Memecylon majus R.D. Stone, 2022

Stone, Robert Douglas, 2022, Ten new species of Memecylon (Melastomataceae) from Madagascar, Candollea 77 (1), pp. 81-103 : 96-98

Memecylon majus R.D. Stone , sp. nov. ( Fig. 9 ).

H o l o t y p u s: MADAGASCAR. R e g . S AVA [Pr o v. Antsiranana]: Marojejy NP, just across stream from 2nd camp, 14°26'05"S 49°45'38"E, 750 m, 1.II.2008, fl., Stone et al. 2656 (CAS-1104887!; iso-: G [ G00379396 ]!, MO-6196939!, P [ P05206814 ]!, TAN!) .

Aff ine Memecyloni pedunculato Jacq.-Fél., sed ab eo laminis foliaribus majoribus plerumque 6– 9 × 2.3–3.5 cm (non 4.3 – 6.1 × 1.3 – 2.4 cm) elliptico-acuminatis (non ovato-acuminatis) basaliter cuneatis (non rotundatis) et floribus majoribus hypantho-calyce 2.5 × 3.5– 4 mm (non 2 × 3–3.5 mm), petalis 3 × 1.75 mm (non 2 × 1.25 mm) differt.

Shrubs or trees evergreen, 4– 8 m high; young branchlets terete to subquadrangular, bark dark brownish-black soon exfoliating in elongate-rectangular strips to reveal whitish inner bark; older branchlets with nodes thickened; internodes (1.7 –)2.5–5(–8) cm long. Leaves thinly coriaceous, petiolate, dark olive green on adaxial surface, drying brown abaxially (sometimes mottled with patches of lighter and darker brown); petioles 2–4 mm long; blades elliptic to narrowly elliptic, (3.4 –)6 – 9(– 11.6) × (1.4 –)2.3 – 3.5(– 4.5) cm, base cuneate, apex ± acuminate, acumen (3.5–)6.5– 14(– 20) mm long, obtuse; midnerve finely impressed on adaxial surface; transverse veins 6– 11 pairs faintly prominent on both surfaces in dried material, departing at an acute angle then nearly perpendicular to slightly oblique relative to midnerve, confluent with similarly weak intramarginal nerves; margins slightly revolute. Cymes up to 1.5(–2) cm long, solitary or in fascicles of 2–3 at nodes below leaves, 1– 2 times branched and (1 –)3– 5(– 7)-flowered; peduncles (0.5–)1 –5(–7.5) mm long, compressed; secondary axes (0.5–)2–4.5(–7) mm long, quadrangular; additional axes similar but shorter; bracts narrowly triangular, 1–1.5 mm long, acute, early deciduous; true pedicels short (flowers sessile or nearly so), rarely 1– 2 mm long. Flowers borne individually at ends of inflorescence axes; hypantho-calyx white suffused with violet near margin, obconic to campanulate, 2.5 × 3.5 –4 mm, margin with four V-shaped sinuses c. 0.5 mm deep, lobes rounded; corolla white in bud, narrowly conical-acute, 2.5 mm long; petals pale violet, ± triangular in outline, 3 × 1.75 mm, base ± auriculate above claw 0.5 mm long, apex acuminate-acute, margins scarious; staminal filaments white, 4.5–5 mm long; anthers pale yellow, c. 3 mm long, thecae positioned at anterior end, connective moderately incurved by dorsal oil-gland situated c. 0.5 mm behind thecae, posterior extremity narrowly conical-acute, extending 1.5 mm past gland; style white, c. 6 mm long. Fruits globose, 8–8.5 mm in diam., white when immature, turning red when ripe; calycinal crown appressed to summit of ovary.

Etymology. – The epithet majus is a neuter adjective meaning “greater”, in reference to the larger leaves and flowers of this species in comparison to the closely related and sympatric Memecylon pedunculatum Jacq. -Fél.

Distribution and ecology. – Northeastern Madagascar (SAVA region), known only from the Marojejy and Anjanaharibe massifs near the town of Andapa. Habitat in humid forests at elevations of 750–1000(–1580) m.

Conservation status. – Memecylon majus is known from four locations with an estimated EOO of 85 km ² and an AOO of 20 km ². All of the known locations are in protected areas including the Marojejy National Park (60,050 ha, first gazetted in 1952) and the Réserve Spéciale d’Anjanaharibe-Sud (26,903 ha, first gazetted in 1958), both of which are managed by Madagascar National Parks ( GOODMAN et al., 2021). Marojejy has

[A, B, E–H: Stone et al. 2656, CAS; C: Stone et al. 2657, CAS; D: Stone et al. 2662, CAS; I: Razafimandimbison et al. 232, CAS] [Drawing: S. Burrows]

seen a relatively minor loss of 846 ha (1.7 %) of moist evergreen forest between the years 1996 and 2016, and at Anjanaharibe Sud the deforestation rate has been similarly low, 404 ha (1.6 %) over the same time period ( GOODMAN et al., 2021). Ongoing anthropogenic pressures include exploitation of hardwoods, collection of non-woody forest products, uncontrolled fires (Marojejy), slash-and-burn agriculture (Anjanaharibe Sud), and small-scale mineral extraction (Anjanaharibe Sud) ( GOODMAN et al., 2021). Based on its limited AOO and the apparent threats, M. majus would meet the criterion B for listing as “Endangered” in accordance with the IUCN Red List Categories and Criteria ( IUCN, 2012), but it would be better assessed as “Near Threatened” [NT] contingent upon the continued effectiveness of habitat-specific conservation and management measures ( IUCN, 2019).

