Gilbertiodendron newberyi Burgt

van der Burgt, X.M., Eyakwe, M. & Motoh, J. 2012. Kew Bulletin 67: 51. https://doi.org/10.1007/s12225-012-9345-9

Morphology General Habit

Tree, to 51 m high Tree, to 51 m tall

Morphology Trunk

Trunk cylindrical, to 197 cm in diam. Bark greyish brown, exfoliating in small woody flakes Trunk straight, cylindrical, to 197 cm diam. Bark greyish brown, exfoliating in small woody flakes

Morphology General Indumentum

Hairs appressed, simple, brown to light brown, to 0.2 mm long, on twig, petiole, rachis, petiolule, peduncle, flower bud and margin of young fruit; sparse hairs on young stipules and both sides of young leaflets

Morphology Leaves Stipules

Stipules in pairs in leaf axils, persistent, auriculate, 6 – 27 (– 57) mm long, 8 – 33 (– 59) mm wide Stipules in pairs, free, reniform part persistent, flat, 8 – 33 × 6 – 27 mm, sparsely puberulent to glabrescent both sides, hairs to 0.1 mm long; lanceolate part of stipule not seen

Morphology Leaves

Leaves alternate, paripinnate, sometimes imparipinnate; petiole 0.4 – 0.9 (– 1.5) cm long; rachis (0 –) 5 – 20 (– 36) cm long; petiolules 2 – 4 mm long; leaflets opposite in (1 –) 3 – 5 pairs (to 6 pairs on sterile material from juvenile trees) Leaves paripinnate, to 40 × 25 cm; petiole 4 – 10 mm long, 2 – 4 mm diam., puberulent, hairs to 0.1 mm long; leaf rachis 5 – 30 cm long, puberulent to glabrescent, hairs to 0.1 mm long, stipels absent; petiolules 2 – 4 mm long, puberulent to glabrescent, hairs to 0.1 mm long

Morphology Reproductive morphology Seeds

Mature seeds not seen

Ecology

Primary rainforest on well-drained sandy and rocky soil; 50 – 150 m. The rainfall at the Bulu weather station of the Pamol plantation, c. 12 km southeast of the type locality, averaged 5,041 mm/year (1984 – 2009). The climate is strongly seasonal with one distinct dry season from December to February (average monthly rainfall less than 100 mm). Gilbertiodendron newberyi occurs in evergreen rain forest, at 0 – 800 m asl.

Conservation

Eight groups of trees of Gilbertiodendron newberyi have been found in an area of c. 30 km2 in the southern part of Korup National Park; two of which are in plot ‘P’ (Map 2). The species was also collected 48 km to the northeast, but still within Korup National Park (D. W. Thomas 7673). This specimen is sterile but matches well the sterile and fertile samples collected in plot ‘P’. The two groups in plot ‘P’ contain five and 18 mature trees (trees over 50 cm dbh). In the other groups the trees were not counted, but the diameters of these groups were observed to be in the same range as those of the two groups in plot ‘P’. If the other groups have a population size comparable to the two groups in plot ‘P’, then the total number of mature trees present within all groups lies between 50 and 250. Therefore G. newberyi is assessed here as Endangered D under the criteria of IUCN (2001). Gilbertiodendron newberyi was assessed according to IUCN criteria as Endangered D (Burgt et al. 2012). At the recently discovered site of Burgt 1661 in the Ebo proposed National Park, two mature trees were seen, standing close to each other at the edge of old farmland. A search of two weeks around the site of Burgt 1661 did not result in the discovery of additional trees. The total number of trees known is therefore still between 50 and 250, resulting in Endangered under criterion D (Table 1).

