Sabicea ndjoleensis Zemagho, O. Lachenaud & Sonké, 2017

Zemagho, Lise A., Liede-Schumann, Sigrid, Lachenaud, Olivier, Dessein, Steven & Sonke, Bonaventure, 2017, Taxonomic revision of Sabicea subgenus Anisophyllae (Ixoroideae, Rubiaceae) from Tropical Africa, with four new species, Phytotaxa 293 (1), pp. 448-450 : 448-450

11. Sabicea ndjoleensis Zemagho, O. Lachenaud & Sonké , sp. nov. ( Fig. 25 )

Type :— GABON. Moyen Ogooué, ca. 10 km NNW of Ndjolé, on BSO forestry road, 276 m, 0°05’16.2’’S 10°44’43.5’’E, 26 February 2008, S. Dessein, O. Lachenaud, S. Janssens, Y. Issembe & T. Nzabi 2149 (holotype BR!; isotypes LBV!, MO!, P!, WAG!) .

Sabicea ndjoleensis resembles S. aurifodinae , S. crystallina and S. sciaphilantha in the sarmentose habit, leaves in very unequal pairs, stipules entire, corolla tube long, and inflorescences borne mostly on older stems. It differs from all these species in the outer bracts 6–9 x 5–6 mm (vs. 1.5–6.5 x 0.5–3 mm), completely enclosing the flowers in the bud stage (vs. hidden between the flowers). It is further separated from S. aurifodinae and S. crystallina by the densely pubescent stems (vs. glabrous or nearly so), and the dark purple (vs. white) calyx lobes, and from S. sciaphilantha by the stipules with free part 5–8 mm long (vs. 10–24 mm long), the calyx tube 1.5–4 mm long (vs. 0.7–1.2 mm long) and the calyx lobes densely felted outside, glabrous or appressed-pubescent inside (vs. glabrous outside and stiffly villose inside).

Scrambling, lianescent shrub; stems up to 1.5 m long (usually shorter), 2–5 mm thick, ± trailing and rooting at base, densely felted with buff woolly hairs intermingled with longer stiff hairs ca. 2 mm long when young, becoming ± glabrescent with age. Leaves opposite, strongly unequal with one of them much smaller; smaller leaves with petioles 0.1–0.2 cm long and blades 0.4–0.8 x 0.2–0.6 cm; normal-sized leaves with petioles 0.8–3.5 mm long, with same indumentum as the stems; blades elliptic to slightly obovate, (8–)10–24.5 x (3) 3.8–10 cm, strongly asymmetrical at base with proximal side rounded to subcordate and distal side truncate to obtuse inserted 1–6 mm higher, acuminate at apex, slightly coriaceous to papery, strongly discolorous; upper side dark green, sparsely villose above, with stiff hairs 0.7–2.5 mm long, intermingled with shorter woolly hairs on the midrib; lower side buff or greyish, densely felted with woolly hairs below; secondary veins 11–21 on each side of midrib. Stipules opposite, interpetiolar and connate at base with the petioles into a sheath 4–7 mm long, the free part narrowly triangular, entire, 5–8 x 1.5–3 mm, +/- erect, glabrous outside or with very sparse woolly hairs near the base, sometimes sparsely ciliate on the margin, glabrous inside except the base with silky hairs ca. 1.5 mm long. Inflorescences on older stems below the leafy nodes or more rarely in the axils of the lower leaves, 1–2 per node, sessile, densely glomerulate, 1.7–3 cm in diameter, many-flowered. Bracts and bracteoles numerous and not clearly distinct from each other, dark purple, spathaceous and completely enclosing the flowers when young, concave at base, +/- bifid or more rarely entire and acute at apex, the outer ones larger, 6–9 x 5–6 mm, the innermost ca. 4 x 1.2 mm, sparsely felted outside (at length becoming glabrescent), densely villose all over inside with silky hairs ca. 2 mm long. Flower buds with apex slightly enlarged and ovoid. Flowers 5-merous, sessile. Hypanthium densely villose with appressed silky hairs ca. 1.5 mm long. Calyx dark purple; tube 1.5–4 mm long, densely felted outside and sometimes villose with appressed silky hairs, glabrous or villose in upper half inside; lobes linear to narrowly triangular, 3–6 x 0.3–0.7 mm, acute at apex, rather thick and ± concave on the inner side, erect with the apex often

