Memecylon reductum R.D. Stone

Stone, Robert Douglas, 2022, Revised treatment of Memecylon section Buxifolia (Melastomataceae) in Madagascar, Candollea 77 (2), pp. 173-191 : 188

9. Memecylon reductum R.D. Stone , sp. nov. (F ig. 7B, 8).

Holotypus: MADAGASCAR. Reg. DIANA [Prov. Antsiranana]: Antsiranana II , Andrafiabe , Saharenana, lieu Andranomadio-Sahafary, 3 km au SE du village de Saharenana, 12°36'26"S 49°26'21"E, 27 m, 10.XI.2004, fr., Rakotondrajaona et al. 345 (P [ P05206947 ]!; iso-: MO-5902547 !, WAG [ WAG.1306064 ]!) .

Affine Memecyloni multinodi Jacq.-Fél., sed ab eo laminis foliaribus minoribus 0.35–0.55 × 0.3–0.45 cm late ellipticis vel suborbicularis (non 1.6–1.8 × 0.6–0.7 cm anguste ellipticis vel lanceolatis) ad basin late cuneatis vel rotundato-subcordatis (non cuneatis) ad apice obscure obtuso-acuminatis (non acutocuspidatis) differt.

Shrub 1 m high; branchlets slender, bark whitish gray; young branchlets compressed and dorso-ventrally 2-grooved, becoming subquadrangular and finally terete with age; nodes minutely thickened, internodes very short, c. 2 mm long, “aphyllous” nodes absent (all nodes bearing normal leaves). Leaves coriaceous, bright green and shining on the upper surface, paler beneath, minutely rugose on both surfaces when dry; petiole slender, c. 1 mm long; blades broadly elliptic to broadly ovate or suborbicular, 3.5– 5.5 × 3–4.5 mm, base broadly cuneate to rounded-subcordate, apex vaguely obtuseacuminate; midnerve faintly impressed adaxially, clearly visible but not prominent abaxially, intramarginal nerves and transverse veins obscure. Flowers unknown. Infructescences solitary in the leaf axils, unbranched; peduncles 1–1.5 mm long; additional axis (1–) 1.3–1.8 mm long; bracts rapidly deciduous, not seen. Fruits on pedicels 1(–1.5) mm long, subglobose to ± ellipsoid, 5.5–6 × 5–6 mm, purplish when ripe; persistent calycinal crown 1 mm high.

Etymology. – The epithet reductum refers to the very small leaves of this species.

Distribution and ecology. – Extreme northern Madagascar (DIANA region), known only from the type collection made on 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 at elevation c. 230 m.

Conservation status. – Memecylon reductum is known from a single location with an estimated AOO of 4 km ². The forest in this area has been severely degraded and evidently remains unprotected (RANAIVOARISOA et al., 2013). Memecylon reductum is thus provisionally assessed as “Critically Endangered” [CR B2ab(iii)] in accordance with the IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – This species clearly belongs to Memecylon sect. Buxifolia , sharing with M. multinode the character of lacking “aphyllous” nodes and differing by its unusually small leaves. It has previously been confused with the distantly related M. minimifolium , differing from that species by its whitish gray branchlets (vs. brownish), shorter internodes (2 vs. 3–5 mm), shorter petioles (1 vs. 1.5 mm), somewhat smaller leaves (3.5 – 5.5 × 3 – 4.5 vs. 6 × 4 mm), pedicels present, 1 –1.5 mm long (vs. absent, flowers sessile), and ± ellipsoid fruits (vs. subglobose). 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).