Talbotiella bakossiensis Cheek ex Mackinder, Wieringa & Burgt

Sonké, Bonaventure, Simo-Droissart, Murielle, Bidault, Ehoarn, Ngoula, Fernandez & van der Burgt, Xander M, 2024, Talbotiella couteronii (Leguminosae: Detarioideae), a new gregarious tree species from Cameroon, Plant Ecology and Evolution 157 (3), pp. 407-416 : 407-416

Talbotiella bakossiensis Cheek ex Mackinder, Wieringa & Burgt

Fig. 1 , Table 1

Type.

CAMEROON – Southwest Region • Bakossi Mts, Mwanzum to Kodmin between hut 1 and 2 ; 4°59’N, 9°40’E; 1350 m; 18 Nov. 1998; Cheek 9688; holotype K n. v.; isotypes: P n. v., WAG [ WAG 0248233 ] image, YA n. v .

Description.

Tree up to 29 m high, stem up to 74 cm diameter; bole weakly 5 - fluted (Cheek 10382; see original description), base with small buttresses; bark smooth to slightly rough; outer slash thick with dark outer line, dull orange, granular-sandy; inner slash pale orange-yellow, fibrous; crown dense. Twigs moderately to densely pubescent, hairs 0.5–1 mm long. Bud scales 5–10, caducous, distichous, brown, coriaceous, not keeled, outer and inner surface glabrous, proximal scale orbicular, ca 1.5 mm diam.; distal scales becoming progressively longer and relatively narrower; apical scale obovate, 12 × 8 mm, leafy, not keeled, pubescent along midrib. Stipules early caducous, in pairs, free, auriculate at base, the auricle suborbicular, up to 0.2 mm long, with 2–6 acute triangular lobes, glabrous on both surfaces but margins ciliate; upper part of stipule narrowly lanceolate, 8–17 × 1.5–2 mm; outer surface densely pubescent along the midrib, veins sparsely pubescent, margins ciliate, inner surface glabrous, apex acute. Leaves alternate, paripinnate, 4.5–8.5 × 1.6–2 cm; petiole 1–2 mm; leaf rachis 4–8 cm long (up to 12 cm in saplings), moderately pubescent, with a tuft of longer hairs at the insertion of leaflets; leaflets sessile, in 21–27 pairs, upper and middle pairs opposite, lower 3–5 pairs subopposite, 8–14 mm × 2–3 mm (up to 22 × 6 mm in saplings), narrowly oblong, base asymmetric, proximal margin tapering towards the apex, glabrous above, lower surface appearing glabrous with a hand lens but moderately appressed puberulous under a microscope, fringing hairs 0.5–0.75 mm long, present particularly on the lower margins on young leaflets but scattered or absent on mature foliage, midvein central, prominent above and below for most of its length, becoming obscure just before the apex; small glands 1–2 (– 3), not visible with a hand lens but visible under a microscope, present on the distal half of the lower surface, positioned about midway between midvein and margin, always present on basal pair, present or absent on middle pairs, not seen on uppermost pair. Inflorescence a 7–15 - flowered raceme, axis 2.3–3.5 cm long, with a moderate to dense indumentum of golden patent hairs, ca 0.6–1.5 mm long, floral bracts slightly spathulate, 6–10 × 1–3 mm, outer surface densely appressed tomentose, inner surface glabrous, persistent; pedicels with moderately spreading hairs 0.3–0.5 mm long, portion of pedicel below bracteoles 2–4 mm long, bracteoles subopposite to opposite, narrowly oblong, ca 5 × 1.2–1.5 mm, tapering towards the apex in upper third, mostly glabrous but with margins ciliate at least in the lower half and along the basal part of the midvein, with a tuft of hairs at the apex, portion of pedicels above bracteoles ca 2 mm. Hypanthium narrowly campanulate, 1–1.5 mm deep, puberulous at the mouth, otherwise glabrous on both surfaces. Sepals 4, obovate, white, subequal, cucullate, 5–7 × 2.5–3 mm, glabrous on both surfaces except for scattered marginal pubescence on upper third with tuft of hairs 0.2– 0. 3 mm long at the rounded apex. Petals absent. Stamens 10; filaments free, 7–9 mm long, glabrous; anthers elliptic, ca 1.2 mm long. Ovary oblong, 2.3–2.7 × 1.1–1.5 mm, densely golden to red-brown tomentose, on a glabrous stipe 1.5–2 mm long, fused with the hypanthium near its apex, free part of stipe very short; ovules 2; style ca 3–4 mm long, moderately to densely pubescent for most of its length, becoming glabrous just under the stigma, stigma capitate. Pod obovate-triangular, 4.5–6.7 × 2–2.5 cm, upper suture slightly broadened, surfaces and suture moderately golden puberulous. Seeds discoid, 1–2 per fruit, 9–10 × 9–10 × 2–3 mm.

Distribution and chorology.

