Memecylon subchartaceum R. D. Stone 2020, sp. nov.
Creators: name: Stone, Robert Douglas
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Myrtales
Melastomataceae
Memecylon
Memecylon subchartaceum

description: Memecylon subchartaceum R.D. Stone, sp. nov. (Fig. 9).
Holotypus: MADAGASCAR. Reg. Anosy [Prov. Toliara]: forêt de Lakandava (station Jirama), 25.I.1990, fr., Rabevohitra 2207 (CAS-844951!; iso-: MO-3778128!, P [P05207253]!, TEF!).
Ob florem ignotum affinitatis incertae, Memecylon sabuloso Jacq. -Fél. et M. ivohibensi Jacq. -Fél. similis, sed ab eis laminae foliaris textura in sicco insolenter tenui fere papyracea bene distincta.
Evergreen shrub or tree 3– 7 m high; young branchlets very slender, sometimes wiry, subquadrangular to terete; older branchlets somewhat thickened at the nodes, blackish brown; internodes 0.5–2.0(–4.7) cm long, with intervening “aphyllous” nodes sometimes also present. Leaves thin, subchartaceous in dried material, bright green on the adaxial surface, slightly paler abaxially; petioles ± yellow, 0.5–2(–3) mm long; blades lanceolate to narrowly elliptic, (1.8–)2.7–5(–6.8) × (0.5–)0.7–1.2 (–1.9) cm, base narrowly cuneate, apex acute or ± acuminate, the acumen (4–)6–12(–18) mm; only the midnerve clearly visible, ± yellow, subprominent on adaxial and especially abaxial surfaces towards the base of the blade; intramarginal nerves very thin, faintly visible, ± prominent on both surfaces; transverse veins ± obscure or subprominent like the intramarginal nerves, oriented at an oblique angle relative to the midnerve. Flowers not seen. Fruits green, globose, about the size of a large pea; calycinal crown very short and somewhat membranous in texture; calyx margin 4-microdentate; epigynous chamber shallow; top of ovary nearly smooth (radial partitions very faint).
[A – B, E: Rabevohitra 2207, CAS; C: McPherson et al. 14893, CAS; D: Birkinshaw et al. 1614, MO] [Drawing: S. Burrows]
Etymology. – The adjectival epithet subchartaceum is in reference to the leaves of this species which are unusually thin-textured, almost papery.
Distribution and ecology. – Known from two localities in the Anosy region of southeastern Madagascar, just inland from the coastal city of Tôlan¨ aro (Fort-Dauphin) (Fig. 2). Habitat in humid forest below 300 m elevation.
Conservation status. – Memecylon subchartaceum has an EOO of 56 km ² and an estimated AOO of 12 km ² (assuming a 4 km ² grid cell size). The known subpopulations in the Lakandava and Bemangidy-Ivohibe forests are both presumably threatened by shifting agriculture (tavy), although the latter site may receive some degree of protection under a conservation agreement between the IUCN and the Rio Tinto mining company. Memecylon subchartaceum is thus provisionally assessed as “Endangered” [EN B2ab(iii)] in accordance with the IUCN Red List Categories and Criteria (IUCN, 2012).
Notes. – The flowers of M. subchartaceum are still unknown, and its affinity remains uncertain. It has been confused with M. sabulosum Jacq. -Fél., which occurs in the same vicinity and has leaves of a similar shape and size (narrowly lanceolate with dimensions 4.5 × 1.2 cm per description). However, in M. sabulosum the leaf-blades are dark green and ± rigidly coriaceous while in M. subchartaceum they are a paler green and unusually thin-textured. Memecylon ivohibense Jacq. -Fél. is also similar but in material of that species the leaves although narrowly lanceolate are smaller (dimensions 3 × 0.6 cm).
In comparison to the collections of M. subchartaceum from its type locality near Tôlan¨ aro (Fort-Dauphin), the material from Iabakoho notably differs in having somewhat longer internodes and larger leaves.
Paratypi. – MADAGASCAR. Reg. Anosy [Prov.Toliara]: Lakandava forest, 24°58'S 46°58'E, 25.I.1990, y.fr., McPherson et al. 14893 (CAS, K, MO, P, TEF);
Iabakoho, Antsotso Avaratra, Ivohibe, 24°34'17"S 47°12' 07"E, 21.V.2006, fr., Birkinshaw et al. 1614 (CAS, MO, P, TAN); village d’Antsotso Avaratra, forêt de Bemangidy, 24°35' 33"S 47°12'52"E, 22.V.2006, fr., Randriatafika et al. 656 (CAS, NU, P).
description: Published as part of Stone, Robert Douglas, 2020, New species of Memecylon (Melastomataceae) from Madagascar: treasures of the TEF Herbarium, pp. 219-239 in Candollea 75 (2) on pages 234-236, DOI: 10.15553/c2020v752a6, http://zenodo.org/record/5683759