Uvariodendron fuscum (Benth.) R.E.Fr., Acta Horti Berg. 10: 61 (1930)

Dagallier, Leo-Paul M. J., Mbago, Frank M., Couderc, Marie, Gaudeul, Myriam, Grall, Aurelie, Loup, Caroline, Wieringa, Jan J., Sonke, Bonaventure & Couvreur, Thomas L. P., 2023, Phylogenomic inference of the African tribe Monodoreae (Annonaceae) and taxonomic revision of Dennettia, Uvariodendron and Uvariopsis, PhytoKeys 233, pp. 1-200 : 1

Uvariodendron fuscum (Benth.) R.E.Fr., Acta Horti Berg. 10: 61 (1930)

Figs 4 , 19 , 20 , 21 , 22 , 23

≡ Uvaria fusca Benth., Trans. Linn. Soc. London 23(3): 466 (1862); Uva fusca Kuntze, Revis. Gen. Pl. 1: 8 (1891). Type. Equatorial Guinea - Bioko Sur - G. Mann 308 (holotype: K! (K000198801); isotype: P! (P00362657)); 3°30'N, 8°40'E; alt. 396 m; 1860.

= Uvariodendron mirabile R.E.Fr., Acta Horti Berg. 10: 59 (1930). Type. Cameroon - South-West Region • P.R. Preuss 1378 (lectotype: P! (P00315830), designated by Couvreur et al. (2022), B destroyed), zwischen Victoria und Bimbia; 3°58'58.55"N, 9°15'19.17"E; 15 Mar. 1898.

= Uvaria gigantea Engl.; Uva gigantea Kuntze; Uvariodendron giganteum (Engl.) R.E.Fr.; concerning Uvariodendron fuscum var. giganteum (see details under this variety).

= Uvariodendron magnificum Verdc.; syn. nov. concerning Uvariodendron fuscum var. magnificum (see details under this variety).

Description.

Tree 3-15 m tall, D.B.H. 5-35 cm; young branches with long soft hairs producing a whitish appearance quickly falling off to glabrous, old branches glabrous. Petiole 4-35 mm long, 2-8 mm wide, pilose to glabrous. Leaf lamina 160-750 mm long, 43-225 (250) mm wide, length:width ratio (2.1) 2.5-4, narrowly elliptic to elliptic to narrowly obovate, coriaceous, base acute to cuneate to rounded, apex rounded to acuminate, acumen 1-23 mm long; surface above glabrous, surface below pilose to glabrous when young, glabrous when old; midrib impressed above, raised below, glabrous above, pilose to glabrous below; secondary veins 15-33 pairs, weakly brochidodromous, impressed above, raised below; tertiary veins reticulate. Inflorescences borne on trunk and branches, composed of 1-2 (sub)sessile to pedicellate flowers. Flower pedicel 0-15 mm long, 3-6 mm in diameter, velutinous. Flowers bisexual, buds globose, sessile, 6-15 mm high, 6.5-15 mm in diameter, velutinous. Bracts 1 to 6, upper bract 8-35 mm long, 10-50 mm wide, broadly ovate, clasping the pedicel, enclosing the sepals, pubescent outside, glabrous inside. Sepals 3, 11-55 mm long, 13-43 mm wide, ovate, fused at base over 20-50% of their length, velutinous outside, glabrous inside, brown. Outer petals 3, 20-70 mm long, 17-47 mm wide, length:width ratio 1.1-1.7, elliptic to broadly ovate, velutinous outside, glabrous inside, cream to greenish outside, cream with a dark red streak from base up to 75% of the petal length inside. Inner petals 3, 20-53 mm long, 15-38 mm wide, length:width ratio 1.1-2.1, elliptic to broadly obovate to obovate, puberulent outside, glabrous inside, cream outside, dark red to dark purplish red with cream margins inside. Stamens around 2500, 3.5-5 mm long, 0.1-0.5 mm wide, anthers linear, connective prolongation truncate, pale yellow. Carpels 20 to 160, 4-7 mm long, 0.5-2.2 mm wide, velutinous, free; stigma 1-2 mm long, 0.8-1.1 mm wide, coiled, glabrous to velutinous, covered with an exudate at anthesis. Fruiting pedicel 5-18 mm long, 5-8 mm in diameter, pubescent. Monocarps 6 to 80, 20-60 mm long, 11-32 mm wide, length:width ratio 1.7-2.5, cylindrical, curved, acuminate, puberulent, green to brown; sessile to shortly stipitate, stipe 0-4 mm long, 2-5 mm wide, pubescent to glabrate. Seeds 1-16 per monocarp, biseriate, 14 to 23 mm long, 7-11 mm wide, semicircular, orange-brown.

Distribution.

Element of the Lower Guinean Domain and Congolia Domain of the Guineo-Congolian Region and Zambezian Region: Cameroon, Democratic Republic of the Congo, Gabon, Equatorial Guinea (Bioko Island), Nigeria, Uganda.

Habitat and ecology.

Lowland and submontane to mountain mature or old secondary rain forests. Altitude: 100-1400 m a.s.l.

