Memecylon minutifolium R.D. Stone

Stone, Robert Douglas, 2022, Revised treatment of Memecylon section Buxifolia (Melastomataceae) in Madagascar, Candollea 77 (2), pp. 173-191 : 183-184

6. Memecylon minutifolium R.D. Stone , sp. nov. (F ig. 5).

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’Ambilondomba , 13°09'52"S 49°38'49"E, 360 m, 26.I.2004, fl. buds, Ranirison, Nusbaumer & Wohlhauser 308 ( CAS-1104898 !; iso-: G [ G00028156 ]!, MO!, P!, TAN) .

Affine Memecyloni multinodi Jacq.-Fél., sed ab eo foliis multo minoribus 5–7 × 2– 2.5 mm (non 16– 18 × 6– 7 mm) facile distinguitur.

Shrubs 2– 3.5 m high; bark of branchlets whitish gray; young branchlets quadrangular and narrowly alate; internodes short, 2–15 mm long, “aphyllous” nodes virtually absent (most nodes bearing normal leaves). Leaves coriaceous, bright green and shining on adaxial surface, paler and dull abaxially, minutely rugose on both surfaces in dried material; petioles slender, short but distinct, 1 – 1.5 mm long; blades narrowly elliptic, 5 –7 × 2– 2.5(–3) mm, base cuneate, apex acute-cuspidate, margins revolute; midnerve invisible on adaxial surface, slightly visible and not prominent abaxially. Cymules up to 1 cm long, 1-flowered, solitary in leaf axils, at intervening “aphyllous” nodes and also at uppermost leafless nodes; peduncles (0.75–)1.25–2.5(–3) mm long; additional axis (1.25–)1.5–2.25(–2.5) mm long; bracts early deciduous, not seen. Flowers subsessile or on slender pedicels to 0.75(–1) mm long; hypantho-calyx obconic to narrowly campanulate, 2 × 2 mm, margin shallowly sinuate-dentate, lobes broadly rounded, scarious-margined; corolla in bud obconic, apex obtuse; open flowers not seen. Anthers c. 1 mm long, thecae positioned at anterior end, dorsal oil-gland present. Fruits ± elliptic, 5 × 4 mm; persistent calycinal crown c. 0.75 mm high.

Etymology. – The epithet minutifolium is a compound derived from the Latin adjective minutus meaning “very small” and the noun folium meaning “leaf ”. It functions as an adjective and means “very small-leaved”.

Distribution and ecology. – Northeastern Madagascar (SAVA region), known only from the Ambilondambo and Ampondrabe forested blocs, c. 5–25 km north of the town of Daraina. Habitat in transitional to dry, semi-deciduous forests, at elevations of 125– 360 m.

Conservation status. – Memecylon minutifolium is known from two locations with an estimated AOO of 8 km ². The Ambilondambo and Ampondrabe forests are both 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 including slash-and burnagriculture, removal of hardwood timber, pasturage of “zébu” cattle, and grassland fires which can sometimes penetrate into the forest (RAKOTONDRAVONY, 2006; GOODMAN et al., 2018). Memecylon minutifolium is thus provisionally assessed as “Endangered” [EN B2ab(iii)] in accordance with the IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – Memecylon minutifolium clearly belongs to Memecylon sect. Buxifolia , where it appears most closely related to M. multinode . Both of these species have acutecuspidate leaves and lack the character of “aphyllous” nodes shared by other members of this species-group (STONE, 2014).

The extremely small leaves of Memecylon minutifolium are its most distinctive character. The paratype collection Ratovoson et al. 1078 cited below was initially identified as M. minimifolium H. Perrier , which has similarly small leaves but of a very different shape [c. 6 × 4 mm, broadly ovate to elliptic or nearly orbicular with apex rounded vs. 5 – 7 × 2 – 2.5(– 3)] mm, narrowly elliptic with apex acutecuspidate in M. minutifolium ). Molecular analyses further indicate that M. minimifolium belongs to the Malagasy clade sensu STONE (2014) and is not a member of Memecylon sect. Buxifolia (R.D. Stone, unpubl. data).

Additional specimen examined. – MADAGASCAR. Reg. SAVA [Prov. Antsiranana]: Vohémar , Ampisikinana, Tsaratanana, Ambarilao, forêt d’Ampondrabe Antsiraka, 5 km à l’W d’Ambarilao, 12°58'26"S 49°41' 50"E, 125 m, 6.XI.2005, fr., Ratovoson et al. 1078 ( G, MO, P) .