Greenwayodendron gabonicum (Le Thomas) Lissambou & Couvreur, 2018

Lissambou, Brandet-Junior, Hardy, Olivier J., Atteke, Christiane, Stevart, Tariq, Dauby, Gilles, Mbatchi, Bertrand, Sonke, Bonaventure & Couvreur, Thomas L. P., 2018, Taxonomic revision of the African genus Greenwayodendron (Annonaceae), PhytoKeys 114, pp. 55-93 : 55

Greenwayodendron gabonicum (Le Thomas) Lissambou & Couvreur comb. nov. Fig. 1

Polyalthia suaveolens (Engl. & Diels) var. gabonica Pellegr. ex Le Thomas., Muséum National d’Histoire Naturelle. Paris. Vol. 16. 206. (1969) ≡ Greenwayodendron suaveolens var. gabonica (Pellegr., ex Le Thomas) Verdc., Adansonia, sér. 2, 9 (1). (1969).

Type.

GABON. Ogooué-Lolo: Région de Lastoursville, 25 Feb 1930, G.M.P.C. Le Testu 7936 (lectotype, designated by Le Thomas 1965 p. 453, P![P00363322]; isotypes: BM web [BM000547163]; BR![BR880441]; P![P0036331]).

Tree 4-20 m tall, d.b.h. 4-40 cm in diameter. Young branches densely to sparsely pubescent, trichomes 0.5-1.0 mm long; old branches sparsely pubescent. Leaves: petiole 4.0-11.1 mm long, 1.0-3.3 mm in diameter, densely to sparsely pubescent, trichomes 0.4-1.2 mm long, indumenta brown; lamina 10.0-26.3 cm long, 4.0-9.6 cm wide, length:width ratio 1.9-3.6, elliptic to narrowly elliptic, base rounded cuneate, apex acuminate, acute, apiculate or emarginate, acumen 8-35 mm long, upper side densely pubescent, lower side densely pubescent; midrib upper and lower sides densely pubescent, trichomes 0.5-1.2 mm long, indumenta tomentose; secondary veins 6-11 pairs, upper side pubescent, lower side densely pubescent, trichomes 0.3-1.0 mm long; tertiary veins upper side sparsely pubescent, lower side densely pubescent, irregularly prominent or indistinct above. Inflorescence axillary, a 1-4 flowered rhipidium. Floral buds ellipsoid, 6-9 mm long, 2.0-3.2 mm in diameter, densely covered with long trichomes. Flowering pedicel 4.5-6.0 mm long, 2.0-2.2 mm in diameter, densely pubescent, trichomes ca. 0.5 mm long, lower bract in lower haft of pedicel, minute, upper bract apical, just below the calyx, 4.8-5.2 mm in diameter, densely pubescent, trichomes ca. 0.6 mm long. Sepals 3.5-4.1 mm long, 4.5-4.7 mm wide, length:width ratio 0.8-0.9 broadly ovate, imbricate, fused at the base, apex acuminate, base truncate, outside pubescent, inside sparsely pubescent, trichomes 0.1-0.5 mm long. Inner and outer petals 22.7-24.6 mm long, 2.3-3.5 mm wide, length:width ratio 0.8-0.9, narrowly ovate to narrowly elliptic, apex acuminate, base rounded; outside tomentose, trichomes 0.5-0.6 mm long; inside sparsely pubescent to glabrous; glabrous part to 4.2-4.6 mm long from the base; petals green maturing pale yellow. Male flowers: stamens 24-33, in several whorls, 3.2-4.2 mm long, 0.4-0.6 mm wide, tightly appressed; connectives tongue-shaped or lobulated. Hermaphrodite flowers: not observed. Fruiting pedicel 7.0-13.1 mm long, 2.0-3.5 mm in diameter, sparsely pubescent, trichomes ca. 0.5 mm long; stipes 5.5-12.0 mm long, 1.5-3.1 mm in diameter, sparsely pubescent; monocarps 1-8, 11.0-19.5 mm in diameter, broadly ellipsoid to globose, sparsely pubescent to glabrous, green turning wine red at maturity; seeds 1-4 per monocarp, 7.8-15.4 mm in diameter, ellipsoid to globose, hemispherical or flattened, flattened on one side when more than one seed per monocarp, surface covered by a white tegument.

