Memecylon fissuricola R.D. Stone, 2022

Stone, Robert Douglas, 2022, Ten new species of Memecylon (Melastomataceae) from Madagascar, Candollea 77 (1), pp. 81-103 : 88-90

Memecylon fissuricola R.D. Stone , sp. nov. ( Fig. 4 , 5 ).

Holotypus: MADAGASCAR. Reg. DIANA [Prov. Antsiranana]: RS Ankarana, piste vers le lac vert, 12°54'S 49°06'E, 180 m, 19.II.1994, fl., Andrianarisata et al. 30 ( P [ P00516014 ]!; iso-: CAS-942152!, G [ G00379393 ] image!, MO!) .

Simile Memecyloni boinensi H. Perrier, sed ab eo laminis foliaribus basiliter angustatis (non rotundatis) in petiolum decurrentibus, petalis pallide violaceis (non albis) et fructibus plus minusve ellipsoideis (non globosis) differt.

Shrubs or small trees evergreen, 1–4 m high with bark light reddish-brown, finely longitudinally fissured; branchlets with bark smooth, whitish gray; young branchlets compressed and dorso-ventrally 2-grooved, soon becoming terete with age; nodes ± thickened; internodes (0.5–)1.3 –2.8(– 6) cm long. Leaves subcoriaceous, petiolate, bright green and somewhat glossy adaxially, paler and dull abaxially; petioles 1–2 mm long; blades elliptic to obovate, (1.7–)2.5–3.5(–4.4) × (0.8–)1.3–1.9 (–2.2) cm, base ± narrowed and confluent with petiole, apex rounded to retuse or vaguely obtuse-acuminate; midnerve finely impressed adaxially, conspicuous and ± prominent abaxially; intramarginal nerves and transverse veins invisible or nearly so in dried material, the latter oriented at an oblique angle relative to midnerve. Cymes up to c. 1.5(–2) cm long, (1 –)3(– 4)-flowered, solitary or geminate in leaf axils and terminally on branchlets, sometimes also on recently defoliated nodes; peduncles compressed, (1–)3–7(–10.5) mm long; secondary axes (1–)2–4(–5) mm long; bracts narrowly triangular-acute, c. 1 mm long, early deciduous. Flowers borne individually at ends of inflorescence axes, on short pedicels 0.3 – 0.7(– 1) mm long; hypantho-calyx yellow, obconic to cupulo-patellate, 2.5 × 3 mm, margin shallowly sinuatedentate, lobes broadly rounded, scarious margined; corolla in bud conical-apiculate, c. 2 mm long; petals pale violet, broadly ovate-triangular to suborbicular, 3 × 2–3 mm, base truncate above claw c. 0.5 × 0.5 mm, apex acute to apiculate; staminal filaments pale violet, c. 5 mm long; anthers pale yellow, 1.3 mm long, thecae fronto-ventral, dorsal oil-gland narrowly elliptic, posterior extremity of connective obtuse to subacute; style white, 8 mm long. Fruits yellowish (immature?), subglobose to ± ellipsoid, 9– 12 × 9–10 mm; persistent calycinal crown 1 mm high.

Etymology. – The epithet fissuricola is a compound derived from the Latin noun fissura meaning “crevice” and the agent noun -cola meaning “inhabitor”. It functions as an adjective and means “crevice-dweller”, in reference to the habitat in shallow soil and crevices of calcareous rock.

Distribution and ecology. – Northern Madagascar (Diana region), evidently restricted to the Ankarana massif. Habitat in dry, semi-deciduous forests on the rocky, calcareous plateau, at elevations of 80– 200 m.

Conservation status. – Memecylon fissuricola is known from approximately five locations with an estimated EOO of 25 km ² and an AOO of 20 km ². Its entire population evidently resides within the 18,225 ha Réserve Spéciale d’Ankarana gazetted in 1956 and managed by Madagascar National Parks ( GOODMAN et al., 2021). Within the protected area there has been no measurable loss in hectarage of dry deciduous forest between the years 1996 and 2016, yet there are ongoing anthropogenic pressures including exploitation of wood products and wildfires which have increased in frequency since 2015 ( GOODMAN et al., 2021). Based on its limited AOO and the

[A, C: Leeuwenberg et al. 14348, P; B: Stone et al. 2642, CAS; D–F: Andrianarisata et al. 30, P; G: Service Forestier 10503, P] [Drawing: S. Burrows] B. Crown of tree showing habit of tortuous branching; C. Flowering branchlet; D. Branchlet with young, developing fruits.

[A, D: Stone et al. 2639; B, C: Stone et al. 2642] [Photos: A, C, D: C. Christian; B: R.D. Stone]

apparent threats, M. fissuricola would meet the criteria for listing as “Endangered” [EN B2ab(iii)] in accordance with the IUCN Red List Categories and Criteria ( IUCN, 2012), but it would also seem to qualify for “Near Threatened” [NT] status dependent upon the continued effectiveness of habitat-specific conservation and management measures ( IUCN, 2019).

Notes. – Memecylon fissuricola has been confused with M. boinense H. Perrier , but molecular analyses indicate the resemblance is only superficial, i.e. the two species are not closest relatives (R.D. Stone, unpubl. data). The new species further differs from M. boinense in having leaf-blades basally angustate and decurrent to the petiole (vs. rounded), petals pale violet (vs. white), and fruits ± ellipsoid (vs. globose). The two species are also wholly allopatric, with M. boinense occurring further south and with its nearest known locality separated from M. fissuricola by a distance of c. 290 km.

Additional specimens examined. – MADAGASCAR. Reg. DIANA [Prov. Antsiranana]: Massif de l’Ankarana , 5.XI.1990, ster., Bardot Vaucoulon 237 ( P); ibid. loco , 7.XI.1990, ster., Bardot Vaucoulon 257 ( P); ibid. loco , 17.XI.1990, fr., Bardot Vaucoulon 300 ( P); ibid. loco , 19.I .1991 , fl., Bardot Vaucoulon 402 (P); ibid. loco, road towards Lac Vert , 12°50'47"S 49°06'18"E, 82 m, 26.V .1999 , fr., De Block et al. 1025 (BR, MO); ibid. loco, near Campement des Anglais , 12°54'S 49°08'E, 150 m, 29.I .1994 , fl., Leeuwenberg et al. 14348 (CAS, K, MO, P, WAG); Ambilobe, Ankara SO, 27.VII.1954, fr., Service Forestier 10503 ( P); ibid. loco, on plateau directly above Grotte des Chauve Souris , 12°57'20"S 49°06'59"E, 200 m , 15.II.2007, fl. & imm. fr., Stone et al. 2639 ( CAS, MO, P, TAN); ibid. loco, Tourelles de Tsingy , 12°56'54"S 49°07'37"E , 17.II.2007, fl., Stone 2642 ( CAS, MO, P, TAN) .

Figures

Fig. 4. – Memecylon fissuricola R.D. Stone. A. Flowering branch; B. Leaves; C. Floral bud; D. Open flower; E. Petal; F. Stamen; G. Fruit.

Fig. 5. – Memecylon fissuricola R.D. Stone. A. Trunk and lower branches growing from a crevice of calcareous rock;