Greenwayodendron littorale Lissambou, Dauby & 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 littorale Lissambou, Dauby & Couvreur sp. nov. Fig. 5

Diagnosis.

Greenwayodendron littorale resembles G. oliveri by being small trees and from the shape and size of their leaves. Greenwayodendron littorale is however different, being smaller in size (2-5 m versus 5-10 m for G. oliveri ) and the shape of the stamen connectives being tongue-shaped, obtuse or short versus flattened in G. oliveri .

Type.

GABON. Ogooué-Maritime: Gamba, ca. 2 km on sand-track to Sete Cama, 15 Mar 1994, J.J. Wieringa 2476 (holotype: WAG! [WAG0065156]; Isotypes (BM, BR![BR0000015305985], C, EA, FHO, IAGB, IEC, K![K001595], LBV!, LY, MA, MO, MPU, P![P06900984], PRE, UGDA, U![U0045159; U0045160], US, W, WAG! [WAG0065155; WAG0065154], YA, Z.)

Tree 2-5 m tall, d.b.h. 2-5 cm. Young branches at first sparsely pubescent, later glabrous, trichomes ca. 0.1 mm long; old branches glabrous. Leaves: petiole 1.0-3.1 mm long, 0.8-1.2 mm in diameter, sparsely pubescent, trichomes ca. 0.1 mm long; lamina 4.2-7.8 cm long, 2.0-3.8 cm wide, length: width ratio 1.5-2.3, elliptic, base rounded or cuneate, apex acuminate, aristate or caudate, acumen 5-12 mm long, upper and lower side sparsely pubescent; midrib upper side and lower side densely to sparsely pubescent, trichomes ca. 0.1 mm long; secondary veins 4-6 pairs, upper side glabrous, lower side sparsely pubescent, trichomes 0.1 mm long; tertiary veins irregular, indistinct above. Inflorescence axillary, a 1-4 flowered rhipidium. Floral buds ellipsoid, 5.0-5.5 mm long, 2.5-3.0 mm in diameter, densely pubescent; Flowering pedicel 3.0-3.1 mm long, 0.5-0.6 mm in diameter, densely pubescent when young, becoming pubescent to sparsely pubescent at anthesis, trichomes 0.1 mm long, lower bract in lower haft of pedicel, minute; upper bract apical, just below the calyx, 0.9-1.0 mm in diameter, sparsely pubescent, trichomes 0.2-0.3 mm long. Sepals 1.5-1.9 mm long, 1.9-2.2 mm wide, length: width ratio 0.9 broadly ovate, imbricate, fused at the base, apex acuminate, base truncate, outside densely pubescent, inside sparsely pubescent towards the centre inside, trichomes 0.1-0.2 mm long. Inner and outer petals 11.5-12.5 mm long, 1.6-1.8 mm wide, length: width ratio 0.9, narrowly ovate to narrowly elliptic, apex acuminate, base rounded, outside tomentose, trichomes 0.1-0.2 mm long, inside sparsely pubescent to glabrous, glabrous part to 0.5-1.2 mm long, green maturing pale yellow. Male flowers not observed. Hermaphrodite flowers: stamens 4-5 in a single whorl, appressed, 1.7-2.1 mm long, 0.6-0.9 mm wide, connective tongue-shaped, obtuse, short and little developed; carpels 8-10, 1.9-2.1 mm long, 0.6-0.8 mm wide, length:width ratio 2.8, oblong, densely pubescent; ovules 1, oblong; stigmata ovoid, densely pubescent, trichomes ca. 0.1 mm long. Fruiting pedicel 4.5-6.5 mm long, 1.5-2.0 mm in diameter, sparsely pubescent, trichomes ca. 0.1 mm long; stipes 3-4 mm long and 1-2 mm in diameter, sparsely pubescent; monocarps 1-4, 2.5-4.2 mm in diameter, broadly ellipsoid to globose, sparsely pubescent to glabrous, green turning wine red at maturity; seed 1 per monocarp, 1.5-4.0 mm in diameter, ellipsoid to globose, surface covered by a white tegument.

