Memecylon aenigmaticum R.D. Stone, 2017

Stone, Robert Douglas, Mona, Imercia Gracious & Ramdhani, Syd, 2017, Revised treatment of Mozambican Memecylon (Melastomataceae-Olisbeoideae), with descriptions of four new species in M. section Buxifolia, Phytotaxa 331 (2), pp. 151-168 : 163-165

Memecylon aenigmaticum R.D. Stone , sp. nov. ( Fig. 6 )

Type:— MOZAMBIQUE. Cabo Delgado:Macomia district, Quiterajo, Namparamnera forest, elevation 136 m, 11°49'02.9"S, 40°20'31.7"E, 29 November 2008, Timberlake et al. 5574 (holotype K!, isotypes LMA, P!).

Evergreen shrub to 3 m high; young branchlets whitish grey, quadrangular, soon becoming terete with age; nodes thickened; internodes between normal leafy nodes 1–3.5 (–6.5) cm long. Leaves thickly coriaceous, on petioles 1–2 mm long; blades obovate, 1.75–3 × 1–1.75 cm, cuneate at base, rounded to obtuse at apex; only the midnerve clearly visible, impressed on the upper surface, ± prominent on the lower (especially toward the leaf base); intramarginal nerves and transverse veins ± obscure. Flowering cymes and flowers not seen. Fruits baccate, 1-seeded, solitary at the defoliated nodes of older branchlets, in the leaf axils and at the bracteate nodes alternating with those bearing fully developed leaves, borne on a very short, stout axis (length ca. 2 mm), pale green before maturity, elliptic to obovoid in outline, 9–10.5 × 7–8 mm, conspicuously verrucose-wrinkled; calycinal crown very short (ca. 0.3 mm high), margin sinuate to ± truncate.

Distribution and habitat: —Known only from the type collection made in Cabo Delgado Province, northern Mozambique ( Fig. 3 ). Coastal dry forest at 136 m elevation.

Phenology: —Flowers unknown; fruits in November.

Conservation status: — Memecylon aenigmaticum is known from a single location with an area of occupancy (AOO) of 4 km 2 (assuming a 4 km 2 grid cell size). Coastal forests in Cabo Delgado are virtually unprotected, and those in the Quiterajo vicinity are threatened by clearing for subsistence agriculture, logging of large timber trees and cutting of poles, and uncontrolled fires (Timberlake 2009, Timberlake et al. 2011). Memecylon aenigmaticum is thus provisionally assessed as Critically Endangered [CR B2ab(iii)] according to the IUCN Red List Categories and Criteria ( IUCN 2012).

Etymology: —The epithet aenigmaticum is an adjective based on the Greek noun ainigma meaning mysterious or difficult to interpret or understand. It is in reference to the fact that this new species has been previously confused with both M. natalense and M. rovumense (q.v.).

Discussion: — Memecylon aenigmaticum has been confused with the South African M. natalense but differs by its more thickly coriaceous leaves that are obovate in outline and rounded to obtuse at the apex (vs leaves thinly coriaceous, ovate in outline with apex acutely acuminate); by its cymes borne mostly at the defoliated nodes of older branchlets (vs cymes mostly axillary and at the bracteate nodes alternating with those bearing fully developed leaves); and by its ellipsoid to obovoid, verrucose-wrinkled fruits lacking a persistent calycinal crown (vs fruits ellipsoid to subglobose with smooth exterior and calycinal crown conspicuous) ( Table 1).

This new species appears closely related to M. rovumense , but differs by its much smaller leaves (1.75–3 × 1–1.75 cm vs 3.3–5.5 × 1.7–3.3 cm) and smaller, differently shaped fruits (ellipsoid to obovoid and 9–10.5 × 7–8 mm vs ovoid to broadly pyriform, 18 × 14 mm) ( Table 1).

Figures

FIGURE 3. Distribution of species of Memecylon section Buxifolia in Mozambique and adjacent parts of Malawi and Tanzania: M. incisilobum (black star); M. nubigenum (black triangles); M. rovumense (black circles); M. aenigmaticum (open diamond). Political boundaries are indicated by solid lines, and selected cities by open squares.

FIGURE 6. Memecylon aenigmaticum. A. Fruiting branch. B. Leaf. C. Fruit. (A–C from Timberlake et al. 5574, K). Drawing by Sandie Burrows.