Note

Gilbertiodendron newberyi is named after Professor David M. Newbery of the Institute of Plant Sciences, University of Bern. The new species was discovered thanks to Professor Newbery’s long-term commitment to the research on the ecology and dynamics of tree species from the Caesalpinioideae subfamily in Korup National Park. The first paper about this subject, of which he was the first author, appeared as early as 1988 (Newbery et al. 1988). The tree from which the type specimens were collected stands in plot ‘P’, the 82.5 ha permanent plot which he set up between 1990 and 1991. Professor Newbery still continues with his research in Korup National Park.

The flower bracts and bracteoles on the newly made collection Burgt 1661 are somewhat larger than those on the type; therefore the new description was adapted from Burgt et al. (2012). Gilbertiodendron newberyi resembles G. quinquejugum from Gabon, Congo (Brazzaville) and Angola (Cabinda). The main differences between the two species are found in the size of the leaves and leaflets, the size of the bracteoles, and the hairs on the bracteoles. The results of a phylogenetic study of Estrella et al. (2014) confirm the existence of two separate species. Gossweiler 7592 and 8172, named to G. quinquejugum, resemble G. newberyi in the size of the bracteoles, but the leaves and leaflets of these two collections are much smaller (see notes at G. quinquejugum).

Gilbertiodendron newberyi is named after Professor David M. Newbery of the Institute of Plant Sciences, University of Bern.

Type

Type: Cameroon, Southwest Region, Korup National Park, 12 Oct. 2005, X. M. van der Burgt 774 (holotype WAG! [WAG0204478], isotypes BR!, G!, K!, MO!, P!, SCA!, YA!).

Morphology Twigs

Twigs sparsely puberulent to glabrescent, hairs to 0.2 mm long

Morphology Leaves Leaflets

Leaflets papery, opposite, 3 – 5 (– 6) pairs, elliptic, 4 – 20 × 2 – 6 cm, smooth and glabrous both sides; somewhat glossy above, below dull, same colour or slightly lighter; midrib puberulent to glabrous both sides, prominent below; 6 – 10 pairs of lateral veins; leaflet base cuneate to obtuse, sometimes slightly oblique, apex acuminate and mucronate, acumen 0.3 – 1 cm long Leaflets elliptic, (5 –) 8 – 18 (– 25) × (2 –) 3 – 5 (– 8) cm; midrib prominent on both surfaces, 6 – 10 pairs of lateral veins; apex acuminate and mucronate with the acumen 0.3 – 1 (– 1.5) cm long; margin entire; 0 (– 1) glands at the distal margin near the base of the leaflet

Morphology General Glands

Glands 0 (– 1) per leaflet, at the proximal margin 8 – 15 mm from the apex and at the distal margin 3 – 6 mm from the petiolule

Morphology Reproductive morphology Inflorescences

Inflorescence bracts in pairs at base of lateral axes, caducous, linear part 4.5 – 7 × 1 – 1.5 mm, auriculate part 2 × 2.5 mm Inflorescence a congested, axillary or terminal cluster of 1 to several panicles, to 8.5 cm long, dark brown hairs to 0.1 mm long, internodes 4 – 8 mm long, lateral axes to 5.5 cm long, 12 – 15 flowers per cm, puberulous Inflorescences axillary or terminal clusters of panicles, to 8.5 cm long; lateral axes to 5.5 cm long, with 10 – 15 flowers per cm; bracts in pairs at base of lateral axes, caducous, linear part 4.5 – 7 × 1 – 1.5 mm, auriculate part 2 × 2.5 mm

