Memecylon pseudogaleatum R.D. Stone, 2020

Stone, Robert Douglas, 2020, New species of Memecylon (Melastomataceae) from Madagascar: treasures of the TEF Herbarium, Candollea 75 (2), pp. 219-239 : 232-234

Memecylon pseudogaleatum R.D. Stone , sp. nov. ( Fig. 8 ).

Holotypus: MADAGASCAR. Reg. Atsimo-Atsinanana [Prov. Fianarantsoa]: distr. Farafangana, village Amporoforo , lieu de récolte Boma, 18.II.1955, fl. & fr., Service Forestier 15244 ( TEF!) .

Aff inis Memecylon galeato H. Perrier sed ab eo ramulis juvenilibus subquadrangularibus teretibusve (non compressis), floribus minoribus hypanthio post anthesin 3–4 × 5.5–7 mm (non 4–5 × 8–11 mm) petalis 4–5 × 4–5 mm obcordatis (non 9 × 7 mm late ovatis) atque fructu bilateraliter asymmetrico differt.

Evergreen tree 21 m high, trunk 14 m, d.b.h. 0.5 m; bark fissured; branchlets robust, the youngest subquadrangular to terete; nodes thickened; internodes (3.6–)4.2–5.9(–7) cm long. Leaves coriaceous, slightly granular on both surfaces (in dried material), bright green and moderately shining on the adaxial surface, bronzed abaxially; petiole robust, 2 – 4 mm long; blades elliptic, (6.7–)7.2–9.2(–9.9) × 3.1–4.3(–5) cm, cuneate to angustate at base, ± broadly acuminate at apex, acumen ± acute; only the midnerve clearly visible, finely impressed on the adaxial surface, somewhat prominent abaxially especially towards the base of the blade; transverse veins scarcely visible, ± prominent on the adaxial surface in dried material, oriented at an oblique angle relative to the midnerve, joined to the similarly weak lateral nerves 1–2 mm from the margin. Cymes 1-flowered, solitary or geminate in the leaf axils; peduncle robust, 2–3(–7) mm long; bracts and bracteoles c. 2 mm long, the former narrowly triangular, keeled on the back, the latter navicular-cucullate, ± clasping the base of the flower. Flowers ± sessile (true pedicel absent or nearly so); calyx completely covering the corolla in bud and detaching irregularly at anthesis (sometimes remaining attached to one side); hypanthium cupuliform, 3–4 × 5.5–7 mm, margin ± truncate; petals thick, obcordiform, 4–5 × 4–5 mm, base broadly clawed, apex sharply acute; stamens dolabriform, anthers 4 mm long, thecae frontoventral; connective slightly incurved by the median gland, posterior extremity of connective narrowly conical-acuminate, extending 2 mm past the gland; filaments c. 5 mm long; style c. 13 mm long; epigynous chamber deep, with conspicuous scars at the points of attachment of the staminal filaments and especially of the petals, and with 8 membranous interstaminal partitions radiating from the stylar scar in a cruciform pattern, each partition extending past the petal-scar as a triangular appendage c. 0.5 mm long. Fruits 17–18 × 21–22 mm, developing asymmetrically with the base somewhat gibbous and the apex correspondingly displaced to the opposite side; calycinal crown thick, ± truncate, 1–2 mm high.

Etymology. – The adjectival epithet pseudogaleatum is in reference to the earlier confusion of this species with the closely related M. galeatum (see Notes).

Distribution and ecology. – Known only from near Amporoforo, c. 10 km inland from Madagascar’s southeastern coast between the towns of Vohipeno and Farafangana ( Fig. 2 ). Habitat in remnants of humid forest on laterite, elevation c. 25 m.

