Tessmannia korupensis Burgt, 2016

Burgt, X. M. van der, 2016, Didelotia korupensis and Tessmannia korupensis (Leguminosae, Caesalpinioideae), two new tree species from Korup National Park in Cameroon, Blumea 61 (1), pp. 51-58 : 55-58

Tessmannia korupensis Burgt , sp. nov. — Fig. 4 , 5

Morphologically comparable to Tessmannia dewildemaniana Harms ,but Tessmannia korupensis has stipules to 11 by 7 mm which have only been seen on juvenile trees; the leaflets are somewhat glossy above, with visible venation; the pedicel and the exterior surface of the sepals have dense erect hairs to 0.1 mm long, mixed with sparse appressed hairs to 0.3 mm long; the fruits are smooth,6–11 by 3.5–7 cm, the upper suture is winged,wings 5–10 mm wide on each valve. Tessmannia dewildemaniana has stipules to 25 by 13 mm, present on fertile collections;the leaflets are very glossy above with very clearly visible venation; the pedicel and sepals have dense hairs to 1 mm long; the fruits are verrucose, 4–8 by 3–5 cm, the upper suture is not wing- ed. — Type: X. M.van der Burgt 1128 (holo K (K001061190 herbarium sheet, K001061191 carpological coll.); iso BR, G, MO, P, SCA, WAG, YA), Cameroon, Southwest Region, Korup National Park, P extension plot, subplot 26ON, N5°01'04.3" E8°47'23.4", 100 m, leaves and fruits, 22 Feb. 2008.

Tree, to 39 m tall. Stem to 105 cm diam, straight, cylindrical. Buttresses to 1 m high. Bark dark grey-brown, with small vertical fissures. Twigs glabrous. Stipules caducous, not seen on mature trees; stipules on an 11 m tall juvenile tree in pairs, green, glabrous, asymmetrically ovate, 7–11 by 4–7 mm. Leaves to 28 by 22 cm, glabrous, with (2–)4–6 alternate leaflets; petiole 3–7 mm long, 2–3 mm diam; leaf rachis 5–11 cm long. Leaflets elliptic, 6–18 by 3–9 cm; petiolules 2–4 mm long; leaflet base obtuse, apex acuminate, to 10 mm long; both sides slightly glossy and identical in colour, or slightly darker below; 8 –12 pairs of secondary veins. Leaflets dotted with translucent dots, one dot of 0.2 mm diam and 3–10 dots c. 0.1 mm diam in each areole. Glands 5–12 per leaflet, 0.25–0.4 mm diam, placed near the petiolule and near the margin. Inflorescence unknown. Flowers: bract at base of pedicel not seen; bracteoles 2, caducous, not seen, inserted at 0–1 mm and 2–4 mm from the base of the pedicel; pedicel green, 18–38 mm long, puberulent, dense erect hairs to 0.1 mm long, mixed with sparse appressed hairs to 0.3 mm long; sepals 4, outside green, puberulent, dense erect hairs to 0.1 mm long, mixed with sparse appressed hairs to 0.3 mm long; inside densely hirsute with appressed hairs to 1 mm long; edges glabrous; the adaxial sepal broadly elliptic, consisting of two fused sepals, apex often split, 12–17 mm long by 10–12 mm wide; the other 3 sepals narrowly elliptic, 12–17 by 5–8 mm; petals 5, alternate to the sepals, pink; oblanceolate, adaxial petal c. 25 by 10 mm, the other 4 petals 35–40 by 15–20 mm, including claw of 5 – 8 mm long; midvein of petals densely appressed hairy on both sides, hairs light brown, to 2 mm long, mature petals glabrescent; stamens 10, in two whorls of 5, the adaxial stamen free, the proximal 2–4 mm of the filaments of the other 9 stamens united; filaments pink, outer 5 filaments 32–40 mm long, inner 5 filaments 25–30 mm long; lower 5 mm of filaments densely appressed hairy, hairs light brown, to 2 mm long, mature filaments glabrescent;anthers orange, c. 5 by 1 mm, glabrous; ovary light brown, c. 12 by 5 by 2 mm, densely hirsute, light brown hairs to 1 mm long; 4–5 ovules; stipe 2 mm long, densely hirsute; style pink, 22– 28 mm long, glabrous; stigma capitate. Infructescence unknown. Fruits obovate, dull, dark brown, smooth, puberulent, erect hairs to 0.3 mm long, woody, 6–11 by 3.5–7 cm, valve 2–3 mm thick, stipe 6–8 mm long, upper suture winged, 5 –10 mm wide on each valve, beak 2–4 mm long; fruits contain 1–2 seeds and are explosively dehiscent. Seedlings : hypocotyl 10–15 cm, epicotyl 4.5–8 cm long, both with sparse hairs to 0.1 mm; first two leaves opposite, petiole 0.8–2 cm long, sparse hairs to 0.1 mm; 1 pair of opposite leaflets 6–9 by 2.5–3.5 cm, glabrous; petiolules 1–2 mm long, sparse hairs to 0.1 mm.

Distribution — Endemic to the Southwest Region in Cameroon ( Fig. 3 ); recorded in and near the permanent plots along the P transect in the southern part of Korup National Park and from a single collection made in the lowland rain forest on the western side of Mt Cameroon at c. 75 km distance to the type locality.

Habit — Canopy tree from rain forest. The bark has small vertical fissures ( Fig. 5b ), similar to the bark of the other species of Tessmannia .