Phenology.

Flowers collected from January to April. Fruits collected from March to April.

Vernacular names.

Cameroon: ‘Limboto’ in Bakweri (van Andel 3761), 'Obom Ossoé’ in Yaoundé (Biholong 279). Gabon: ‘Inkaca’ in Bakota ( Hallé 3156).

Uses.

The young leaves are boiled and used for soup (Cheek 5145) and the ripe fruits are eaten (van Andel 3761).

Notes.

From now on, the name Ud. fuscum encompasses the synonyms Ud. mirabile , Ud. giganteum and Ud. magnificum . Ud. fuscum consists of a large morphological variation of the leaf and flower size, with var. Uvariodendron fuscum magnificum having the largest dimensions, followed by var. Uvariodendron fuscum giganteum and then the type variety being the smallest (Fig. 4 , Table 4 ). Although this variation seems to form a continuum, we recognize three different morphological groups described as varieties (see notes under the varieties). This species resembles Ud. calophyllum , Ud. connivens and Ud. usambarense in having large elliptic to obovate leaves. It differs from Ud. calophyllum and Ud. connivens in having pilose to glabrous young branches and petioles (vs. tomentose in Ud. calophyllum and completely glabrous in Ud. connivens ). It differs from Ud. connivens in having flower pedicels between 0 and 15 mm long (vs. between 10 and 40 mm long) and in having cream petals with dark red streak within the flower (vs. wine red petals both inside and outside).

Preliminary conservation status.

This species is widespread, distributed from Nigeria to Uganda. A previous assessment listed it as Near Threatened NT ( Cheek and Cable 2000). However, the assessment was made on what is now Ud. fuscum var. fuscum and thus needs to be updated. Here, the EOO is estimated at 755,899 km2 and its AOO at 152 km2. Based solely on AOO value, it would qualify for Endangered EN, but none of the other B2 subcriterion are met. Following IUCN criterion B, it is assigned a preliminary conservation updated status of Least Concern LC.

Figures

Figure 4. Morphological continuum in Uvariodendron fuscum: traits comparison for var. Uvariodendron fuscum fuscum (fusc.), var. Uvariodendron fuscum giganteum (gig.) and var. Uvariodendron fuscum magnificum (mag.). Each point represents a measurement. Vertical bars span the minimum and maximum values of the focal traits. Photos, left: leaf of Couvreur 1046; top right: flower, below view, of Couvreur 1046; below right: flower, top view, of Couvreur 990 (CC BY-NC 4.0 Thomas Couvreur).

Figure 19. Uvariodendron fuscum (Benth.) R. E. Fr. var. fuscum A leaf, lower side B apex of young branch with detail of petiole and leaf base, upper side, inset: detail of sparse pubescence on young branch C trunk with flower bud (top) and flower (bottom) D open flower E young fruit with unripe monocarps, one old petal remaining F flower semi-bottom view, showing bracts and sepals G detail of flower after anthesis, note the falling stamens and pollinator insects, inset: detail of Coleoptera full of pollen grains. A, E, G Couvreur 1046 B, C Couvreur 1029 D, F Couvreur 990. Photos Thomas Couvreur.

Figure 20. Uvariodendron fuscum var. giganteum (R. E. Fr.) Dagallier & Couvreur A young branch with leaves, lower side, inset: detail of midrib, note the long soft hairs producing A whitish appearance B young branch, petiole and base of leaf, upper side, note the absence of hairs (fallen off) C flower, top view D flower, side view showing sepals and bracts E young fruit, top view. A Couvreur 1229 B-D Couvreur 1057. Photos Thomas Couvreur.

Figure 21. Uvariodendron fuscum var. giganteum (R. E. Fr.) Dagallier & Couvreur A leaf B flower bud, side view C flower bud, bracts removed, side view D detail of flower bud, two sepals, one outer and two inner petals removed E outer petal, outer view F inner petal, outer view G stamen H carpels, side view and detail of ovules I longitudinal section of receptacle J floral diagram K fruit, longitudinal sections of monocarps. A-K from Halle 3156 (as Ud. giganteum). Drawings by Helene Lamourdedieu, modified from Le Thomas (1969; pl. 50, p. 279), Publications Scientifiques du Museum national d'Histoire naturelle, Paris.

Figure 22. Uvariodendron fuscum var. magnificum (Verdc.) Dagallier & Couvreur A young branch with leaves and apical bud B leaf, upper side C longitudinal section of flower bud D flower, semi-side view E carpel with carpel wall partially removed to show arrangement of ovules, side view F young fruit, side view G monocarp, side view H seed, side view. A-H from Okodi in Hamilton 696 (as Ud. magnificum). Drawings by Mary Griesrson, modified from Verdcourt (1969; fig. 2, p. 517), Kew Bulletin 1969 Royal Botanic Gardens, Kew.

Figure 23. Distribution map of Uvariodendron fuscum. Shades of grey represent elevation, from white (sea level) to darker grey (higher elevation). The inset shows the extent of the map over Africa.