Memecylon leptophyllum R.D. Stone

Stone, Robert Douglas, 2022, Revised treatment of Memecylon section Buxifolia (Melastomataceae) in Madagascar, Candollea 77 (2), pp. 173-191 : 181-183

5. Memecylon leptophyllum R.D. Stone , sp. nov. (F ig. 3, 4).

H o l o t y p u s: MADAGASCAR. R e g. S AVA [Pr o v. Antsiranana]: sous-préfecture de Vohémar, commune rurale de Daraina, forêt d’Antsaharaingy , 12°54'15"S 49°39'26"E, 65 m, 27.II.2005, fl., Nusbaumer & Ranirison 1502 ( CAS-1105061 !; iso-: G [ G00019523 ]!, MO!, P!, TE F) .

Affine Memecyloni oblanceolato R.D. Stone, sed ab eo laminis foliaribus minoribus angustioribusque plerumque 4–5.2 × 0.5–0.9 cm (non 5.2–7.4 × 1.8–2.8 cm) ad marginem revolutis differt.

Shrubs c. 3.5 m high; bark of branchlets whitish gray; young branchlets ± compressed and laterally grooved then quadrangular; successive nodes alternately bearing normal leaves and floral bracts; internodes between normal leafy nodes 1–1.6(–2) cm long. Leaves coriaceous, dark green on adaxial surface, paler abaxially; petioles black, c. 5 mm long; blades narrowly elliptic or oblanceolate, (3.2–)4–5.2 × 0.5–0.9(–1.2) cm, base cuneate, apex acute-cuspidate, margins revolute; midnerve deeply impressed on adaxial surface, prominent abaxially; intramarginal nerves and transverse veins invisible. Cymules up to 8 mm long, 1-flowered, solitary in leaf axils, at intervening “aphyllous” nodes and also at uppermost leafless nodes; peduncles 0.5–1.5 mm long, additional axis 0.5–1.5 mm long; bracts narrowly triangular-acute, 0.75 mm long, early deciduous. Flowers on pedicels 0.75–1.25 mm long; hypantho-calyx yellowish green, campanulate to cupulo-patellate, 2 × 3 mm, margin shallowly sinuate-dentate, lobes broadly rounded, scarious-margined; corolla rounded-apiculate in bud; petals white, broadly elliptic, 2 × 2 mm, base truncate-subauriculate with claw 0.5 × 1 mm, apex acute; staminal filaments white, 6 mm long; anthers orange, dolabriform, 1.25 mm long, connective strongly incurved by dorsal oil-gland, thecae positioned at anterior end, posterior extremity obtuse; style white, 7 mm long; epigynous chamber with membranous interstaminal partitions forming a V-shaped structure beneath each petal scar. Fruits unknown.

Etymology. – The epithet leptophyllum is a compound derived from the Greek adjective leptós meaning “narrow” and the noun phúllon meaning “leaf ”. It functions as an adjective and means “narrow-leaved”.

Distribution and ecology. – Northeastern Madagascar (SAVA region), known only from the type collection made in the Antsaharaingy forested bloc, c. 33 km due north of the town of Daraina. Habitat in dry, semi-deciduous forest, at elevation c. 65 m.

Conservation status. – Memecylon leptophyllum is known from a single location with an estimated AOO of 4 km ². The Antsaharaingy forest where it occurs is a part of the Paysage Harmonieux Protégé de Loky Manambato gazetted in 2015 and managed by the Association F anamby (GOODMAN et al., 2018). Within Loky Manambato, the decline in area of dry forest was zero (0 %) between the years 1996 and 2006, and 330 ha (1.1 %) between 2006 and 2016 (GOODMAN et al., 2018). This species and its habitat are nonetheless subjected to ongoing anthropogenic pressures, e.g., by grassland fires which can sometimes penetrate into the forest (GOODMAN et al., 2018). Memecylon leptophyllum is thus provisionally assessed as “Critically Endangered” [CR B2ab(iii)] in accordance with the IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – Memecylon leptophyllum clearly belongs to Memecylon sect. Buxifolia , where it is seemingly close to the newly described M. oblanceolatum (see below). Not only are these two species separated geographically, there is also no overlap in the width of the leaves, those of M. leptophyllum being much narrower (0.5–0.9 vs. 1.8–2.8 cm wide) and with revolute margins. One photo of this species (F ig. 4A) shows a 5-merous flower, which is otherwise unknown in the genus Memecylon . However, this must be regarded as an aberrant form, because a second photo (F ig. 4B) shows two characteristically 4-merous flowers.