Typus: GABON. Moyen-Ogooué: Mabounié, 0°46′31″S 10°32′30″E, 2.XI.2014, Lachenaud, Bidault & Lissambou 2116 (holo-: BRLU!; iso-: BR!, G!, LBV!, MO!, P!, WAG!).

Low creeping herb, 5–15 cm high, with stems rooting at base; stems villous, with indumentum consisting of c. 2 mm long, pinkish, patent hairs, intermingled with much shorter uncinate hairs. Leaves opposite, highly unequal especially on upper nodes, often appearing alternate at first sight; reduced leaf with petiole 0-1 cm and lamina lanceolate to elliptic, 1.2–6.3 × 0.3–2.9 cm; normal leaf with petiole 1.2–3.2(-5.5) cm long, with similar indumentum to the twigs, and lamina (5.8-)8-13.8 × (2.2-)3.7-6.5 cm, elliptic, acute to obtuse and often asymmetrical at base, acuminate at apex, papery and strongly discolorous; upper side green, with appressed stiff hairs very sparse on the lamina and denser on the nerves, where they are intermingled with shorter crisped hairs; lower side pinkish-buff with dense persistent felt of woolly hairs (becoming sparser but still visible on old leaves), intermingled with long stiff appressed hairs on the nerves and on the margin; nerves slightly bullate above, pinkish beneath, the laterals 9–12, ascending and almost reaching the margin; tertiary veins densely reticulate and contrasting below. Stipules wine red, 2 per node, interpetiolar, erect to patent, 12-23 × 3.5-10.5 mm, broadly ovate and slightly falcate, acute, entire or with 1–2 short lateral teeth, slightly veined, sparsely hairy outside with +/- appressed hairs 0.3–1 mm long, glabrous inside. Inflorescences axillary, solitary at each node and borne in the axil of the reduced leaf, densely glomerulate to very shortly cymose, 1.3–1.7 cm long; peduncle very short and usually hidden by the stipules, 0.2–0.5 cm long, with same indumentum as the stems; flowering part 1.2–1.4 × 1.7-2.3 cm; ramifications not or hardly distinct, < 0.1 cm. Bracts wine red, numerous, decreasing in size from the base to the apex of the inflorescence, not clearly forming an involucre, entire or shortly dentate, sparsely appressed-hairy outside, glabrous or with very sparse short hairs near the apex inside; lower pair of bracts broadly ovate, shortly connate at base for c. 1 mm and acute at apex, 11–11.5 × 5–7 mm; upper bracts lanceolate, free, acute, 6-11 × 0.5-2.5 mm, resembling the calyx lobes. Flowers (4-)5-merous; pedicels very short, < 1 mm long, densely hairy. Calyx wine red, with short tube c. 1 mm; lobes acute, narrowly lanceolate, erect to oblique at anthesis and +/- bending outwards at apex, 5-6 × 0.6-1 mm, sparsely hairy outside with hairs 0.5–1.5 mm long, glabrous inside except short sparse hairs near their apex, alternating with short colleters at their base. Corolla pale buff in bud, pure white at anthesis and later fading to brown; tube narrow and almost cylindrical, 6 × 1.5 mm; lobes triangular, patent, 2 mm long; outside of corolla with short, c. 0.5 mm long stiff hairs on lobes and upper l/4th of tube, otherwise glabrous; inside of corolla with a dense beard of (0.7-)1-1.2 mm long moniliform hairs in throat and upper part of tube, and a separate ring of shorter hairs inside the tube just above mid-height. Stamens included, inserted c. 1.5 mm below throat of corolla tube; anthers subsessile, c. 1 × 0.3 mm, shortly apiculate. Ovary c. 2 mm long, densely covered with long appressed stiff hairs, 2-locular in cross-section. Disk shortly cylindrical, c. 0.5 mm, glabrous. Style bifid, included, about equalling the anthers, glabrous, 5.5 mm long including the 1.5 mm long stigmas, these dorsally compressed and rounded at apex. Fruits dark purple outside, with purple flesh, ovoid, with persistent calyx, 12-17 × 8-11 mm in life, villous with patent hairs 1-2 mm long, very shortly pedicellate (pedicel c. 1 mm long). Seeds numerous, dark brown, polygonal, c. 1 × 0.5 mm, the surface with dense parallel striations.

Etymology. — The species is named after Golgotha Hill in the Mabounié region, where it was first discovered, and in the vicinity of which all known subpopulations occur.

