Memecylon arenicola R.D. Stone, 2022

Stone, Robert Douglas, 2022, Ten new species of Memecylon (Melastomataceae) from Madagascar, Candollea 77 (1), pp. 81-103 : 82-84

Memecylon arenicola R.D. Stone , sp. nov. ( Fig. 1).

H o l o t y p u s: MADAGASCAR. R e g. S AVA [Pro v. Antsiranana]: Vohémar, Anjiabe, Analabe E of Lac Sahaka , 13°04'54"S 49°54'26"E, 6.II.2008, fr., Stone et al. 2667 (CAS-1104135!; iso-: MO-6196936!, P [ P05206876 ]!, TAN!) .

Aff ine Memecyloni ambrensi Jacq.-Fél., sed ab eo foliis minoribus plerumque 4.5 –6.5 × 2.5– 3.5 cm (non usque ad 14 × 8 cm) et fructibus globosis (non ellipsoideis) differt.

Trees evergreen, c. 4 m high; young branchlets terete, c. 1.5–2 mm thick, surface smooth, ± rusty brown; older branchlets c. 3–4 mm thick, light brown, finely longitudinally fissured; nodes thickened; internodes (0.8–)1.3–3(–4.8) cm long. Leaves coriaceous, sessile, dull olive green on adaxial surface, pale brown on abaxial surface; blades elliptic, (3.5–)4.5–6.5(–7.5) × (2–)2.5– 3.5(–4) cm, base rounded to subcordate, apex rounded to retuse, obtuse or shortly and obtusely acuminate; midnerve finely canaliculate adaxially, somewhat prominent abaxially especially towards base of blade; transverse veins scarcely visible, c. 6 pairs, oriented at an oblique angle relative to midnerve, weakly prominent on adaxial surface, obscure abaxially, confluent with equally weak intramarginal nerves; margins revolute. Flowers unknown. Infructescences solitary at defoliated nodes of upper branchlets; peduncles stout, (0–) 1–2 mm long, sometimes extended by a short internode 1 mm long; bracts broadly triangular-cucullate, 0.75 mm long, early deciduous; fruiting pedicels 5.5–8 mm long, confluent with base of fruit. Fruits globose, c. 11 mm in diam.; persistent calycinal crown 1–1.5 mm high, 3 mm wide, margin sinuate-dentate; stylopodium prominent, ± filling the epigynous chamber.

Etymology. – The epithet arenicola is a compound derived from the Latin noun arēna meaning “sand” and the agent noun -cola meaning “inhabitor”. It functions as an adjective and means “sand-dweller”, in reference to the habitat in sandy soil.

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.

Conservation status. – Memecylon arenicola is known from a single location with an estimated AOO of 4 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 Fanamby ( GOODMAN et al., 2021). 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., 2021). The Lake Sahaka-Analabe littoral forest is nevertheless subjected to ongoing anthropogenic pressures including slashand-burn agriculture, removal of hardwood timber, pasturage of “zébu” cattle, and grassland fires which can sometimes penetrate into the forest ( RAKOTONDRAVONY, 2006; BIRDLIFE INTERNATIONAL, 2021; GOODMAN et al., 2021). Memecylon arenicola is thus provisionally assessed as “Critically Endangered” [CR B2ab(iii)] in accordance with the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Memecylon arenicola is strongly supported as sister to M. ambrense Jacq. -Fél. in molecular analyses (R.D. Stone, unpubl. data). These two species are also morphologically close, except that the leaves of M. arenicola are much smaller (see differential diagnosis), and the shape of the fruit is different (globose vs. ellipsoid). Another littoral species from Ambondrobe south of Vohémar, Memecylon longipes R.D. Stone (see below), has small leaves like those of M. arenicola and ellipsoid fruits like those of M. ambrense (differing from both of these species in having a calycinal crown that is conspicuously 4-dentate).

Sterile collections from higher-elevation forests of the Daraina region resemble Memecylon arenicola but have somewhat larger leaves: Nusbaumer & Ranirison 2345 (G), Nusbaumer L17-586 (G) and L22-150 (G). These populations need further study.

Additional specimens examined. – MADAGASCAR. Reg. SAVA [Prov. Antsiranana]: Vohémar, Nosy Be, Anjiabe , forêt littorale d’Analabe près du lac Sahaka , 13°04'43"S 49°54'04"E, 13. V .2004, fr., Razakamalala et al. 1236 ( CAS, MO, TEF) .