Talbotiella bakossiensis is currently known only from the Southwest and Littoral Regions in Cameroon (Fig. 1 ). Lower Guinea Domain of the Guineo-Congolian Region.

Habitat.

T. bakossiensis occurs in lowland to submontane forest at 100–1350 m altitude.

Phenology.

Flowering specimens were collected in February, October, and November, and fruiting specimens in February and December.

Preliminary IUCN conservation assessment.

Talbotiella bakossiensis is assessed as Endangered B 1 ab (i, ii, iii, v) + 2 ab (i, ii, iii, v) on the IUCN Red List ( Cheek et al. 2022). Nevertheless, this published assessment does not take into account five collections recently named as this species. The main threats mentioned by the published assessment include shifting agriculture and logging. Including the five recently named collections, the extent of occurrence is now calculated at 2580 km 2 and the estimated area of occupancy as 32 km 2, on the basis of a 2 × 2 km grid size. We believe the threats mentioned by the original assessment are still applicable, and the total of estimated locations reaches five when including the five collections recently named as this species. As a consequence, the assessment of T. bakossiensis remains Endangered B 1 ab (i, ii, iii, v) + 2 ab (i, ii, iii, v).

Additional material.

CAMEROON – Littoral Region • Along the road from Djoukou to Yabassi , 3 km on a side road to Yingui; 4°19’26.3”N, 10°04’18.5”E; 100 m; 10 Oct. 2015; van der Burgt 1889; B, BM, BR [ BR 0000015256874 V] n. v., C n. v., E n. v., EA n. v., ETH n. v., F n. v., FI n. v., FHO n. v., G n. v., GH n. v., H n. v., HBG n. v., K, LBV n. v., LE n. v., LISC n. v., MA n. v., MO n. v., MPU n. v., NY n. v., O n. v., P n. v., PRE n. v., S n. v., SCA n. v., SING n. v., US n. v., W n. v., WAG n. v., YA n. v . • Along the road from Djoukou to Yabassi , 3 km on a side road to Yingui; 4°19’26.3”N, 10°04’18.5”E; 100 m; same tree; 2 Dec. 2019; van der Burgt 2356; B n. v., BR n. v., G n. v., K, LISC n. v., MO n. v., P n. v., WAG n. v., YA n. v. – Southwest Region • Kupe-Mwanenguba, Nyale ; 5°00’N, 9°38’E; 18 Nov. 1998; Cheek 9678; K n. v., WAG n. v., YA n. v . • Kupe-Mwanenguba, Ngomboku, Abang road and then right to forest ; 4°55’N, 9°44’E; 11 Dec. 1999; Cheek 10326; K n. v., YA n. v . • Kupe-Mwanenguba, Ngomboku, forest ridge S of Abang track ; 4°55’N, 9°44’E; 15 Dec. 1999; Cheek 10382; K n. v., YA n. v . • 35 km NNW Kumba, 2 km SW Dikome Balue, Rumpi Mts, Mt Rata ; 4°54’N, 9°14’E; 24 Mar. 1976; Letouzey 14546; BR n. v., HBG n. v., K n. v., P n. v., WAG n. v., YA n. v . • Same data as for preceding; Letouzey 15185; BR n. v., K n. v., P n. v., WAG n. v., YA • Rumpi Hills, near Dikome (Bakume) Balue ; 4°54’N, 9°16’E; Nov. 1991; McKey Rh 2 / 43; K [ K 000093017 ] n. v., WAG n. v . • Rumpi Hills ; 4°50’N, 9°15’E; 1000–1200 m; 7 May 1987; Thomas 7449; K, MO n. v . • Rumpi Hills ; 4°55’N, 9°15’E; 10 Feb. 1995; Thomas 10302; K, WAG n. v., YA n. v . • Rumpi Hills near Madie River ; 4°58’N, 9°15’E; 22 Feb. 1995; Thomas 10443; BR n. v., K, MO n. v., P n. v., WAG n. v., YA n. v .

Notes.

Talbotiella bakossiensis resembles Hymenostegia neoaubrevillei J. Léonard , a species endemic to Gabon. The most important morphological difference is that petals are absent in T. bakossiensis , while there are 2 petals in H. neoaubrevillei . However, the Flore du Gabon ( Aubréville 1968) described the petals of H. neoaubrevillei as “ petals 2, sometimes very reduced or even none at all ”. Many of the collections of T. bakossiensis , including the holotype, have not been seen by us (see Introduction). Our study of the available material reveals several additional differences between the two species. Talbotiella bakossiensis has the leaf rachis slightly winged, with flattened, patent margins; the lower leaflets are alternate or subopposite and the bud scales pubescent outside. Hymenostegia neoaubrevillei has the leaf rachis canaliculate with margins erect, the leaflets opposite and the bud scales mostly glabrous, pubescent only at the base.

Figures

Figure 1. Distribution of Talbotiella couteronii and T. bakossiensis in Cameroon.