Gilbertiodendron minkebense Burgt & Estrella

van der Burgt, X.M., Mackinder, B.A., Wieringa, J.J. et al. The Gilbertiodendron ogoouense species complex (Leguminosae: Caesalpinioideae), Central Africa. Kew Bulletin 70: 29. DOI https://doi.org/10.1007/s12225-015-9579-4

Type

Type: Gabon, Woleu-Ntem, Minkébé region, Sing valley, 5 km from camp site, 13 April 1990, A. Moungazi in Minkébé series AM 72 (holotype WAG! [WAG0164298, WAG0164299]).

Morphology General Habit

Tree, to 25 m tall

Morphology Trunk

Trunk to 50 cm diam. Twigs sparsely puberulent to glabrous, erect light-coloured hairs to 0.1 mm long

Morphology Leaves Stipules

Stipules in pairs, free; reniform part persistent, flat, 10 – 20 × 6 – 12 mm; sometimes to 32 × 22 × 10 mm and then a pair of stipules strongly inrolled towards each other; glabrous both sides; lanceolate part of stipule not seen

Morphology Leaves

Leaves paripinnate, to 32 × 22 cm, on juvenile trees to 50 × 35 cm; petiole 5 – 9 mm long, 3 – 4 mm diam., sparsely puberulent to glabrous; leaf rachis 3 – 20 cm long, on juvenile trees to 40 cm long, sparsely puberulent to glabrous, stipels absent; apex of rachis sometimes with a glandular-like structure; petiolules 2 – 5 mm long, sparsely puberulent to glabrous

Morphology Leaves Leaflets

Leaflets coriaceous, opposite, 2 – 5 pairs, upper pair obovate, other pairs elliptic, (5 –) 7 – 14 (– 16) × (2 –) 3 – 5 (– 8) cm (leaflets of juvenile trees to 21 × 9 cm), smooth and glabrous both sides, above somewhat glossy, below dull and same colour or slightly darker (on dried specimens); midrib prominent and glabrous above, less prominent and glabrous below; 7 – 9 pairs of secondary veins; leaflet base cuneate to obtuse, oblique; apex acuminate and mucronate, acumen 0.5 – 1.5 cm long

Morphology General Glands

Glands 1 – 2 per leaflet, at the proximal margin 7 – 22 mm from the apex and at the distal margin 5 – 8 mm from the petiolule

Morphology Reproductive morphology Inflorescences

Inflorescence a congested, axillary or terminal cluster of 1 to several panicles, to 8 cm long, densely puberulous, hairs to 0.2 mm long, internodes 6 – 9 mm long, lateral axes to 4 cm long, with 6 – 8 flowers per cm

Morphology Reproductive morphology Flowers

Flowers: floral bract inserted at base of pedicel, caducous, ovate, 3 – 4 × 2 mm, densely puberulous both sides, hairs to 0.1 mm long, centre inside glabrous; pedicel 7 – 23 mm long, densely puberulous, light-coloured hairs to 0.1 mm long; bracteoles 2, elliptic to lanceolate, 7 – 11 × 4 – 6 mm, puberulous outside, light-coloured hairs to 0.1 mm long, inside puberulous along margin, centre inside glabrous; receptacle 1.5 mm high, 2.5 mm diam. at top, glabrous or with a patch of short hairs at base outside, at abaxial side; sepals 5, glabrous, narrowly triangular, 4 – 5 × 1 – 1.5 mm, apex acute; petals 5, alternate to sepals, glabrous, adaxial petal (not fully developed) claw 5 mm long, blade bilobed, 7 mm high × 12 mm wide; the other 4 petals 4 – 5 × 0.8 mm, apex acute; stamens 3, inserted alternate to the 4 small petals; filaments glabrous, 13 – 18 mm long; anthers glabrous, 2.5 mm long; 6 staminodes, filiform, to c. 1 mm long, inserted on a staminodal tube c. 1 mm long, tapering towards the top, encircling ¾ of the ovary stipe opposite the large petal; ovary 3 × 1.5 × 0.5 mm, 3 – 4 ovules, margins densely hirsute, hairs to 0.8 mm long, sides glabrous; stipe 1 mm long; style 16 mm long, lower part sparsely hirsute, upper part glabrous, stigma capitate

Morphology Reproductive morphology Fruits

Fruits oblong-rectangular, brown, dull, glabrous, 1 – 4-seeded, 10 – 15 × 4 – 5 cm, valve 3 mm thick, beak 1 – 3 mm long, sutures not winged; 2.5 – 3 longitudinal ridges running from the base to the apex, parallel to and at 0 – 2.8 cm distance to the upper suture

Note

Gilbertiodendron minkebense is related to G. ogoouense. The leaves have a rachis of 3 – 20 cm long, and 2 – 5 pairs of leaflets. G. ogoouense has a rachis of only 2 – 7 (– 12) cm long, and (2 –) 3 pairs of leaflets. The pedicel of G. minkebense is 7 – 23 mm long and the size of the bracteoles is 7 – 11 × 4 – 6 mm. The pedicel of G. ogoouense is 6 – 11 mm long, and the size of the bracteoles is 5 – 7 × 4 – 5 mm.

The differences between Gilbertiodendron minkebense and G. ebo are given in the recognition and notes of the description of G. ebo. All collections of G. minkebense have flat stipules except one: Descoings 8591 has stipules resembling those of G. ebo, with pairs of stipules strongly inrolled towards each other (the IEC and P sheets; the MPU sheet has no stipules). Descoings 8591 is included in G. minkebense because the specimen shows several characteristics of this species: the leaflet midrib is more prominent above, the leaflet is oblique, the petiolule is 5 mm long or less, and the fruit is less than 15 cm long.

The species epithet of Gilbertiodendron minkebense refers to the Minkébé National Park in Gabon, where five collections including the type were made.

Distribution

Gilbertiodendron minkebense occurs in Gabon and in Congo (Brazzaville) (Map 7).

Ecology

Gilbertiodendron minkebense occurs in evergreen rain forest, swamp forest and riverine G. dewevrei forest, at 200 – 900 m asl.

Conservation

Gilbertiodendron minkebense is assessed here according to IUCN criteria as Vulnerable B1ab(i,iii,v) (Table 1).