Notes. – Molecular analyses (R.D. Stone, unpubl. data) indicate that Memecylon majus is the sister-species of M. pedunculatum in Memecylon sect. Clavistamina (sensu JACQUES-FÉLIX, 1985 a). Also appearing in this species-group are M. myricoides Naudin and M. xiphophyllum R.D. Stone. However , Memecylon sect. Clavistamina as previously circumscribed is evidently not monophyletic, with the type species M. longipetalum H. Perrier and a different species-group including M. eduliforme Aug. DC. , M. clavistaminum Jacq. - Fél., M. laureolum Jacq. -Fél., and M. pterocladum R.D. Stone appearing elsewhere within the Malagasy clade sensu STONE (2014).

Based on its morphology, Memecylon majus belongs to a group of montane species defined by the character of young branchlets with brownish-black bark soon exfoliating in narrow, longitudinal strips to reveal whitish inner bark, as well as the character of flowers and fruits short-pedicellate to ± sessile above the peduncle ( STONE & CALLMANDER, 2011). Also belonging to this species-group are M. subsessile , M. pedunculatum , M. centrale (Jacq.-Fél.) R.D. Stone, and the newly described M. ourantherum R.D. Stone (see below). The flowers of M. centrale have not been seen, but the other species all have flowers with an anther-gland present, in contrast with the protologue of Memecylon sect. Clavistamina described as being “without gland” ( JACQUES-FÉLIX, 1985 a).

Memecylon majus and M. pedunculatum both occur in the Marojejy massif and might be confused with each other, but M. majus differs by its larger, elliptic-acuminate leaves with base cuneate (not ovate-acuminate with base rounded) and larger flowers. The leaves of M. majus are also quite similar to those of the common and widespread species M. louvelianum H. Perrier , leading to possible confusion. However, M. louvelianum has smaller flowers, and its fruits have a distinctive character, i.e. with the top of the ovary prominent and projecting above the persistent calycinal crown (vs. calycinal crown appressed to the summit of the ovary in M. majus ). Molecular analyses further indicate that the resemblance between M. majus and M. louvelianum is only superficial, i.e. the two species are not closest relatives (R.D. Stone, unpubl. data).

The following collections are clearly close to Memecylon majus but are from outside the type region and have generally smaller leaves, of about the same size as those of M. pedunculatum but elliptic in outline (not ovate) and with base cuneate (not rounded). They remain unplaced to species pending further study: Antilahimena 2330 (K, MO, NU), Antilahimena 2511 (K, MO, NU, P), Birkinshaw et al. 1773 (G, MO, NU), Service Forestier 35131 (TEF), Vasey & Velo 31 (CAS, MO, P, WAG) and 69 (K, MO, P).

Additional specimens examined. – MADAGASCAR. Reg. SAVA [Prov. Antsiranana]: R. N. I. Marojejy, on trail leading N into reserve from Tanambao , 14°32'S 49°42'E, 750 m, 15. V .1987, fr., Nicoll 654 ( K, MO, P, TAN); ibid. loco, aux env. du sommet d’Ambatosoratra, 14°32'S 49°42'E, 1583 m , VI .1994 , fr., Ravelonarivo et al. 219 (CAS, K); RS d’Anjanaharibe Sud, au S de campement à Mandritsarahely , 14°46'S 49°30'E, 985 m, 10.VII.1996, fr., Razafimandimbison et al. 232 ( BR, CAS, MO, P); Marojejy NP, along trail between 1 ST and 2nd camps, 14°26'05"S 49°45'38"E, 750 m, 1.II.2008, fl. & fr., Stone et al. 2657 ( CAS, G, MO, P, TAN), 2657 A (CAS, MO, P, TAN); ibid. loco, along trail between 2nd and 3 Rd camps, 14°26'08"S 49°45'26"E, 900 m, 2.II.2008, fl., Stone et al. 2662 ( CAS, K, MO, P, TAN); ibid. loco, Takhtajania trail, 14°45'15"S 49°29'10"E, 1006 m, 14.II.2006, fl., Tosh et al. 360 ( BR, CAS, MO, P, TAN) .

Figures

Fig. 9. – Memecylon majus R.D. Stone. A. Flowering branch; B. Section of branchlet showing exfoliating character of bark; C, D. Leaves; E. Inflorescence with floral buds; F. Flower at anthesis; G. Petal; H. Stamen; I. Fruit.