Morphology Reproductive morphology Flowers

Flowers fragrant, floral bract inserted at base of pedicel, caducous, ovate to broadly ovate, 2 – 4 × 1.5 – 4 mm, puberulous on both sides, hairs to 0.1 mm long, centre inside sometimes glabrous; pedicel 7 – 15 mm long, densely puberulous, dense light-coloured hairs to 0.1 mm long mixed with sparse dark brown hairs to 0.2 mm long; bracteoles 2, elliptic, whitish light green, 5 – 8 × 4 – 6 mm, puberulous outside, light-coloured hairs to 0.1 mm long mixed with sparse dark brown hairs to 0.2 mm long; sparsely puberulous inside, centre inside glabrous; receptacle 1 – 1.5 mm high, 1.5 – 2 mm diam. at top, upper part glabrous, lower part with 4 patches of hairs, or a band of hairs of irregular width, hairs 0.2 mm long; sepals 5, white, glabrous, narrowly triangular, 3.5 – 5 × 1 mm, apex acute, abaxial sepal a little larger; petals 5, alternate to sepals, white, glabrous; adaxial petal claw 4 – 5 mm long, blade bilobed, 8 – 13 mm high × 10 – 19 mm wide; the other 4 petals narrowly triangular, 3.5 – 5 × 1 mm, apex acute; stamens 3, inserted alternate to the 4 small petals; filaments white, glabrous, 10 – 14 mm long; anthers glabrous, 2 – 2.5 mm long; 6 staminodes, filiform, to c. 1 mm long, inserted on a staminodal tube c. 0.5 mm long, tapering towards the top, encircling ¾ of the ovary stipe opposite the large petal; ovary light green, 3 × 1.5 × 0.5 mm, 5 – 6 ovules, margins densely hirsute, hairs brown, to 0.7 mm long, sides glabrous; stipe 0.7 mm long; style white, 10 – 14 mm long, lower part hirsute, upper part glabrous, stigma capitate Flowers: basal bract triangular, to 2 × 1.5 mm, caducous; pedicel 8 – 13 mm long, hairy; bracteoles 2, whitish light green, 5 – 6 × 4 – 5 mm, hairy on outer and inner surfaces; receptacle 1 mm high, 1.5 mm in diam. at top; sepals 5, white, glabrous, narrowly lanceolate, 3.5 × 1 mm, abaxial sepal a little larger; petals 5, alternate to sepals, white, glabrous, adaxial petal bilobed, 8 × 9 – 11 mm, the other 4 petals are similar in shape and size to the sepals; stamens 3, placed alternate to and in between the 4 small petals; filaments white, 12 – 14 mm long, glabrous; anthers brown, 2.5 mm long, glabrous; up to 6 staminodes, to 1 mm long, sometimes forked; ovary light green, brown hairs at margins, 3 × 1.5 × 0.5 mm; style 10 – 14 mm long, lower part hairy, stigma capitellate

Morphology Reproductive morphology Fruits

Fruits oblong-rectangular, brown, dull, glabrous, 1 – 3-seeded; 12 – 20 × 4.5 – 7 cm, valve 3 mm thick, beak 0 – 2 mm long, sutures not winged; 2 – 2.5 longitudinal ridges running from the base to the apex, parallel to and at 0.3 – 3 cm distance to the upper suture Fruits oblong, brown, glabrous, 12 – 20 × 4.5 – 7 cm, 1 – 3-seeded; valve 2 mm thick, sutures not winged; 2 strong longitudinal ridges running from the base to the apex, parallel to and at c. 1 and c. 2 cm distance to the upper suture, united for the first 1 – 3 cm; a weak longitudinal ridge running from the base to c. halfway to the apex, at c. 0.5 cm distance to the upper suture

Seedling

Seedlings: hypocotyl 5 – 8 cm long, epicotyl 10 – 15 cm long; first two leaves opposite, petiole and rachis 2 – 4 cm long, petiolules 1 mm long, 1 – 2 pairs of leaflets 8 – 12 × 3 – 4 cm (in reality 2 – 3 pairs of leaflets, lowest pair reduced to < 3 mm long) Seedlings: hypocotyl and epicotyl each 10 – 15 cm long; first pair of leaves opposite with 1 – 2 pairs of leaflets, petiole c. 2 cm long, rachis 0 – 2 cm, leaflets c. 10 × 3.5 cm

Distribution

Gilbertiodendron newberyi occurs in Cameroon, in the Southwest Region and the Littoral Region (Map 9). Africa, Cameroon, Southwest Region, endemic to Korup National Park (Map 1).