Memecylon angustatum R.D. Stone

Stone, Robert Douglas, 2022, Revised treatment of Memecylon section Buxifolia (Melastomataceae) in Madagascar, Candollea 77 (2), pp. 173-191 : 178

3. Memecylon angustatum R.D. Stone , sp. nov. (F ig. 2).

H o l o t y p u s: MADAGASCAR. R e g. S AVA [Pr o v. Antsiranana]: Vohémar, Nosy be, Anjiabe, forêt d’Analabe, 13°04'14"S 49°53'40"E, 26.II.2003, fl., Rabevohitra et al. 4549 (P [P00516001]!; iso-: CAS-1065497!, G [G00074547]!, MO-4856428!, TE F!) .

Affine Memecyloni buxifolio Blume, sed ab eo laminis foliaribus tenuioribus subcoriaceisque plerumque latissimis supra medium (non in medio vel infra) basi plusminusve angustatis supra petiolum indistinctum (non basi cuneatis petiolis distinctis) differt.

Shrubs or small trees 1.5 –5 m high; branchlets slender, quadrangular when young, becoming terete with age; successive nodes alternately bearing normal leaves and floral bracts (these rapidly deciduous and not seen); internodes between normal leaves (0.6–)0.9 – 1.8(– 2.8) cm long. Leaves thinly coriaceous, bright green and shining on the upper surface, paler and dull on the lower, minutely granular-roughened on both surfaces when dry; blades elliptic to oblanceolate, mostly 2.7–3.8 × 1–1.7 cm, ± angustate at base and confluent with the petiole 1.5–3 mm long, generally cuneate-apiculate at apex but sometimes broadly and vaguely acuminate; only the midnerve clearly visible, finely to deeply impressed on the upper surface, ± prominent on the lower surface (especially toward the base); margins ± revolute. Cymules up to 1 cm long, 1–3(–5)-flowered, solitary in the leaf axils, at the intervening “aphyllous” nodes and also at the uppermost leafless nodes; peduncles 1–4(–4.8) mm long; additional axes 1–2.5 mm long; bracts narrowly triangular-acuminate, 1 mm long, cucullate, keeled on the back, soon deciduous. Flowers borne individually at the end of the inflorescence axes, on pedicels 0.5–1.5(–2) mm long; hypantho-calyx green, obconic to campanulate, 1.75– 2 × 2.75 mm, margin shallowly sinuate-dentate, lobes broadly rounded, scarious-margined; corolla rounded in bud; petals white, suborbicular, 2 × 2 mm, base truncatesubauriculate above the claw 0.5 × 0.5 mm, apex rounded and apiculate; stamens yellow, on filaments 4 mm long; anthers dolabriform, 1–1.25 mm long, the connective strongly incurved by the dorsal oil-gland, thecae positioned at the anterior end, posterior extremity obtuse; style 5 mm long. Fruits ellipsoid, 7– 10(–12) × 5–7.5 mm; persistent calycinal crown c. 1 mm high.

Etymology. – The epithet angustatum is an adjective meaning “narrowed”, in reference to the shape of the lower part of the leaf blades.

Distribution and ecology. – Northeastern coast of Madagascar (SAVA region), near the village of Anjiabe and lac Sahaka c. 34 km N of Vohémar. Habitat in littoral forest on sand, at elevation c. 25 m.

Conservation status. – Memecylon angustatum is known from a single location with an estimated EOO of <2 km ² and an AOO of 8 km ². As far as it is known, the entire population resides within the 3,000 ha Lake Sahaka-Analabe new protected area (NPA) and extension (BIRDLIFE INTERNATIONAL, 2021), which 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 littoral forest was zero (0%) between the years 1996 and 2006, and 135 ha (3.6 %) between 2006 and 2016 (GOODMAN et al., 2018). The Lake SahakaAnalabe littoral forest is nevertheless subjected to ongoing anthropogenic pressures including slash-and-burn agriculture, removal of hardwood timber, pasturage of “zébu” cattle, and grassland fires which can sometimes penetrate into the forest (RAKOTONDRAVONY, 2006; GOODMAN et al., 2018; BIRDLIFE INTERNATIONAL, 2021). Memecylon angustatum is thus provisionally assessed as “Critically Endangered” [CR B2ab(iii)] in accordance with the IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – Morphological and molecular analyses (STONE et al., 2017a) clearly place Memecylon angustatum in Memecylon sect. Buxifolia . Its “aphyllous” nodes and larger leaves distinguish it from M. multinode Jacq. -F él. The leaves are similar in size to those of M. buxifolium but differ in being thinly coriaceous and with base ± angustate (narrowed gradually and concavely) and confluent with the petiole. There is also a strong geographic separation between the two species ( M. buxifolium being widely distributed in dry forests of western Madagascar, the new species being restricted to littoral forest in the northeast).

The following collection from the Binara forest (Daraina region) appears close to Memecylon angustatum but remains unplaced to species pending further study: Gautier & Ravelonarivo 4064 (CAS, G, MO).

Additional specimens examined. – MADAGASCAR. Reg. SAVA [Prov. Antsiranana]: Vohémar , Nosy be, Anjiabe, Analabe, 13°04'43"S 49°54' 04"E, 11.V.2004, fr., Rabehevitra et al. 971 ( CAS, MO, P); Vohémar , Nosibe , Anjiabe, Anaborano près du Lac Sahaka, 13°04'42"S 49°54' 13"E, 25 m, 2.XI.2002, fr., Rabenantoandro et al. 1090 ( MO, P, TE F); Vohémar , Nosy be, Anjiabe, Analabe, 13°04'56"S 49°54'35"E, 24.II.2003, fr., Rabevohitra et al. 4527 ( CAS, G, MO, P, TE F); Vohémar , Nosibe, Anjiabe, village Anaborano, campement Andrainginalo, 10 km à l’E d’Anaborano, forêt d’Analabe, 13°04'09"S 49°54'08"E, 18 m, 11.X.2004, fl., Randrianarivelo et al. 151 ( CAS, MO); Vohémar , Nosy be, près du village d’Analabe et du lac Sahaka, 13°05'20"S 49°54'47"E, 10.VII.2003, fr., Razakamalala et al. 533 ( CAS, G, MO, P, TE F); Vohémar , Nosy be, Anjiabe, Analabe E of Lac Sahaka, 13°05'04"S 49°54' 03"E, 6.II.2008, fr., Stone et al. 2669 ( BR, CAS, K, MO, NU, P, TAN, WAG) .