Gilbertiodendron scutatum Wieringa & 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, Nyanga, 27 km N of Igotchi, 31 Oct. 2003, J. J. Wieringa 5057 (holotype WAG! [WAG0102196 – 200], isotypes ALF, BENIN!, BHO!, BP, BR!, BRVU!, CANB!, CEPEC!, DAV!, E, GC!, GZU!, K!, LBV!, MA, MBM!, MO, SL!, UB!).

Morphology General Habit

Tree, to 47 m tall

Morphology Trunk

Trunk straight, cylindrical, to 50 cm or more diam. Bark pale brown-grey with dropping flakes

Morphology Twigs

Twigs sparsely puberulent to glabrous, hairs to 0.2 mm long

Morphology Leaves Stipules

Stipules in pairs, free; reniform part persistent, green turning to brown, 15 – 48 × 10 – 40 mm, often longer than the internodes and therefore a pair of stipules often partly overlaps with the next pair, sparsely puberulent to glabrous both sides, hairs to 0.1 mm long; lanceolate part of stipule not seen

Morphology Leaves

Leaves paripinnate, to 48 × 26 cm; petiole 5 – 12 mm long, 3 – 5 mm diam., puberulent to glabrous, hairs to 0.1 mm long; leaf rachis 9 – 35 cm long, puberulent to glabrous, hairs to 0.1 mm long, stipels absent; petiolules 1 – 3 mm long, puberulent to glabrous, hairs to 0.1 mm long

Morphology Leaves Leaflets

Leaflets papery, opposite, 5 – 9 (– 11) pairs, upper pair oblanceolate, middle pairs narrowly elliptic, lowest pair elliptic, middle pairs 7 – 15 × 1.5 – 4 cm (to 25 × 6 cm on juvenile trees); above smooth, somewhat glossy, glabrous; below sparsely puberulent to glabrous, hairs to 0.1 mm long, below lighter in colour, dull, densely papillose, with a granulate cellular structure (visible only by microscope); midrib below prominent and sparsely puberulent to glabrous, hairs to 0.1 mm long; 10 – 15 pairs of secondary veins; leaflet base attenuate to cuneate, oblique; apex acuminate and mucronate, acumen 0.5 – 1.5 cm long

Morphology General Glands

Glands 0 – 2 per leaflet, at the proximal margin 10 – 20 mm from the apex and at the distal margin 2 – 4 mm from the petiolule

Morphology Reproductive morphology Inflorescences

Inflorescence a cluster of 1 to several panicles, axillary or terminal, to 19 cm long, densely puberulous, hairs to 0.3 mm long, internodes to 30 mm long; lateral axes to 11 cm long, with 8 – 10 flowers per cm

Morphology Reproductive morphology Flowers

Flowers: floral bract inserted at base of pedicel, caducous, ovate, 4 – 5 × 2.5 – 3 mm, densely puberulous outside, hairs to 0.3 mm long, puberulous inside, centre inside glabrous; pedicel 10 – 26 mm long, densely puberulous, dense light-coloured hairs to 0.1 mm long mixed with dense dark brown hairs to 0.4 mm long; bracteoles 2, elliptic, pinkish outside, white inside, 6 – 8 × 5 – 6 mm, densely puberulous outside, dense light-coloured hairs to 0.1 mm long mixed with dense dark brown hairs to 0.4 mm long; puberulous inside, centre inside glabrous; receptacle 1.5 mm high, 3 mm diam. at top, outside glabrous apart from two patches of hairs to 0.1 mm long at adaxial and abaxial side; sepals 5, white, narrowly triangular, abaxial sepal c. 6 × 3 mm, other sepals c. 5 × 2 mm, glabrous apart from a few short hairs on the margins of one or two of the sepals, apex acute; petals 5, glabrous, alternate to sepals; adaxial petal (not well seen) yellowish white, claw c. 4 mm long, blade bilobed, c. 8 mm high × 12 mm wide; the other 4 petals white, c. 5 × 1 mm, apex acute; stamens 3, inserted alternate to the 4 small petals; filaments white, glabrous, c. 9 mm long; anthers glabrous, c. 3 mm long; 6 staminodes, filiform, to c. 0.5 mm long, inserted on a staminodal tube c. 0.8 mm long, tapering towards the top, encircling ¾ of the ovary stipe opposite the large petal; ovary light green, 4 × 2 × 0.5 mm, 4 – 6 ovules, margins densely hirsute, hairs dark brown, to 0.8 mm long, sides glabrous; stipe 1 mm long; style white, 13 – 14 mm long, lower part sparsely hirsute, upper part glabrous, stigma capitate

Morphology Reproductive morphology Fruits

Fruits oblong-rectangular, brown, dull, glabrous, 0 – 5-seeded, 22 – 26 × 8 – 10 cm, valve 3 – 5 mm thick, beak 1 – 3 mm long, sutures not winged; 3 – 3.5 longitudinal ridges running from the base to the apex, parallel to and at 0.3 – 4.5 cm distance to the upper suture

Morphology Reproductive morphology Seeds

Seeds pale purple-brown, flat, to 42 × 42 × 7.5 mm

Seedling

Seedlings: hypocotyl 5 cm long, epicotyl 13 cm long; first two leaves opposite, petiole and rachis 6 – 7 cm long, petiolules 1 mm, 2 pairs of leaflets 11 – 13 × 2.5 – 4 cm (in reality 3 pairs of leaflets, lowest pair reduced to < 3 mm long)

Distribution

Gilbertiodendron scutatum is known from Equatorial Guinea and Gabon (Map 15).

Ecology

Gilbertiodendron scutatum occurs in evergreen rain forest, at 0 – 600 m asl.

Conservation

Gilbertiodendron scutatum is assessed here according to IUCN criteria as Vulnerable A2cd+3cd (Table 1). Although the Extent of occurrence is 67.300 km2, which is larger than the threshold of 20.000 km2, Vulnerable is chosen because G. scutatum is a possible timber species and most of the 11 sites are located outside protected areas.

Note

A phylogenetic study by Estrella et al. (2014) places the type of Gilbertiodendron scutatum (Wieringa 5057) in the G. ogoouense species complex, thereby confirming the results of the morphological study. G. scutatum can be recognised by its large, round and flat stipules. The width of the stipules is usually larger than the length of the internodes, therefore a pair of stipules usually overlaps with its neighbouring pairs and the twig is normally not visible. The leaves and pods of G. scutatum resemble those of G. klainei. Both species have the same number of leaflet pairs, a papillose lower leaflet surface and the same number of longitudinal ridges on the pod. However, the stipules are clearly different: G. scutatum has reniform stipules; G. klainei has linear stipules.

The species epithet of Gilbertiodendron scutatum refers to the large round stipules which have the appearance of a row of shields.

Gilbertiodendron scutatum is related to G. brachystegioides. The stipules are reniform, but flat; a pair of stipules is not strongly inrolled towards each other. The stipules are also larger in size, to 48 × 40 mm, and often longer than the internodes and therefore a pair of stipules often partly overlaps with the next pair; in G. brachystegioides the stipules are up to 30 × 20 mm and shorter than the internodes. The bracteoles are 6 – 8 mm long; not 5 – 6 mm long as in G. brachystegioides. The pods have 3 – 3.5 longitudinal ridges; not 1.5 – 2 longitudinal ridges as in G. brachystegioides.