Distribution and ecology. — Sabicea golgothae is apparently endemic to the Mabounié region in West-Central Gabon (Fig. 4), where it is known from three very close sites. The new species grows in half-shaded forest edges along tracks, where it locally forms dense populations.

Conservation status.—The. EOO of S. golgothae is estimated as 0.608 km² and the AOO as 12 km², respectively within the thresholds for “Critically Endangered” and “Endangered” under Criteria B1 and B2. The species is known from three subpopulations (in addition to the two subpopulations from which specimens were taken, a third was observed at 0°46′09″S 10°32′07″E) which represent a single location in the sense of IUCN, and all three occur in the mining concession. One of these subpopulations at least is under immediate threat in the mining project. A decline in the EOO, AOO, extent of habitat and quality, number of subpopulations and number of individuals can therefore be predicted. Sabicea golgothae should thus be assigned a preliminary status of “Critically Endangered” [CR B1ab(i,ii,iii,iv,v)].

Notes. — Sabicea golgothae is very close to S. mabouniensis described below. Both species also resemble S. medusula K. Schum, ex Wernham, S. mildbraedii Wernham, and S. sthenula (N. Hallé) Razafim. et al. All these species have in common a low creeping habit, strong anisophylly (in S. sthenula and some rare variants of S. mildbraedii, the anisophylly is even extreme, with a single leaf per node) and a 2-locular ovary. The major differences between them are summarised in Table 1.

Sabicea medusula, S. mildbraedii and S. sthenula all differ from S. golgothae in having truly sessile inflorescences, and a green to whitish calyx. In S. golgothae the peduncle, although short, is always present, and the calyx is wine red; the fruits are also conspicuously larger than in the three other species.

From S. mabouniensis, S. golgothae can be distinguished by the acute to obtuse (not cordate) leaf bases, strongly discolorous leaves (with the indumentum completely obscuring the under surface, except on old leaves), more condensed inflorescences with shorter peduncles, the deep wine red colour of its bracts and calyces, and the entirely white corollas with longer hairs in the throat. These differences are slight, but appear to be constant in the subpopulations we have seen. Since the two taxa occur in the same area, only a few kilometers away from each other, and without apparent habitat discontinuity or barriers to dispersal, it seems appropriate to treat them as separate species rather than subspecies. The apparent difference in the internal indumentum of the corolla tube between S. golgothae (two separate rings of hairs) and S. mabouniensis (a single continuous ring) may not be significant, since we have found other Sabicea species (e.g. S. mildbraedii) to be variable in this respect.

The flowers of S. golgothae, with their anthers and style at same level, appear to be isostylous. This would be exceptional in a genus where distyly is otherwise the rule. However, since only the type collection bears open flowers, more material would be needed to confirm this character.

Paratypus. - GABON. Moyen-Ogooué: Mabounié, Golgotha, 0°45′55″S 10°32′49″E, 31.X.2014, Lachenaud, Bidault & Lissambou 2106 (BR, BRLU, LBV, MO).

Typus: GABON. Moyen-Ogooué: Mabounié, piste du nord-est, 0°43′00″S 10°35′53″E, 17.XI.2013, Lachenaud, Stévart, Ikabanga, Issembé, Boupoya & Kaparidi 1446 (holo-: BR!; iso-: BRLU!, LBV!, MO!, P!,WAG!).

Habitu reptante, foliis valde anisophyllis, ovarioque biloculare Sabicea golgothae O. Lachenaud & Xemagho, S. medusula K. Schum, ex Wernham, S. mildbraedii Wernham et S. sthenula (N. Hallé) Razafim. et al. similis est; sed a primo differt foliis basi cordatis indumento subtus laxiore, pedunculis longioribus (0.8–2 nec 0.2–0.5 cm), calyce viride (nec rubro), corolla lobis intus ochraceo-luteis et fauce breviore barbata; ab alteris speciebus inflorescentiis pedunculatis, foliis indumento subtus laxiore et lamina non obscurante, corollaeque lobis intus ochraceo-luteis (nec albis) conspicue distinguitur.