Habitat — Rain forest dominated by trees in the Detarieae tribe of the Legume subfamily Caesalpinioideae , on well-drained sandy and sometimes rocky soil, at 100–200 m altitude.

Additional material. CAMEROON, Southwest Region, Korup National Park, P extension plot, subplot 24UN, trees PE8293 and PE8295, N5°00'55.0" E8°47'25.9", 100 m, fruits, X. M. van der Burgt 707 (BR, G, K, MO, P, SCA, WAG, YA), 7 Sept. 2004 ; subplot 24UN, tree PE8293, flowers, X. M. van der Burgt 943 (K, MO, WAG, YA), 25 May 2007; near P transect, c. 1.5 km south of Science Camp ,along the stream passing through the camp, sterile, X. M. van der Burgt 1123 (BR, G, K, MO, P, SCA, WAG, YA), 19 Feb. 2008 ; Southwest Region, Mt Cameroon, Liwenyi, around Likenge village , sterile, P. Tchouto 515 (K), 18 Mar. 1993 .

Conservation status — Tessmannia korupensis is assessed here according to IUCN (2015) criteria as Endangered, EN B1ab(i,iii). The new species has an Extent of Occurrence of c. 230 km 2. Much of the forest between the two known occur- rences has been or will be converted to farmland or oil palm plantations. This area has been much less visited by botanists but the species likely occurs here as well, indicating the possibility of continuing decline in the sense of IUCN criteria. At Liwenyi, around Likenge village, in the Onge forest, where the species was collected in 1993, slash and burn agriculture was then a threat to the forest (Cheek pers. obs. 1993). The threat of large-scale forest clearing for oil palm plantation exists for all unprotected forest in Cameroon. Korup National Park un- fortunately is not fully protected; some of the residents of the villages around the park use parts of the park for hunting and farming. In September 2009, the four camps for researchers and tourists in southern Korup were burned down by local villagers in protest of the prohibition of hunting and farming within the park. Although the forest does not burn naturally, the same fate might happen to parts of the forest during a dry season with exceptionally dry weather.

Notes — Trees have been recorded inside and near the permanent plots along the P transect in the southern part of Korup National Park. These plots have a total area of 155.75 ha. Of the 3 181 registered trees ≥ 50 cm stem diam in the plots, only two trees, standing at 10 m distance to each other, were identified as T. korupensis . Trees between 10 and 50 cm diam were registered in 56 random located subplots within the plots (area of each subplot 0.25 ha; total area of all 56 subplots 14 ha). None of the 5 755 registered trees between 10 and 50 cm diam were identified as T. korupensis . Most of the forest in southern Korup does not contain any T. korupensis trees.

Tessmannia korupensis trees always occur in groups; seven such groups of trees have been recorded in southern Korup, at distances of 0.3–6.4 km to each other. One of these groups was mapped and found to contain 43 individuals over 10 cm stem diam, in an area of less than 1 ha ( Fig. 6 ), mixed with many trees of other species. In two other groups the trees were counted: 9 trees and 33 trees over 10 cm stem diam.

The pods of T. korupensis curl up when dry ( Fig. 4j ), indicating the presence of ballistic seed dispersal ( Van der Burgt 1997). Even though the trees are tall, the maximum seed dispersal distance (which could not be recorded) will be small compared to that of most other species in the Legume tribe Detarieae because the fruits are small; see remarks under Didelotia korupensis . Most other species in the genus Tessmannia have small cardboard-like pods which stay flattened when dry and are therefore not constructed for ballistic seed dispersal.

A number of specimens, usually collected in or near Gabon, do not match any of the existing species of Tessmannia . This material may represent several new species (F.J. Breteler pers. comm.), and is already cited in Sosef et al. (2006) under four different unpublished names. These species will be formally published in a future article. The type of T. korupensis does not match the collections cited in Sosef et al. (2006) under these four undescribed species.

Tessmannia korupensis can be distinguished from all other species of Tessmannia by its comparatively large pods of 6 –11 by 3.5–7 cm with its upper suture with 5–10 mm wide wings on each valve. Other species of Tessmannia have pods of 3–8 by 2–5 cm and lack wings.

Figures

Fig. 4 Tessmannia korupensis Burgt. a. Twig with three leaves; b. section of twig with pair of stipules and leaf base; c. apex of leaflet upper surface; base of leaflet lower surface, showing glands; d. leaflet lower surface; e, f. flower; g. diagram of flower; h. pod; i. dry pod valves (a, c, d, h, i. Van der Burgt 1128, K, WAG; b. Van der Burgt 1123, K; e–g. Van der Burgt 943, K). — Drawn by Xander van der Burgt.

Fig. 5 Tessmannia korupensis Burgt. a. Stem of a tree of 52 cm diam at 1.3 m above ground; b. bark; c. lower surface of leaflet with translucent dots; 6 by 4.5 mm (Van der Burgt 1128, K). — Photos by Xander van der Burgt.

Fig. 3 Distribution of Didelotia korupensis Burgt (only the upper black circle) and Tessmannia korupensis Burgt (both black circles).

Fig. 6 Map of a group of 43 trees of Tessmannia korupensis Burgt in southern Korup National Park. The size of a dot represents the stem diam at 1.3 m above ground in 7 size classes: 10–20 cm to 70–80 cm. The group is divided by a river bordered on one side by swamp forest. All trees grow on well-drained soil; T. korupensis is not a river bank tree species.The area on the map is completely covered by closed-canopy rain forest.