Melanoxerus atropurpureus Kainul. 2021, sp. nov.
Creators: name: Kainulainen, Kent
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Gentianales
Rubiaceae
Melanoxerus
Melanoxerus atropurpureus

description: 2. Melanoxerus atropurpureus Kainul., sp. nov. (Fig. 3).
– Euclinia sp. 2 in KAINULAINEN & BREMER (2014: 820).
H o l o t y p u s: MADAGASCAR. R e g. M e l a k y [Pro v. Mahajanga]: Distr. Maintirano, Beanka, partie S, Sarodrano, 18°03'27"S 44°30'50"E, 359 m, 26.XI.2011, fl., Gautier, Tahinarivony & Bolliger LG 5744 (G [G00340493]!; iso-: BR!, K [K000918390]!, MO!, P!, TEF).
Melanoxerus atropurpureus Kainul. is similar to M. antsirananensis Kainul. in its pauciflorous inflorescences and flowers with campanulate corollas, but it differs in having larger leaves (10–30 × 6.5–14.5 cm vs. 7–18 × 4.5–8.5 cm) that are broadly lanceolate (vs. obovate), and by the uniformly purple corolla throat (vs. whitish corolla throat with red, purple or violet and sometimes also green spots).
Shrubs or trees up to 26 m tall and 25 cm dbh. Bark grey and smooth, flaky. Stipules 2.5 – 13 × 3– 5 mm, triangular, interpetiolar, caducous. Leaves deciduous, petioles 2–7.5 cm long, adaxially canaliculate; leaf blades papyraceous, broadly lanceolate, 10–30 × 6.5–14.5 cm; bases cuneate to rounded, sometimes oblique; apices acute to acuminate; adaxial surface dark green when fresh, drying dark brown to black, smooth and glossy, sparsely pubescent along venation; 8 –12 pairs of conspicuous, ± pinnate secondary veins, tertiary venation reticulate; midrib prominent, pale green when fresh, ± the same colour as the leaf when dry; abaxial surface pale green when fresh, drying dark brown to blackish, glabrous except the pubescent veins (trichomes c. 0.1 mm); tuft domatia often present in the vein axils. Flowers solitary or few (<10), sessile, congested and umbel-like inflorescence; pedicels up to 15 mm long; hypanthium narrowly urceolate, 8–15 × 5–8 mm, glabrous. Calyces green; calyx tubes 2–3.5 mm long, externally and internally glabrous; calyx lobes 3–6.5 × 0.5–3.5 mm, narrowly triangular and recurved; corollas fleshy, campanulate to broadly urceolate; corolla tubes 1.8–4.8 cm long, externally white with purple and pale green streaks, glabrous, internally dark purple to violet, glabrous or with a sparse indument (trichomes 0.4–1 mm) in the lowermost (c. 0.5 cm) part of the tube. Corollas lobes white, 1.5–3 × 1.2–2.5 cm, ovate, rounded to acute, spreading horizontally at anthesis; stamens subsessile (filaments 1–4 mm long), attached 25–35 mm below corolla sinus and 4–7 mm from anther base; anthers 22–27 × 2–3 mm, linear, included (tips 5– 6 mm below corolla sinus). Styles simple, clavate, with shallow longitudinal grooves, 28–33 mm long, glabrous, included; stigma shortly bifid (lobes 1–1.5 mm long). Fruits (globose) ellipsoid, 3.5– 7 × 3– 6 cm, smooth, glabrous, olive to brown or maroon with numerous beige to pale grey lenticels (1–2 mm in diam.), fleshy-indehiscent with yellowish to white pulp; calyx tube sometimes persistent, but lobes caducous. Seeds flattened, irregularly angled, 8–13 mm in diam., c. 2 mm thick, smooth, ± translucent, pale yellow when fresh, drying black.
Etymology. – The specific epithet atropurpureus refers to the dark purple colour of the interior of the corolla tube in this species.
Vernacular names. – “Andrivitsy” (Réserves Naturelles 7791); “Hazondanitra” (Service Forestier 4953); “Voafotaka” (Labat & Deroin 2280); “Voangorindambo” (Service Forestier 29775).
Distribution, habitat and ecology. – Melanoxerus atropurpureus occurs in the Boeny, Melaky, and Sofia Regions (Mahajanga Province) and in the southernmost part of the DIANA Region (Antsiranana Province) (Fig. 1), where it grows in dry to humid, deciduous or evergreen forests from sea level to 450 m in elevation.
Phenology. – Flowering material has been collected from October to November and fruiting material from December to July.
Conservation status. – Melanoxerus atropurpureus has a wide distribution in western Madagascar and is known from several protected areas including Ankarafantsika, Bemaraha, and Namoroka. It can therefore be assigned a preliminary conservation status of “Least Concern” [LC] according the IUCN Red list Categories and Criteria (IUCN, 2012). However, it is not a commonly collected species, and more information is needed about its population size.
Notes. – The specimen Perrier de la Bâthie 1155A from the Ankara plateau is in poor shape but probably belongs to this species. In this species the exocarp of the fruit is often almost completely hidden by lenticels (Fig. 3F).
