Memecylon oblanceolatum R.D. Stone

Stone, Robert Douglas, 2022, Revised treatment of Memecylon section Buxifolia (Melastomataceae) in Madagascar, Candollea 77 (2), pp. 173-191 : 186

8. Memecylon oblanceolatum R.D. Stone , sp. nov. (F ig. 6, 7A).

Holotypus: MADAGASCAR. Reg. DIANA [Prov. Antsiranana]: forêt de Sahafary (bassin de la Saharenana), 7.II.1966, fl., Service Forestier 24506 (P [P00258012]!; iso-: CAS-1062098!, MO-4598292!, P [P00258013]!, TE F!, WAG [WAG.1923210]!).

Aff ine Memecyloni buxifolio Blume et M. amplifolio R.D. Stone , sed a primo laminis foliaribus majoribus plerumque 5.2–7.4 × 1.8–2.8 cm (non 2.2–4.1 × 1.0– 1.6 cm), a secundo ramulis juvenilibus quadrangularibus (non teretibus), laminis angustioribus (non 5.5–6.5 × 2.5–3.3 cm), ab ambobus laminis foliaribus oblanceolatis vel plus minusve ellipticis supra medium latissimis differt.

Shrubs or small trees 2.5– 3 m high; branchlets slender, ± quadrangular when young, becoming terete with age; successive nodes alternately bearing normal leaves and floral bracts (these early deciduous and not seen); internodes between normal leaves (0.6–)1.3–4.1(–8) cm long. Leaves coriaceous, dark green and shining on adaxial surface, paler and dull abaxially, drying brownish and minutely granular-rugose on both surfaces; petioles 1.5–3 mm long; blades broadly oblanceolate (when ± elliptic, then definitely widest above middle), (4.4–) 5.2–7.4(–8.9) × 1.8–2.8(–3.5) cm, attenuate at base, generally cuneate and acute at apex but sometimes rounded-obtuse or vaguely broad-acuminate; only midnerve clearly visible, finely impressed on adaxial surface; one pair of lateral nerves faintly visible on both surfaces, course curvilinear and 1–3 mm from margin in basal half of blade; transverse veins obscure. Cymules up to 1.2 cm long, 1–3-flowered, solitary or geminate in leaf axils, at intervening “aphyllous” nodes and also at uppermost leafless nodes; peduncles 0.5–3(–6) mm long; additional axes 0.5–3 mm long; bracts triangular-acute, to 1 mm long, early deciduous. Flowers borne individually at ends of inflorescence axes, on pedicels 0.3– 1.5 mm long; hypantho-calyx green, obconic to cupulo-patellate, 1.75– 2 × 2.5–2.75 mm, margin shallowly sinuate-dentate, lobes broadly rounded, scariousmargined; corolla rounded-apiculate in bud; petals white, suborbicular, 2 × 2 mm, base truncate-subauriculate with claw 0.5 × 0.5 mm, apex rounded and apiculate; staminal filaments white, 4 mm long; anthers yellow, dolabriform, 1.25 mm long, connective strongly incurved by dorsal oil-gland, thecae positioned at anterior end, posterior extremity obtuse; style white, 6–7 mm long; epigynous chamber deep, with membranous interstaminal partitions forming a V-shaped structure beneath each petal scar. Fruits ellipsoid, 6 × 5 mm; persistent calycinal crown 1 mm high.

Etymology. – The epithet oblanceolatum is an adjective referring to the shape of the leaves, i.e., more than twice as long as wide and with the widest part above the middle.

Distribution and ecology. – Extreme northern Madagascar (DIANA region), known only from the Sahafary plateau c. 33 km southeast of the city of Antsiranana and east of the Route nationale no 6 at Andranomena Antsiranana. Habitat in dry, deciduous forest on sand, at elevations of 200– 280 m.

Conservation status. – Memecylon oblanceolatum is known from a single location on the Sahafary plateau and has an estimated EOO of 2 km ² and an AOO of 12 km ². The forest in this area has been severely degraded and evidently remains unprotected (RANAIVOARISOA et al., 2013). Memecylon oblanceolatum is thus provisionally assessed as “Critically Endangered” [CR B2ab(iii)] in accordance with the IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – Memecylon oblanceolatum is placed in Memecylon sect. Buxifolia based on the results of morphological and molecular analyses (STONE et al., 2017a; R.D. Stone, unpubl. data). This population from extreme northern Madagascar (Sahafary forest) was previously included by JACQUES- F ÉLIX (1985b) in his concept of M. perrieri . However, M. perrieri is now treated as a taxonomic synonym of M. buxifolium Blume (STONE, 2014), which as presently circumscribed is a morphologically variable species with a wide distribution in the dry forests of western and northern Madagascar. Memecylon oblanceolatum is geographically separated from M. buxifolium and also differs from that species by the larger size and unusual shape of its leaves. It differs from M. amplifolium in having young branchlets quadrangular (vs. terete) and leaf blades broadly oblanceolate and attenuate at the base (vs. broadly obovate to elliptic and cuneate).

The following collections are close to Memecylon oblanceolatum but are from outside the type region and remain unplaced to species pending further study: Gautier et al. 4598 (G, K, MO, P) and Rakotondrafara et al. 403 (G, MO, P).

Additional specimens examined. – MADAGASCAR. Reg. DIANA [Prov. Antsiranana]: forêt de Sahafary, 12°36'26"S 49°26' 43"E, 280 m, 8.I.2007, fr., Ratovoson et al. 1225 ( CAS, MO, P) ; ibid. loco, 12°35' 17"S 49°26'05"E, 210 m, 15.II.2005, fl., Schatz et al. 4320 ( MO) ; ibid. loco, 7.II.1966, fl., Service Forestier 24494 (P, TE F) ; ibid. loco, 12°35'02"S 49°26' 59"E, 200 m, 6.II.2007, fl., Stone et al. 2620, 2622, 2624 ( CAS, G, K, MO, P, TAN) .