Gilbertiodendron maximum Burgt & Wieringa

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation

Predicted extinction risk: threatened. Confidence: confident

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, Ogooué-Maritime, 4 km on the road from Rabi to Divangui, 24 July 1992, J. J. Wieringa 1315 (holotype WAG! [WAG0070212, –218, –219, –307, –308], isotypes BR!, BRLU, BUC, C, E, EA, FHO, FR, G, IAGB, K!, LBV, LUA, MA, MO, MPU, PE, PH, PRE, RSA, UC, US).

Morphology General Habit

Tree, to 45 m tall

Morphology Trunk

Trunk to 140 cm diam. Twigs glabrescent to glabrous

Morphology Leaves Stipules

Stipules in pairs, free; caducous, flat, fan-shaped, margin dentate, 4 – 13 × 3 – 11 mm, glabrous

Morphology Leaves

Leaves paripinnate, to 38 × 29 cm; petiole 8 – 23 mm long, 2 – 4 mm diam., glabrescent or glabrous; leaf rachis 4 – 15 cm long, glabrous, stipels absent; petiolules 6 – 18 mm long, glabrous

Morphology Leaves Leaflets

Leaflets coriaceous, opposite, lower and middle pairs (sub-) opposite, 2 – 3 pairs, elliptic to obovate, 6 – 23 × 3 – 10 cm; smooth, somewhat glossy and glabrous both sides, lower surface same colour, midrib glabrous both sides, prominent below; 5 – 8 pairs of secondary veins; leaflet base cuneate to obtuse, sometimes slightly oblique; apex acute to obtuse

Morphology General Glands

Glands 0 (– 1) per leaflet, at the proximal margin near the apex and at the distal margin near the petiolule

Morphology Reproductive morphology Inflorescences

Inflorescence unknown; infructescences axillary or terminal, to 12 cm long, densely puberulous, hairs to 0.2 mm long

Morphology Reproductive morphology Flowers

Flowers unknown

Morphology Reproductive morphology Fruits

Fruits oblong-rectangular, brown, dull, glabrous, 1 – 6-seeded, 22 – 36 × 11 – 14 cm, valve 4 mm thick, beak 1 – 5 mm long, sutures not winged; 2 – 2.5 longitudinal ridges running from the base to the apex, parallel to and at 0.5 – 7 cm distance to the upper suture

Note

Gilbertiodendron maximum resembles G. ogoouense. The stipules of G. maximum are fan-shaped, not reniform as in G. ogoouense. The size of the leaflets of G. maximum is up to 23 × 10 cm; the size of the leaflets of G. ogoouense is up to 15 × 5 cm. The petiolule is 6 – 18 mm long; not 2 – 5 mm long. The size of the fruits is 22 – 36 × 11 – 14 cm, not 8 – 18 × 4 – 8 cm.

The flowers of Gilbertiodendron maximum are unknown; a flowering collection would be most welcome. However, collections of the new species can be named without doubt if there are only leaves and fruits. G. maximum can be recognised by its large petiolules, 6 – 18 mm long, which is much longer than those of the other species of Gilbertiodendron (Table 2; Aubréville 1968, 1970). A phylogenetic study by Estrella et al. (2014) places the type of G. maximum (Wieringa 1315) in the G. ogoouense species complex. G. maximum is the ninth narrow endemic described from the greater Rabi area (Wieringa & Mackinder 2012). Of these 9 endemics, 5 belong to the legume tribe Detarieae, which is a very interesting phenomenon. It seems this area constitutes a local area of endemism for this group of ectomycorrhizal trees, while for most other plants it did not develop in such a way.

The species epithet of Gilbertiodendron maximum refers to the large size of the trees from which the three known collections were made (61, 120 and 140 cm dbh), and the up to 18 mm long petiolules.

Distribution

Gilbertiodendron maximum is endemic to the Ogooué-Maritime province in Gabon (Map 4).

Ecology

Gilbertiodendron maximum occurs in evergreen rain forest on well-drained soil, at 0 – 200 m asl.

Conservation

Gilbertiodendron maximum is assessed here according to IUCN criteria as Critically Endangered B1ab(i,iii,v) (Table 1). The three localities where the species occurs are located in an area subject to logging, and are therefore considered to be one location (IUCN 2014), although it is not certain that the three localities are within the same logging concession.