs lateral (anterior); filaments dark violet, 5 mm long. Style c. 6 mm long. Fruits subglobose (sometimes ± asymmetrical), dark-mottled becoming violet at maturity and 17 mm long, 15 mm wide; calycinal crown c. 1 mm long, slightly spreading or ± erect; epigynous chamber rather shallow, lacking partitions.

REMARKS

Sequences from the ITS and ETS regions of nuclear ribosomal DNA, obtained from the type material, indicate that M. mayottense belongs to the Madagascan clade and is not closely related to the east-African species (R. D. Stone unpubl. data). Yet among the known Madagascan species its affinities are not clearly evident. In Jacques-Félix (1985a), M. mayottense would key to the group that includes M. infuscatum , M. louvelianum H.Perrier , and M. dalleizettei H.Perrier , on account of the dorsal gland on the anther connectives and the cymules with several pairs of imbricated, persistent bracts. It appears most similar to M. louvelianum , in particular to the atypical form with coriaceous, rounded leaves and larger fruits that has been collected several times on calcareous substrates in Antsiranana and Mahajanga provinces (Rakotovao RN-6153, MO, P; SF-10670, P; Bardot-Vaucoulon 900, 973, P). Memecylon louvelianum notably differs from M. mayottense in its terete branchlets, shorter peduncles, somewhat smaller flowers with corolla narrowly acute-acuminate in bud, violet petals, and ellipsoid fruits with a cushion-like peristyle inside the calicinal crown.

Figures

FIG. 9. — Memecylon mayottense R.D.Stone: A, habit; B, leaf (adaxial view); C, inflorescence with flower buds; D, petal; E, stamen; F, fruit. A, Pascal 888; B, Pascal 449; C-E, Pignal 1216; F, Pascal 735. Scale bars: A, 5 cm; B, 2 cm; C, 3 mm; D, E, 1 mm; F, 5 mm.