Melanoxerus atropurpureus is the tallest growing species in the genus. It mostly resembles M. antsirananensis but has larger leaves (10–30 × 6.5–14.5 cm vs. 7–18 × 4.5–8.5 cm) that are broadly lanceolate rather than obovate. Furthermore, the corolla throat is uniformly dark purple (white with red to violet spots in M. antsirananensis).
Selected additional material examined. – MADAGASCAR. Reg. Boeny [Prov. Mahajanga]: Distr. Marovoay, Ankarafantsika NP, Ampijoroa forest station, 16°18'52"S 46°49'04"E, 190 m, 24.I.2000, fr., Davis et al. 2500 (K, TAN); ibid. loco, 16°20'S 46°51'E, 200 m, 14.IV.1984, Dorr 3048 (BR, K, P, MO); ibid. loco, 16°19'S 46°49'E, 70–100 m, 7.IV.1988, Gentry & Schatz 62050 (MO); Plateau d’Ankara, X.1900, fl., Perrier de la Bâthie 1155 A (P); Manongarivo (Ambongo), XI.1903, fl., Perrier de la Bâthie 1640 (P); ibid. loco, X.1905, fl., Perrier de la Bâthie 4103 (P); ibid. loco, I.1904, fr., Perrier de la Bâthie 6944 (P); Ankarafantsika, 16°20'05"S 46°47'06"E, 3–9.II.1997, fr., Rabevohitra 3027 (TEF); ibid. loco, 16°18'S 46°49'E, 22.IV.1994, fr., Rajemisa 19 (MO, P, TAN); Distr. Mahajanga II, Mariarano, Ankatsabe forest, 15°28'30"S 46°41'24"E, 16 m, 20.IV.2007, fr., Rakotoarivelo 94 (MO, P, TAN); Soalala, 15.VII.1977, fr., Rakotozafy 1849 (TAN); Distr. Soalala, Andranomavo, Vilanandro, Tsingy Namoroka, Ambatomay forest, 16°28'36"S 45°20'52"E, 153 m, 9.IX.2012, fr., Ravelonarivo et al. 4523 (MO, TAN); Andranomavo, 19.XI.1955, fl., Réserves Naturelles 7791 (P, TEF); Ankarafantsika, s.d., fr., Service Forestier 19 (P); Tsingy Namoroka, 4.IV.1933, fr., Service Forestier 36 (P); sine loco, 4.IV.1933, fr., Service Forestier 54 (BR, K, P); Ankarafantsika, Ampijoroa, 15.V.1952, fr., Service Forestier 4953 (P, TEF); ibid. loco, 16.VI.1954, fr., Service Forestier 10204 (P); Ambato-Boeny, Andranovato, Ankijabe, 20.I.1959, fr., Service Forestier 19261 (TEF); Ambongo, Soalala (baie de Baly), 22.XI.1965, fl., Service Forestier 24244 (BR, P, TEF); by lake Ampijoroa, 28.II.1980, fr., Service Forestier 29775 (TEF). Reg. DIANA [Prov. Antsiranana]: Distr. Ambanja, Ampasindava, Andranomatavy forest, 13°40'04"S 47°59'21"E, 295 m, 25.XI.2009, fl., fr., Madiomanana et al. MAD 266 (G, K, MO, P, TEF); along Andranomatavy river, 13°40'39.19"S 47°58'30.24"E, 260 m, 2.VII.2012, fr., Tahinarivony & Rasoanaivo TAJ 699 (G). Reg. Melaky [Prov. Mahajanga]: Beanka, Ambinda-Nord, 17°55'51"S 44°28'39"E, 216 m, 5.II.2012, fr., Hanitrarivo et al. HRM 146 (G, S); Ambodiria, 1 km E of Ambinda (RN 9, near Antsalova), 18°38'S 44°42'E, 100–200 m, 3.XII.1992, fr., Labat & Deroin 2280 (K, P, TAN); Beanka, Sarodrano, 18°02'55"S 44°31'13"E, 446 m, 11.XII.2011, fl., Nusbaumer et al. LN 3073 (G, K); Antsalova, 20.III.1993, fr., Villiers et al. 4851 (MO, P); Belitsaka, Ankilimanarivo, Beanka forest, 18°03'37"S 44°31' 37"E, 319 m, 16.IV.2011, fr., Razakamalala & Germain 6382 (MO, S). Reg. Sofia [Prov. Mahajanga]: entre Antsohihy et Befandriana-Nord, X.1962, fl., Bosser 16697 (P, TAN); Distr. Antsohihy, Anjimangirana, Analananbe, Andrafiborizina, 15°09'19"S 47°44'22"E, 200 m, 30.V.2000, fr., Rakotonasolo RNF 177 (BR, K, P, TAN).
description: Published as part of Kainulainen, Kent, 2021, A taxonomic revision of Melanoxerus (Rubiaceae), with descriptions of three new species of trees from Madagascar, pp. 105-116 in Candollea 76 (1) on pages 110-112, DOI: 10.15553/c2021v761a11, http://zenodo.org/record/5683793