TAXONOMIC REVISION OF SABICEA SUBGENUS ANISOPHYLLAE

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+/- bending outwards, densely felted outside, glabrous to densely villose with appressed silky hairs ca. 1 mm long inside; one minute colleter between every pair of lobes. Corolla white; tube narrow, almost cylindrical, 8.5–11 x 1.5–2 mm; lobes triangular, 2.3–4 x 1.2–1.8 mm; lobes and distal half of tube densely villose outside, with long appressed silky hairs, the lower half of tube glabrous; mouth and base of lobes densely bearded with white moniliform hairs ca. 1 mm long inside; tube with 5 patches of hairs slightly above mid-height inside, the upper part either villose from the mouth down to the base of the anthers in long-styled flowers, or glabrous in short-styled flowers. Stamens either included, subsessile and attached around the upper 1/4 th of the tube in long-styled flowers, or half-exserted, subsessile and attached just below mouth in short-styled flowers; anthers ca. 2 x 0.3 mm long. Disk cylindrical, ca. 0.2 mm long, glabrous. Style glabrous, 11–12 mm long, exserted in long-styled flowers, ca. 5 mm long, included in short-styled flowers; stigmatic lobes narrowly elliptic, 1.2–1.7 mm long. Fruits green to purple, only known in the very young stage.

Etymology:— The species name derives from the town of Ndjolé ( Gabon) in the vicinity of which the species occurs.

Distribution: —Lower Guinea Domain. Endemic to the hills north of Ndjolé in central Gabon ( Fig. 26 ), where locally not rare. This area is home to several other endemic species, such as Combretum ndjoleense Jongkind (1993: 203) ( Combretaceae ), Dactyladenia ndjoleensis Breteler (1999: 111) and Magnistipula devriesii Breteler (1995: 193) ( Chrysobalanaceae ) and Tarenna ogoouensis Degreef (2006: 108) ( Rubiaceae ).

Habitat and ecology: —Half-shaded areas in lowland forest, frequently on the banks of forest tracks.

Phenology: —Flowering in November and February–March; immature fruits in February.

Discussion: — Sabicea ndjoleensis is similar to S. aurifodinae , S. crystallina and S. sciaphilantha ; their morphological differences are compared in the diagnosis and in Table 3. The large spathaceous bracts, completely enclosing the young flowers, are the most remarkable character of the species.

Notes: —A collection from Gabon showing similarities to both S. ndjoleensis and S. sciaphilantha is discussed under the latter species.

Conservation status:—IUCN Red List Category: Critically Endangered [CR B1ab(i,ii,iii,iv,v) + 2ab(i,ii,iii,iv,v)]. The extent of occurrence is estimated as 0.456 km 2 and the area of occupancy as 8.000 km 2, both within the limit for Critically Endangered under criteria B1 and B2. The species is known from a single location

TAXONOMIC REVISION OF SABICEA SUBGENUS ANISOPHYLLAE

Phytotaxa 293 (1) © 2017 Magnolia Press • 53 (sensu IUCN 2012), which is not protected. Forest exploitation is ongoing in the area (though currently on a limited scale) and the development of a manganese mining project a little further north is likely to bring increased human pressure on the region. A decline in the extent of occurrence, area of occupancy, extent and quality of habitat, number of locations and number of individuals is therefore expected, and the species qualifies as Critically Endangered under the conditions B1ab(i,ii,iii,iv,v) and B2ab(i,ii,iii,iv,v).

Additional specimens examined (Paratypes):— GABON. Moyen Ogooué, about 10 km NNW of Ndjolé , 16 March 1996, F.J. Breteler 13492 ( WAG) , 5–15 km NNW of Ndjolé , November 1991, F.J. Breteler & C.C.H. Jongkind 10452 ( BR, WAG) ; same locality, 15 November 1991, F.J. Breteler & C.C.H. Jongkind 10501 ( WAG) .

Figures

FIGURE 25. Sabicea ndjoleensis. A, flowering stem; B, node with stipules, reduced leaf and base of normal leaf; C, calyx surrounded by one bract seen from inside; D, portion of inflorescence with two calyces, surrounded by a bract seen from outside; E, flower bud; F, section of long-styled flower; G, long-styled flower (calyx and ovary removed); H, section of short-styled flower; I, portion of inflorescence with a short-styled flower and surrounding bract; J, detail of a hair from the corolla mouth. From Dessein et al. 2149 (A– B, E, H–J) and Breteler & Jongkind 10452 (C–D, F–G). Drawn by Hans De Vries.

FIGURE 26. Distribution of Sabicea ndjoleensis and S. parmentierae.