Memecylon linearifolium R.D. Stone, 2022

Stone, Robert Douglas, 2022, Ten new species of Memecylon (Melastomataceae) from Madagascar, Candollea 77 (1), pp. 81-103 : 92-94

Memecylon linearifolium R.D. Stone , sp. nov. ( Fig. 7 ).

Holotypus: MADAGASCAR. Reg. DIANA [Prov. Antsiranana]: Ambilobe, Marivorahona, village le plus proche Betsimiranjana , 13°02'35"S 49°09'15"E, 40 m, 15.VII.2005, fr., Rakotonandrasana et al. 928 ( P [ P05206870 ]!; iso-: NU!) .

Ob florem ignotum aff initatis incertae, sed a congeneris madagascariensibus mihi cognitis combinatione foliorum linearium 4–5.5 cm × 2–3(–4) mm et fructuum globosorum 7–9 mm diametro bene distincta.

Evergreen large shrubs or trees 4–5 m high; bark of branches pale brownish grey; ultimate branchlets slender, wiry, terete to subquadrangular; nodes thickened; internodes 1 –3 cm long. Leaves subcoriaceous, petiolate; petioles slender, 2 mm long; blades linear, ± plicately folded, 4–5.5 × 0.2–0.3(–0.4) cm, base attenuate and confluent with the petiole, apex obtuse; nervation obscure except for the midrib, which is visible abaxially and finely prominent towards the base of the blade. Flowers unknown. Infructescences solitary or geminate in the leaf axils and at the recently defoliated nodes; peduncles slender, 0.5–1.5 mm long, extended by a short internode 1–2 mm long; bracts deciduous, not seen. Fruits on pedicels 1–2 mm long, globose, 7–9 mm in diam.; calycinal crown appressed to the summit of the ovary.

Etymology. – The epithet linearifolium is a compound derived from the Latin adjective linearis meaning “linear” and the noun folium meaning “leaf ”. It functions as an adjective and means “linear-leaved”.

Distribution and ecology. – Northern Madagascar (DIANA Region), at the western edge of the Andrafiamena mountain chain, northeast of Ambilobe. Habitat in dry sclerophyllous or semi-deciduous forest at elevations of 40– 250 m.

Conservation status. – Memecylon linearifolium is known from two locations with an estimated AOO of 8 km ². Both of these locations are inside the western limit of the Paysage Harmonieux Protégé d’Andrafiamena Andavakoera (73,710 ha) managed by the Association Fanamby ( GOODMAN et al., 2021). Andrafiamena Andavakoera has sustained a major loss of 4,865 ha (28 %) of total forest cover between the years 1996 and 2016, although the areas of dry deciduous forest were less affected ( GOODMAN et al., 2021). Ongoing anthropogenic pressures include slash-and-burn agriculture (especially around mineral exploitation sites), destruction of forested habitat related to illegal gold mining and sapphire extraction, uncontrolled fires, exploitation of hardwoods, and collection of non-woody forest products ( GOODMAN et al., 2021). Based on its limited AOO and the apparent threats, M. linearifolium would meet the criterion B for listing as “Critically Endangered” in accordance with the IUCN Red List Categories and Criteria ( IUCN, 2012), but it might be better assessed as “Near Threatened” [NT], contingent on the continued effectiveness of habitat-specific conservation and management measures ( IUCN, 2019). The species is still poorly known, and we need better information on its local distribution, abundance, and microhabitat.

Notes. – The remarkably long, linear leaves of Memecylon linearifolium (greater than 15× longer than wide) will immediately distinguish this species from all others in the genus.

Additional specimens examined. – MADAGASCAR. Reg. DIANA [Prov. Antsiranana]: à 5 km à l’E du hameau Betsimiranjana, au lieu dit Andohanantsohihy, partie Sud , 13°02'42"S 49°09'53"E, 249 m, 3.VII.2005, fr., Leopold et al. 100 ( CAS, MO, P) .

Figures

Fig.7. – Memecylon linearifolium R.D. Stone. A. Fruiting branch; B. Leaf; C. Fruit. [A–C: Rakotonandrasana et al. 928, NU] [Drawing: S. Burrows]