Sabicea bullata Zemagho, O.Lachenaud & Sonké, 2014

Zemagho, Lise A., Lachenaud, Olivier, Dessein, Steven, Liede-Schumann, Sigrid & Sonke, Bonaventure, 2014, Two new Sabicea (Rubiaceae) species from West Central Africa: Sabicea bullata and Sabicea urniformis, Phytotaxa 173 (4), pp. 285-292 : 289-290

Sabicea bullata Zemagho, O.Lachenaud & Sonké , sp. nov. ( Fig. 3 )

Type:— CAMEROON. Rumpi Hills near Dikome Balue, 1417 m, 4°54’53.7’’ N 09°14’32.3’’ E, 18 April 2009, Dessein et al. 2572 (holotype BR; isotype YA) .

Creeping or twining liana; stems up to 3 m long; 0.5-3 mm thick; twigs hirsute with long straight hairs (1–2 mm long); only the twining stems are flowering. Stipules persistent, entire, ovate to sub-orbicular, acute at the top, 8–12 × 8–10 mm, glabrous on adaxial surface, hirsute on the abaxial surface. Leaves opposite, equal; petioles 0.5–4.5 cm long, hirsute (hairs c. 2 mm long); blades elliptic, 4.8–11 × 2.8–6.5 cm, green on both surfaces (the young leaves tinged purple below), hirsute on both surfaces, margins ciliate (hairs 0.7–1 mm long), strongly bullate in vivo (not always visible when dry); base cordate; apex acuminate; secondary nerves 10–15 on each side of the mid-vein. Inflorescences solitary at the nodes, glomerulate, 3–5-flowered, sessile; bracts green, broadly ovate to narrowly ovate, apex acute, hirsute on both surfaces; 5–7 × 2–6 mm, free, rather inconspicuous and not clearly forming an involucre, consisting of one basal pair and one pair below each flower. Flowers 5-merous, sessile; only longistylous flowers known. Calyx green, tube ca. 1 mm long, lobes ovate to narrowly ovate, 7–9 × 4–5 mm, apex acute, hirsute outside, glabrous inside except near base. Corolla white, tube 12–15 mm long, lobes 2–3 mm long, appressed-pubescent outside, pubescent inside above the insertion of the stamens. Stamens included, inserted near the middle of the tube; anthers ca. 2 mm long, base and apex glabrous. Ovary 5-locular; style 5-lobed, exserted, stigmas ca. 2 mm long (long-styled flowers). Fruits sessile, ovoid, 7 × 5 mm (probably larger when fully mature), hirsute, red, topped with green persistent calyx. Seeds, numerous, not mature.

Distribution and Ecology: — Sabicea bullata is endemic to the western Cameroon highlands (Rumpi Hills and Bakossi Mountains) ( Fig. 2). It occurs in submontane forest, 1000–1417 m a.s.l. The species is relatively light demanding, occurring mostly in edges and treefall gaps, and avoiding dark undergrowth. It is locally very abundant and can cover the ground on forest paths. It is generally encountered as a sterile creeper; only the twining stems bear flowers, which explains the rarity of collections.

Phenology:—Flowers: January. Mature fruits: April.

Notes:—The species was already recognized as new (as Sabicea sp. A ) by Cheek et al. (2004). This is a rather isolated species, with no obvious close relatives. The leaves of Sabicea bullata , which are cordate at base and strongly bullate in life (hence the specific name), make the species easily recognizable even when sterile. The leaves of Sabicea leucocarpa (K.Krause) Mildbraed ( Krause 1917: 357; Mildbraed 1922: 91) are also cordate at the base, but not bullate; the species further differs from Sabicea bullata in pedunculate and involucrate inflorescences, white fruits, and lowland habitat. Although only one flowering collection is known, the species is presumably heterostylous, as usual in the genus.

Conservation status:—The species is known from four collections only, all from western Cameroon. The thresholds for Endangered under Criterion B are met for Extent of Occurrence (123.89 km 2) and Area of Occupancy (12 km 2, grid cell size 2 km). It is difficult, however, to define a clear threat for the species at present. Although there are clear signs of forest degradation in both the Bakossi Mountains and the Rumpi Hills, it is not obvious at present how this will influence the survival of Sabicea bullata . Indeed, most Sabicea species , including this one, survive well in degraded forests. Therefore the species is for now considered as Least Concern.

Paratypes:— CAMEROUN: Bakossi Mountains 1–8 km NNE of Meyum Village, 20–30 May 1987, Doumenge 474 (MO, YA); Kodmin , 21 January 1998, Etuge et al. 4061 (MO, YA); Rumpi Hills near Dikome Balue, 1204 m, 21 April 2009, Dessein et al. 2651 (BR, K, MO, YA) .

Figures

FIGURE 3. Sabicea bullata. A. Habit. B. Bract C. Long-styled flower. D. Calyx with 2 bracteoles. E. Infrutescence with bracts and two stipules. A–B & D–E, Dessein et al. 2572; C, Etuge 4061.