Low creeping herb, with stems rooting at base; stems villous with indumentum consisting of 1.5–2 mm long, pinkish, patent hairs, intermingled with much shorter uncinate hairs. Leaves opposite, strongly unequal especially on upper nodes, often appearing alternate at first sight; reduced leaf with petiole 0–1.3 cm and lamina lanceolate to elliptic, 1.1-3.6 × 0.3-2.6 cm; normal leaf with petiole 2–4 cm long, with similar indumentum to the twigs, and lamina 7-13.2 × 4.2-7.3 cm, elliptic, subcordate and asymmetrical at base, acuminate at apex, papery and slightly discolorous; upper side green, with appressed stiff hairs very sparse on the lamina and denser on the nerves, where they are intermingled with shorter crisped hairs; lower side pale green, with short and rather sparse pinkish-white woolly hairs, intermingled with longer hairs on the nerves; nerves slightly bullate above, pinkish beneath, the laterals 9–12, ascending and almost reaching the margin; tertiary veins densely reticulate and slightly contrasting below. Stipules pinkish-green, 2 per node, interpetiolar, erect, A12-18 × 6-9 mm, broadly ovate and slightly falcate, acute, entire or shortly bidentate, faintly veined, sparsely hairy outside with appressed hairs c. 1 mm long, glabrous inside. Inflorescences axillary, usually in opposite pairs but sometimes only one developing per node, in dense contracted cymes (often appearing falsely umbellate), 1.8–4 cm long; peduncle 0.8–2 cm long, with similar indumentum to the twigs; flowering part 1-2 × 1.4-2.7 cm; ramifications short, < 0.4(-1) cm. Bracts pale green, numerous, decreasing in size from the base to the apex of the inflorescence, not clearly forming an involucre, free or shortly connate at base for c. 1.5 mm, entire, rather densely appressed-hairy outside and sparsely so inside; lower bracts broadly ovate, acute, 10-13 × 3-6 mm; upper bracts narrowly lanceolate, c. 8 × 1.2 mm, resembling the calyx lobes. Flowers 5-merous, pedicels 1–2 mm long, densely hairy. Calyx pale green (the apex of lobes often pinkish), with tube very short, c. 0.5 mm; lobes acute, narrowly lanceolate, +/- patent at anthesis, 5-6 × 0.6 mm, densely hairy outside and sparsely so inside, alternating with short colleters at their base. Corolla with white, narrow and almost cylindrical tube, 6 × 1-1.5 mm; lobes pale ochre-yellow inside, triangular, patent, 1.3–1.7 mm long; outside of corolla with short, c. 0.5 mm long appressed hairs on lobes and upper l/5th of tube, otherwise glabrous; inside of corolla sparsely hairy in upper half of tube and more densely so around the throat, with rather short moniliform hairs c. 0.5 mm long. Stamens included with apex almost reaching throat; anthers sessile, 1.3 × 0.5 mm, shortly apiculate. Ovary c. 2 mm long, densely appressed-hairy, 2-locular. Disk shortly cylindrical, c. 0.3 mm, glabrous. Style bifid, included, reaching about the mid-height of anthers, glabrous, 5 mm long including the 1.5 mm long stigmas, these dorsally compressed and rounded at apex. Fruits unknown.

Distribution and ecology. — Sabicea mabouniensis is known from a single site in the Mabounié area, in West-Central Gabon (Fig. 4). It is apparently a very rare species: although the area has been relatively well-prospected in recent years, no other sites were found. The species grows on a sunny forest edge along a track, a common habitat for species of the genus. It occurs there alongside another new species of Sabicea (Lachenaud et al. 1447); the latter is not strictly endemic to the region, and will be described elsewhere.

Conservation status. - The new species is known from a single subpopulation, representing a single location, and occurs in a mining concession. The AOO of S. mabouniensis is estimated at 4 km², within the threshold for Critically Endangered status under Criterion B2 (the EOO is not calculable). It is thus extremely susceptible to any threat, the most important of which is deforestation for mining. Although the area where it occurs is not to be immediately affected by the mining project, we anticipate that this pressure will increase in the future. A decline in the AOO, extent and quality of habitat, number of subpopulations and number of individuals can therefore be expected, and the species should thus be assigned a preliminary status of “Critically Endangered” [CR B2ab(ii,iii,iv,v)].

Notes. — Sabicea mabouniensis is morphologically very close to S. golgothae, also described in this article (see under that species for more details). It also superficially resembles other low anisophyllous species (S. medusula, S. mildbraedii and S. sthenula) but is quite easily separated by the pedunculate inflorescences, the weakly discolorous leaves with hairs not obscuring the under surface (vs. strongly discolorous with a dense felt of woolly hairs obscuring the under surface), and the corolla with short hairs in the throat and lobes ochre-yellow inside (vs. corolla long-bearded in the throat and with the lobes entirely white) (Table 1).

Only short-styled flowers have been observed in S. mabouniensis. Due to the rarity of the material, it is not possible to determine whether the species is heterostylous, as usual in the genus.