Conservation status. – Memecylon pseudogaleatum is known from a single location with an AOO of 4 km ². Given that the forests of the coastal region around Farafangana have been largely destroyed or reduced to small remnants, and that M. pseudogaleatum has not been seen in more than 60 years, it is quite possible that the species is already extinct, although additional field-work would be needed to verify this. Memecylon pseudogaleatum is thus provisionally assessed as “Critically Endangered” [CR B2ab(iii)] in accordance with the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Memecylon pseudogaleatum and M. galeatum are clearly very close, as evidenced by the fact that the flowering specimen Service Forestier 15244 (TEF), designated here as the holotype of the new species, was previously annotated by R. Capuron as an unnamed variety of the latter. Compared with typical M. galeatum , the material of M. pseudogaleatum differs in having young branchlets subquadrangular to terete (not compressed and laterally grooved on the two faces), smaller flowers with petals obcordate (vs. broadly ovate), and fruits bilaterally asymmetrical (in this respect more similar to M. bezavonense and the newly described M. convergens , q.v.). The type locality of M. pseudogaleatum at Amporoforo is also disjunct by 375 km from the nearest known locality of M. galeatum (in the Vatomandry district of Toamasina province).

It should be further noted that the P sheet of Service Forestier 13908, cited here as a paratype of M. pseudogaleatum , was previously determined by M. Jacques-Félix as M. pileatum . This material would also key to M. pileatum in JACQUES-FÉLIX (1985a) on account of having young branchlets terete (not compressed) and fruits 17–18 × 21–22 mm (not 14 × 11 mm as cited by him for M. galeatum ). However, terete branchlets can no longer be used as a diagnostic character for M. pileatum since this feature is shared with M. pseudogaleatum . In addition, the dimensions of the fruit are not a good character to distinguish between M. galeatum , M. pileatum and M. pseudogaleatum . For example, the collection Service Forestier 28157 (K, MO, P, TEF), which was cited by JACQUES-FÉLIX (1985a) under M. galeatum , has fruits of c. 23 × 23 mm. Additional confirmation that the mature fruits of M. galeatum are indeed much larger than was described by JACQUES-FÉLIX (1985a) is provided by several recent collections determined by me as belonging to this species (viz. Razanatsima 170, K, MO; Rakotoarivelo et al. 574, MO, NU; and Antilahimena 8125, MO). Even the character of the anther connectives, said by JACQUES-FÉLIX (1985a) to be conical in M. galeatum and subulate in M. pileatum , does not hold up to added scrutiny. On the other hand, the differing leaf dimensions of M. galeatum and M. pileatum are a seemingly useful character, i.e., leaves smaller 6–9(–12.5) × 3–4.5(–7.5) cm in the former vs. larger 12.5 –15.5 × 6.5–7.5 cm in the latter. The leaf dimensions of M. pseudogaleatum (as per the above description) fit well within the specified range of M. galeatum but are too small to be a good match for M. pileatum .

Paratypus. – MADAGASCAR. Reg. Atsimo-Atsinanana [Prov. Fianarantsoa]: Amporoforo , Farafangana , 26.VII.1955, fr., Service Forestier 13908 ( P, TEF) .

Figures

Fig. 8. – Memecylon pseudogaleatum R.D. Stone. A. Flowering branch; B. Leaf; C. Floral bud; D. Flower after anthesis; E. Petal; F. Stamen; G. Fruit. [Service Forestier 15244, TEF] [Drawing: S. Burrows]

Fig. 2. – Geographic distribution of Memecylon complanatum R.D. Stone (closed circle), M. convergens R.D. Stone (closed diamonds), M. fofifa R.D. Stone (open circles), M. longipetiolatum R.D. Stone (open square), M. paraxenum R.D. Stone (closed star), M. potamicum R.D. Stone (closed triangle), M. pseudogaleatum R.D. Stone (closed cross), M. subchartaceum R.D. Stone (open stars), and M. unguiculare R.D. Stone (closed square), mapped on the bioclimatic zones of Madagascar (after CORNET, 1974; see SCHATZ, 2000).