Phenology.

Flowering and fruiting times are not well known. However, a flowering specimen was collected in March and a fruiting one in September.

Distribution.

Restricted to the southern coastal part of Gabon and northern Republic of Congo, 5-50 m (Fig. 6 ).

Habitat and ecology.

Growing on coastal and periodically inundated forests, on sandy soils.

Vernacular names.

Unknown.

Use.

Unknown.

Preliminary conservation status of IUCN.

Endangered [EN]. The extent of occurrence (EOO) of Greenwayodendron littorale is estimated to be over 4,506 km2 and its minimal area of occupancy (AOO) is estimated to be 24 km2 (within the limits for Endangered status under criterion B2). Greenwayodendron littorale is endemic to western Gabon and the Republic of Congo and develops in the lowland coastal forest where it is a dominant species in the undergrowth. The species is found in protected areas (Loango National Park). It is also known from several unprotected forests subjected to logging and habitat destruction due to human activities. Greenwayodendron littorale is known from eight specimens representing five subpopulations. These 5 subpopulations represent a total of 5 “locations” (sensu IUCN 2012), falling within the limit for Endangered status. We project that the ongoing loss of its habitat will induce a continuous decline in the number of mature individuals. Greenwayodendron littorale is therefore assigned a preliminary status of EN B1 ab(iii,v)+2ab(iii,v).

Notes.

Greenwayodendron littorale was previously confused with G. oliveri from West Africa. Besides their clear allopatric distribution (West versus Central Africa), both species are distinct at the morphological level with G. oliveri being a taller tree (5-10 m versus 2-5 m) with usually longer leaves (up to 15 cm long versus up to 8 cm long). Both species also differ in the shape of the stamen connective, being flattened in G. oliveri and tongue-shaped, obtuse, short and little developed in G. littorale . Finally, genetic studies also confirm the distinct nature of both species (Lissambou et al. in prep.). To date, only hermaphrodite flowers were observed.

Selected specimens examined.

Gabon. Nyanga: 6 km southeast of Mayumba, 3°28.21'S, 10°41.90'E, 20 Nov 2015, Wieringa, J.J. 8490 (LBV, WAG). Ogooué Maritime: Gamba, 2°46'S, 10°20'E, 26 Sep 1968, Breteler, F.J. 5649 (LBV, WAG); Near Nyanga river, S of Gamba, 2°28'S, 10°15'E, 25 Jul 1998, Breteler, F.J. 14481 (WAG); Setté Cama, 2°32'S, 9°46'E, 23 Apr 1997, McPherson, G.D. 16812 (LBV); Gamba. 9.1 km N of Gamba-airport along production road branching from road to Ndogo wharf, 2°44.70'S, 9°59.70'E, 28 Dec 1994, Wild, J.J.F.E. de 11217 (LBV, BRLU).

Republic of Congo. Kouilou: P.C.A. NZAMBI, around N’tiétié, N’Gongo forest road 4 km from N’Tiété, 3°52'S, 11°16'E, 29 Apr 1974, Sita, P. 3698 (P).

Figures

Figure 5. Greenwayodendron littorale. A Flowering branch B Detail of lower leaf surface C Detail of upper leaf surface D Flower E Outside view of basal bract F Inside view of basal bract G Outside view of upper bract H Inside view of upper bract I Inside view of sepal J Outside view of sepal K Inside view of outer petal L Outside view of outer petal M Outside view of inner petal N Inside view of inner petal O Detail of hermaphrodite receptacle showing stamens and carpels, all petals removed P Detail of one carpel Q Longitudinal section of two carpels, showing single ovule R Detail of stamen, outside view S Detail of stamen, inside view T Detail of stamen, inside view U Fruiting branch V Seed, latitudinal view W Longitudinal section of seed showing ruminations A-T Wieringa, J. J. 2476 U-W Breteler, F. J. 5649. Drawing by Hans de Vries.

Figure 6. Distribution of Greenwayodendron littorale.