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
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Type
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Type: Gabon, Ogooué-Lolo, about 30 km E of Lastoursville, near Bambidie, 7 Oct. 1997, F. J. Breteler & M. E. Leal 14250 (holotype WAG! [WAG0090697, WAG0090698], isotypes BR!, BRLU, E, K!, LBV!, M, MA, MO, NY, P, US).
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Morphology
General
Habit
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Tree, to c. 40 m tall
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Morphology
Trunk
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Trunk straight, to 80 cm diam. Twigs puberulent, hairs erect, to 0.3 mm long
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Morphology
Leaves
Stipules
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Stipules in pairs, free; reniform part persistent, flat, 12 – 25 × 8 – 20 mm, sparsely puberulent both sides; lanceolate part of stipule early caducous, c. 11 × 1 mm
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Morphology
Leaves
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Leaves paripinnate, to 40 × 25 cm; petiole 5 – 9 mm long, 2 – 5 mm diam., puberulent, hairs 0.2 mm long; leaf rachis 5 – 18 (– 26) cm long, puberulent, stipels absent; petiolules 2 – 5 mm long, puberulent, hairs to 0.2 mm long
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Morphology
Leaves
Leaflets
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Leaflets somewhat coriaceous, opposite, 3 – 6 pairs, narrowly elliptic, 5 – 14 (– 18) × 2 – 4 (– 5.5) cm, above smooth and somewhat glossy with prominent venation, below dull, lighter in colour, densely papillose, with a granulate cellular structure (visible only by microscope); above glabrescent to glabrous, below sparsely persistent puberulent, hairs appressed, to 0.1 mm long; midrib sparsely puberulent both sides, below prominent; 7 – 10 pairs of secondary veins; leaflet base cuneate to obtuse, slightly oblique; apex acuminate and mucronate, acumen 0.5 – 1.5 cm long
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Morphology
General
Glands
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Glands 0 – 1 (– 3) per leaflet, at the proximal margin 1 – 18 mm from the apex and at the distal margin 2 – 5 mm from the petiolule
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Morphology
Reproductive morphology
Inflorescences
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Inflorescence a congested, axillary or terminal cluster of 1 to several panicles, to 7 cm long, densely puberulous, hairs to 0.3 mm long, internodes 4 – 8 mm long; lateral axes to 4 cm long, with c. 10 flowers per cm
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Morphology
Reproductive morphology
Flowers
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Flowers: floral bract inserted at base of pedicel, caducous, broadly ovate, 3 × 3 mm, densely puberulous outside, light-coloured hairs to 0.2 mm long mixed with a few dark brown hairs to 0.3 mm long, puberulous inside near margins, centre inside glabrous; pedicel 3 – 8 mm long, densely puberulous, dense light-coloured hairs to 0.2 mm long mixed with dense dark brown hairs to 0.4 mm long; bracteoles 2, elliptic, greyish green, 8 – 9 × 5 – 6 mm, densely puberulous outside, dense light-coloured hairs to 0.2 mm long, sparse dark brown hairs to 0.3 mm long at base and along margins; sparsely puberulous inside near apex and margins, hairs to 0.2 mm long, centre inside glabrous; receptacle 1.5 mm high, 3 mm diam. at top, a band of hairs 1 mm wide outside at base, upper part glabrous; sepals 5, white, glabrous except for a few hairs on lower margins of abaxial sepal, narrowly triangular, 5 × 2.5 – 3 mm, apex acute, margins with a few teeth; petals 5, alternate to sepals, white, glabrous, adaxial petal claw 5 – 7 mm long, blade bilobed, 6 mm high × 10 mm wide; the other 4 petals 4 – 5 × 2 mm, margins incised, apex acute; stamens 3, inserted alternate to the 4 small petals; filaments white, glabrous, 19 – 22 mm long; anthers glabrous, 2 – 2.5 mm long; 6 staminodes, filiform, to c. 2 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 light green, 4 × 2 × 0.5 mm, 5 – 6 ovules, margins densely hirsute, hairs to 0.8 mm long, sides glabrous, stipe 1 mm long; style 13 – 17 mm long, lower part sparsely hirsute, upper part glabrous, stigma capitate
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Morphology
Reproductive morphology
Fruits
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Fruits oblong-rectangular, brown, dull, glabrous, 1 – 3 -seeded, 10 – 21 × 5 – 7 cm, valve 3 mm thick, beak 2 – 3 mm long, sutures not winged; 2 – 2.5 longitudinal ridges running from the base to the apex, parallel to and at 0.3 – 2.8 cm distance to the upper suture
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Seedling
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Seedlings: hypocotyl 4 – 8 cm long, epicotyl 7 – 11 cm long; first two leaves opposite, petiole and rachis 2 cm long, petiolules 1 mm long, 1 – 2 pairs of leaflets 9 – 11 × 3.5 – 4 cm (in reality 2 – 3 pairs of leaflets, lowest pair usually reduced to < 3 mm long, sometimes up to 3 × 1 cm)
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Distribution
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Gilbertiodendron breteleri is endemic to Gabon (Map 11).
