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

description: 3. Melanoxerus maritimus Kainul., sp. nov. (Fig. 4).
H o l o t y p u s: MADAGASCAR. R e g. M e l a k y [Pro v. Mahajanga]: Distr. Maintirano, Lac Mandrozo, 17°32'43"S 44°02'26"E, 18 m, 23.XI.2015, fl. & fr., Gautier, Luino & Rasolonjatovo LG 6196 (G [G00419027]!; iso-: MO!, P!, S!, TEF).
Melanoxerus maritimus Kainul. differs from M. suavissimus (Homolle ex Cavaco) Kainul. & B. Bremer in its rounder leaves (leaf length/width ratio 4:3–1:1 vs. 3:1–3:2), that have a truncate to cordate leaf base (vs. cuneate to attenuate), and corolla lobes that are rounded to indented (vs acute).
Shrubs or trees up to 10 m tall and 28 cm dbh, with mostly sympodial branching. Bark pale grey to pale brown, smooth, flaky. Stipules 3.5 –4.7 × 3.6– 4.5 mm, broadly triangular, interpetiolar, caducous. Leaves semi-deciduous, petioles 2.8– 5.2 cm long, adaxially canaliculate; leaf blades papyraceous to subcoriaceous, cordiform to broadly ovate, 7.5–12.7 × 5–10.5 cm; bases cordate to truncate; apices acute; adaxial surface dark green when fresh, drying dark brown to black, smooth and very glossy, glabrous except for the lower part of the midrib (trichomes 0.1–0.5 mm long); 6–9 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 green when fresh, drying dark brown to blackish, glossy, glabrous, but with tuft domatia often present in the vein axils. Flowers solitary, terminal, very fragrant; pedicels up to 14 mm long; hypanthium narrowly urceolate, 5–18 × 3–4 mm, glabrous; calyces green; calyx tubes 1–4.5 mm long, externally and internally glabrous; calyx lobes 3.4–6.2 × 1.2–2 mm, narrowly triangular and recurved; corollas fleshy, funnelform, straight; corolla tubes 2–3.7 cm long, externally pale yellow with a greenish base, glabrous, internally white with red spots and lines, finely pubescent (trichomes c. 0.5 mm long). Corollas lobes white, 2–2.7 × 1.6–3 cm, ovate to orbicular, rounded to truncate or indented, spreading horizontally at anthesis; stamens subsessile (filaments 2–4 mm long), attached c. 10 mm below corolla sinus and c. 4 mm from anther base; anthers c. 15 × 2 mm, linear, exserted for 1–3 mm. Styles simple, clavate, with shallow longitudinal grooves, 30–35 mm long, glabrous, exserted for 5–9.5 mm; stigma shortly bifid (lobes c. 3 mm long). Fruits ellipsoid, 2.5 –5.1 × 1.6– 3.7 cm, smooth, glabrous, (colour of mature fruit unknown) with numerous beige lenticels (0.1–1 mm in diam.), fleshy-indehiscent; calyx tube persistent but lobes caducous. Seeds not seen.
Etymology. – This species grows near the sea and that is what the specific epithet maritimus refers to.
Vernacular names. – “Ndraniana” (Service Forestier 10585); “Tselitselika” (Bertrand 16).
Distribution, habitat and ecology. – Melanoxerus maritimus is known from sea level to 30 m in elevation in coastal areas of the Boeny, Melaky, and Sofia Regions (Mahajanga Province) (Fig. 1). It grows in low canopy, dry deciduous forests on dunes and on edges of salt flats or mangroves.
Phenology. – Flowering material has been collected from June to November, and fruiting material from July to February.
Conservation status. – Melanoxerus maritimus is known from less than ten locations, (three of which are within the recently protected areas of Antrema, Bombetoka Belemboka, and Mandrozo), with an estimated area of occupancy (AOO) of less than 2000 km ². It appears restricted to littoral dry forest. This habitat is impacted for firewood or charcoal production (also noted on label of De Block & Rakotonasolo 806). It is projected that the number of locations and the number of mature individuals continue to decline, and this species can therefore be assigned a preliminary conservation status of “Vulnerable” [VUB2ab(iii)] according to IUCN Red list Categories and Criteria (IUCN, 2012). However, more information is needed about the population size of this species.
Notes. – Melanoxerus maritimus has solitary flowers with a funnelform corolla and pubescent corolla throat, and in these characters it most resembles M. suavissimus, but it is recognized by its ± cordiform leaves that are almost as wide as long (leaf length/width ratio 4:3–1:1 vs. 3:1–3: 2 in M. suavissimus), and by having corolla lobes that are rounded to indented rather than acute. The leaves of M. maritimus are glossy below and very glossy above. They remain glossy when dried and almost appear varnished. It is notable that none of the specimens examined in this study is lacking leaves, and that specimens collected during the dry season still retain some leaves. This species is therefore probably best considered semi-deciduous as opposed to deciduous.
Selected additional material examined. – MADAGASCAR. Reg. Boeny [Prov. Mahajanga]: [Distr. Mahajanga I] Antananamasadza [probably Antanimasaja, now part of Mahajanga town], 1912, Afzelius 266 (P, S); Katsepy, c. 10 m, 19.II.1950, ster., Bertrand 16 (P); Distr. Mahajanga II, Antsanitia, Belamonty forest, 15°34'19"S 46°25'04"E, 9 m, 14.II.1999, fr., De Block & Rakotonasolo 806 (BR, MO, TAN); Katsepy, 15°45'56"S 46°14'21"E, 0 m, 22.VII.1995, fl. & fr., Edmondson et al. 95–17 (MO, P); ibid. loco, 8.IX.1912, fl., Kaudern s.n. (S); ibid. loco, 15°42'35"S 46°12'03"E, 10.XI.2005, fl., Labat et al. 3534 (K, P); ibid. loco, 10.XI.2005, fr., Labat et al. 3535 (G, K, MO, P); Antsanitia, 15°34'31"S 46°25'7"E, 30 m, 7.I.2000, fr., Rakotonasolo RNF 132 (K, TAN); Forest station E of Antsanitia village, 15°34'31"S 46°24'26"E, 16 m, 15.II.2013, fr., Ralimanana et al. 1803 (BR, K, MO, P, TAN); Distr. Mahajanga II, Ampasimariny, 9 m, 23.VIII.1954, fl. & fr., Service Forestier 10585 (MO, P, TEF). Reg. Melaky [Prov. Mahajanga]: Region de Tambohorano, 23.VI.1930, fl., Decary 8083 (P); Ambongo, 1841, fr., Pervillé 673 (K, P). Reg. Sofia [Prov. Mahajanga]: SW of Antangena, 15°28'S 47°09'E, 0 m, 25.X.1987, fl. & fr., Bisset M12 (K); Distr. Analalava, Antonibe, 15°01'44"S 47°13'17"E, 19.VIII.2007, fl. & fr., Randriatsivery 207 (MO, 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 112-114, DOI: 10.15553/c2021v761a11, http://zenodo.org/record/5683793