Memecylon conjugens R.D. Stone, 2022

Stone, Robert Douglas, 2022, Ten new species of Memecylon (Melastomataceae) from Madagascar, Candollea 77 (1), pp. 81-103 : 84-86

Memecylon conjugens R.D. Stone , sp. nov. ( Fig. 2 ).

H o l o t y p u s: MADAGASCAR. R e g. S AVA [Pr o v. Antsiranana]: N of Andapa, RNI Marojejy , 14°28'57"S 49°38'12"E, 1100– 1600 m , I.1994, fl. buds, Malcomber et al. 2687 (CAS-926817!; iso-: K!, MO-6262414!, NU!, P [ P00516010 ]!) .

Ob folia caudato-acuminata Memecyloni longicuspi Baker et M. peracuminato H. Perrier simile, sed a primo ramulis teretibus (non quadrangularibus et anguste alatis), hypanthocalyce majore 3 × 3.5– 4 mm (non 1.5 × 2.5 mm), calycis margine sinuato-dentato (non truncato 4-denticulatoque), fructus corona calycina circa 1 mm longa (non subprominente); a secundo petiolis brevioribus 2 – 3 mm (non 3 – 5 mm) longis, cymularum bracteis deciduis (non persistentibus), floribus pedicellatis (non subsessilibus) pedicellis plerumque 2–3.5 mm longis et corolla in alabastro conico-apiculata (non conico-obtusa); ab ambobus cymulis longioribus 2(– 3) cm, pedunculis 6 – 11 mm longis et fructibus multo majoribus 13–19 × 11–15 mm ellipsoideis vel late ovoideis differt.

Shrubs or small trees 4 – 8 m high, evergreen; ultimate branchlets slender, the youngest compressed, soon becoming terete with age; nodes ± thickened; internodes (1.4 –)2 – 4(– 5.3) cm long. Leaves subcoriaceous, petiolate, dark green and somewhat glossy above, paler and dull below, minutely roughened when dry; petioles 2–3 mm long; blades elliptic to narrowly elliptic or elliptic-ovate, (3–)4 –5.5(– 7) × (1.1–)1.8–2.4(–2.7) cm, base cuneate, apex caudate-acuminate, acumen (4 –)7 – 12(– 18) mm long, obtuse; midnerve finely canaliculate adaxially, conspicuous abaxially but not prominent or very slightly so towards the base of the blade; intramarginal nerves and transverse veins invisible. Cymes to c. 2(–3) cm long, 3–5(–6)-flowered, solitary or geminate in the leaf axils, sometimes terminally on the branchlets, and frequently also at the recently defoliated nodes; peduncles slender, compressed, (4 –)6 – 11(– 14) mm long; axis often extended by a slender internode (1 –) 3– 6 mm long; bracts rapidly deciduous, not seen. Flowers white (at least in bud), on slender pedicels (1.5 –)2–3.5(–4.5) mm long; hypanthocalyx obconic to campanulate, c. 3 × 3.5 – 4 mm, margin shallowly sinuate-dentate, lobes broadly rounded, scarious margined; corolla in bud conical-apiculate, c. 2 mm long; open flowers not seen; anthers in bud c. 2 mm long, thecae fronto-ventral, dorsal oil-gland narrowly elliptic, 0.7 mm long, posterior extremity of connective acute. Fruits purplish at maturity, broadly ovoid to ellipsoid, 13– 19 × 11– 15 mm; persistent calycinal crown c. 1 mm high, margin truncate.

Etymology. – The epithet conjugens is an adjective meaning “joined together”, in reference to the fact that the flowering material from Marojejy and fruiting material from Anjanaharibe-Sud were at first considered to be separate species.

Distribution and ecology. – Northeastern Madagascar (SAVA region), known only from the Marojejy and Anjanaharibe massifs near the town of Andapa. Habitat in montane, humid forests at elevations of 1100–1350 m.

Conservation status. – Memecylon conjugens is known from three locations with an estimated EOO of 50 km ² and an AOO of 12 km ². All of the known locations are in protected areas including the Marojejy National Park (60,050 ha) and

[A, B, E–H: Malcomber et al. 2687, CAS,NU,P; C, D, I, J: Ravelonarivo et al. 319, MO,P; K: Ravelonarivo & Rabesonina 486, NU] [Drawing: S. Burrows]

the Réserve Spéciale d’Anjanaharibe-Sud (26,903 ha), both of which are managed by Madagascar National Parks ( GOODMAN et al., 2021). Marojejy has 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. conjugens 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. – The presence of an anther-gland and the shallowly sinuate-dentate calyx margin of Memecylon conjugens indicate that it would be placed in Memecylon sect. Memecylon sensu JACQUES-FÉLIX (1985 a, 1985b). However, the limits of this section are in need of revision since molecular results suggest the group is not monophyletic ( STONE, 2014, unpubl. data; AMARASINGHE et al., 2021), and the type species ( M. capitellatum L.) is from Sri Lanka.

The leaves of the new species resemble those of Memecylon longicuspe Baker and M. peracuminatum H. Perrier in appearing 1-nerved with apex caudate-acuminate and acumen narrowly obtuse at the summit. However, this may not be an indication of its true affinity, and both M. longicuspe and M. peracuminatum are from east-central and southeastern Madagascar, while M. conjugens has a different and limited distribution in the northeast.

The fruits of Memecylon conjugens are variable, an unusual feature since other species of Malagasy Memecylon have a more-or-less consistent (often diagnostic) fruit size and shape. Among the additional specimens (paratypes) cited below, the fruits of Ravelonarivo et al. 319 are broadly ovoid (conspicuously wider below the middle), as are those of the NU and P sheets of Ravelonarivo & Rabesonina 486. However, the fruits of the CAS and MO sheets of Ravelonarivo & Rabesonina 486 are differently shaped, i.e. broadly ellipsoid or even obovoid (widest above the middle). The ovoid fruits of M. conjugens are similar to those of M. pedunculatum Jacq. -Fél., except that they are larger (11–15 vs. 8 mm in diam.), and the calycinal crown is prominent (vs. appressed to the summit of the ovary). Both of these species occur in the same region of northeastern Madagascar but are not closely related since M. pedunculatum lacks an anther-gland and has been placed in Memecylon sect. Clavistamina Jacq. -Fél. sensu JACQUES-FÉLIX (1985 a).

Additional specimens examined. – MADAGASCAR. Reg. SAVA [Prov. Antsiranana]: RS d’Anjanaharibe-Sud, env. du sommet, 14°40'55"S 49°28'20"E, 1336 m, 8.VII.1994, fr., Ravelonarivo et al. 319 ( CAS, G, MO, NU, P, TAN); ibid. loco, Camp no 2, 14°44'42"S 49°27'42"E, 1185–1335 m, 3.XI.1994, fr., Ravelonarivo & Rabesonina 486 ( CAS, G, MO, NU, P, TAN) .

Figures

Fig. 2. – Memecylon conjugens R.D. Stone. A. Flowering branch; B–D. Leaves; E. Inflorescence; F. Floral bud; G. Petal; H. Stamen; I–K. Fruit.