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Ecology
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Gilbertiodendron breteleri occurs in evergreen rain forest; at 300 – 600 m asl.
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Conservation
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Gilbertiodendron breteleri is assessed here according to IUCN criteria as Vulnerable B1ab(i,iii,v) (Table 1). Although the Extent of occurrence is 24.100 km2, which is larger than the threshold of 20.000 km2, Vulnerable is chosen because G. breteleri is a possible timber species and 9 of the 10 sites are located outside protected areas.
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Note
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klainei or G. scutatum (1 sheet; barcoded with a number out of sequence). Presumably this is a curation error. Most collections of Gilbertiodendron breteleri, including the type, were collected in the Lastoursville area. There are currently 25 plant species known to be endemic to this area (Wieringa & Mackinder 2012; Velzen & Wieringa 2014), which is a considerable number. This adds support for the creation of a protected area in this part of Gabon.
This is an important difference with G. quinquejugum, of which the leaflets beneath are smooth and somewhat glossy. The lower surface of the leaflets of G. breteleri appears dull and lighter in colour than the upper surface; while the lower surface of the leaflets of G. quinquejugum appears identical or slightly lighter in colour than the upper surface. This difference is obvious on the leaflets of the flowering collections Breteler 14250 and 15510, but less well visible on the leaflets of the juvenile trees of Wieringa 6099, 6190 and 6191. Presumably the papillose character of the leaflets only develops well in leaflets exposed to full sunlight at the outer canopy. Four sterile collections, Reitsma 1203, 2480, 2724 and Wilks C 118, show the papillose lower leaflet surface and are therefore identified to G. breteleri. Two sterile collections, Breteler 11367 and Wieringa 7559, are placed in G. breteleri because they have been collected near the type locality; they might also be G. quinquejugum, although this species is not known from the Ogooué-Lolo province.
A phylogenetic study by Estrella et al. (2014) places the type of Gilbertiodendron breteleri (Breteler 14250) in the G. ogoouense species complex, thereby confirming the results of the morphological study. This study also confirms that Wieringa 6099, 6190 and 6191 are conspecific with the type of G. breteleri.
The species epithet of Gilbertiodendron breteleri refers to Frans J. Breteler, who collected the type specimen together with Miguel Leal. From his base at the WAG Herbarium in Wageningen, The Netherlands, Frans Breteler has been studying the flora of Gabon for many years. The new species was discovered thanks to the two excellent flowering collections which he made.
Gilbertiodendron breteleri is related to G. quinquejugum. The rachis is somewhat longer, 5 – 18 (– 26) cm long; not 3 – 16 cm long. The leaflets are somewhat larger, up to 14 (– 18) × 4 (– 5.5) cm; not up to 12 × 4 cm. The leaflets of G. breteleri are dull and densely papillose below, with a granulate cellular structure (visible only by microscope), not somewhat glossy and smooth as in G. quinquejugum. The leaflets of G. breteleri are also sparsely persistent puberulent below, with hairs to 0.1 mm long; not glabrescent to glabrous. The pedicel is 3 – 8 mm long; not 8 – 15 mm long as in G. quinquejugum.