Distribution.

Mainly occurring in Gabon and one collection from the Republic of Congo; 10-500 m (Fig. 2 ).

Habitat and ecology.

In primary and secondary forests, also occurring in forest-savannah mosaics (Lope and Wonga Wongué).

Phenology.

In Gabon, G. gabonicum flowers from January to March, immature fruits May to October and mature fruits November to December (Amman Bush; Personal communication), also based on herbaria.

Vernacular names.

Gabon: Mutunga (Aduma, Awadji, Nzebi), Otunga (Fang, Kota, Obamba).

Preliminary conservation status of IUCN.

Least Concern [LC]. The extent of occurrence (EOO) of Greenwayodendron gabonicum is estimated to be over 106,375.19 km2, whereas its area of occupancy (AOO) is estimated to be 128 km2 (which falls within the limits for Vulnerable status under criterion B2). The species, recorded from Gabon and the Republic of Congo, is now known from at least 35 specimens representing 22 subpopulations. These 22 subpopulations represent 20 different locations (sensu IUCN 2012), many more than 10 locations, which are the upper limit for Vulnerable status under the subcriterion ‘a’. Greenwayodendron gabonicum has been collected in 5 protected areas in Gabon (National Park: Moukalaba-Doudou, Lopé, Ivindo, Waka) and Wonga Wongue Reserve and from unprotected areas. This taxon is relatively low in abundance except in two localities (Wonga Wongue Reserve and Lopé Park) where the relative abundance is high. The main threat to G. gabonicum is its habitat destruction resulting from logging activities, especially in the coastal part of Gabon. Notwithstanding these human activities, with varying levels of impact, the species appears not as threatened as it is an abundant and quite widespread species. The available information suggests that the number of subpopulations and mature individuals of G. gabonicum , as well as its EOO and AOO, will not decrease noticeably in the near future.

Uses.

Unknown.

Notes.

Greenwayodendron gabonicum is easily differentiated from all other species of the genus by its dense tomentose pubescence mainly along the petiole and midrib. In addition, G. gabonicum is the only species to have a densely pubescent or sparsely pubescent upper leaf lamina and has the longest leaves, petals and monocarps of the genus.

This species was initially described as a variety of G. suaveolens . However, phylogeographics ( Dauby et al. 2010), genetic data ( Piñeiro et al. 2017; Lissambou et al. in prep.) and morphological characters (leaf size, pubescent, flower and fruit size) clearly support the hypothesis that this entity represents a distinct species altogether leading us to make this new combination.

Since there were two specimens of Le Testu 7936 in Paris, we chose the specimen barcoded P00363322 as the holotype of G. gabonicum . Specimen P0036331 is thus an isotype.

This species was, until recently, suggested as a strict endemic to Gabon, however it has also been collected in the Republic of Congo (P. Sita 4045) in the Niari region (Fig. 2 ).

Selected specimens examined.

Gabon. Haut-Ogooué: Ossélé village, 45 km on road from Franceville to Kessala, 1°51.28'S, 13°50.80'E, 23 Mar 2015, Couvreur, T.P.L. 746 (WAG, LBV, BRLU). Moyen-Ogooué: Zone de Mabounié, 45 km southwest of Lambaréné, north bank of the Ngounié River, 0°26.706'S, 10°19.458'E, 13 Dec 2012, Bidault, E. 800 (BRLU, LBV, MO); Concession Rougier du Haut-Abanga, southeast of Mikongo, northern part of the Mekie Mountains, 0°24.135'N, 11°13.212'E, 13 Jun 2008 Dauby, G. 909 (BRLU, LBV, MO); ibid. loc., 0°46.3956'S, 10°28.3332'E, 10 May 2012, Dauby, G. 2809 (BRLU, LBV, MO). Ngounié: ibid. loc., 0°28.854'S, 10°18.846'E, 14 Nov 2013, Bidault, E. 1297 (BRLU, LBV, MO); ibid. loc., 0°47.729'S, 10°31.991'E, 8 May 2012, IRD plot 91 (BRLU, LBV, MO). Nyanga: Chantier CEB, ca. 35 km SW of Doussala, 2°30'S, 10°30'E, 18 May 1985, Reitsma, J.M. 1030 (LBV, WAG); Inventory, chantier CEB, ca. 50 km SW of Doussala, 2°36'S, 10°35'E, 19 Oct 1985, Reitsma, J.M. 1679 (LBV). Ogooué Ivindo: Route chantier Doti 3 - Leroy Gabon. Forêt des abeilles, 0°41'S, 11°54'E, 5 Oct 1993, Gesnot 8 (BRLU, LBV, MO); Forêt des abeilles, 0°41'S, 11°54'E, 15 Nov 1993, Gesnot 165 (BRLU, LBV, MO); Station de Recherche de l’Institut de Recherche en Ecologie tropicale (IRET-Ipassa), 0°30.303'N, 12°47.748'E, 18 Dec 2014, Lissambou, B.J. 300 (BRLU, LBV); ibid. loc., 0°28.62'N, 12°46.71'E, 28 Apr 2015, Lissambou, B.J. 1134 (BRLU, LBV); Réserve de la Lopé au sud d’Ayem, chantier Soforga, 0°25'S, 11°30'E, 5 Mar 1989, McPherson, G.D. 13716 (LBV); South of Ayem, western border of Lopé-Okanda Reserve, 0°25'S, 11°30'E, 9 Nov 1991, McPherson, G.D. 15498 (BR, LBV, P, WAG). Ogooué Lolo: Région de Lastoursville, 0°49'S, 12°43'E, 25 Feb 1930, Le Testu, G.M.P.C. 7936 (BR, P). Ogooué Maritime: Région du lac Alombié, +/- 10 km to the north of Mpaga, 0°29.412'S, 9°16.3608'E, Oct 2014, Lachenaud, O.L.S. 1926 (LBV, BRLU); Mpaga. Département de Bendjé, 0°50.005'S, 9°27.771'E, 11 Oct 2014, Lissambou, B.J. 0001 (BR, BRLU, L, LBV, MO, P); ibid. loc., 0°50.030'S, 9°26.175'E, 11 Oct 2014, Lissambou, B.J. 0004 (BR, BRLU, L, LBV, MO, P); Mpaga. Département de Bendjé, SW of Lambaréné, near Lake Ezanga; Conoco drilling site; sandy soil, 1°0.345'S, 10°11.818'E, 13 Feb 1991, McPherson, G.D. 15293 (LBV).

The Republic Congo. Niari: Chaillu, Région de Komono, about Mbaya Mossendjo road, 2°57'S, 12°43'E, 15 Nov 1976, Sita, P. 4045 (BR).

Figures

Figure 1. Greenwayodendron gabonicum. A Flowering branch B Detail of lower leaf surface C Detail of upper leaf surface D-E Detail of leaf apex F Flower G Detail of male receptacle, inner and outer petals removed H Outside view of basal bract I Inside view of basal bract J Outside view of upper bract K Inside view of upper bract L Inside view of sepal M Outside view of sepal N Inside view of outer petal O Outside view of outer petal P Outside view of inner petal Q Inside view of inner petal R Detail of androecium S Detail of inner row of anthers (S 1 Inside view, S 2 Outside view) T Detail of outer row of anthers (T 1 Inside view, T 2 Outside view) U Detail of outer row of anthers, different morphology (U 1 Inside view, U 2 Outside view) V Fruiting branch W Seed, latitudinal view X Longitudinal section of seed showing ruminations. A Le Testu, G. M. P. C. 7936 B-U 2 McPherson, G. 13736 V-X McPherson, G. 15498. Drawing by Hans de Vries.

Figure 2. Distribution of Greenwayodendron gabonicum.