Monanthotaxis wieringae P.H.Hoekstra, 2021

Hoekstra, P. H., Wieringa, J. J., Maas, P. J. M. & Chatrou, L. W., 2021, Revision of the African species of Monanthotaxis (Annonaceae), Blumea 66 (2), pp. 107-221 : 210-213

78. Monanthotaxis wieringae P.H.Hoekstra , sp. nov. — Fig. 34 ; Map 45

Monanthotaxis wieringae belongs to the group of species with unisexual flowers ( Fig. 1 , clade I). It can be distinguished from most species in having 36 stamens in three or four whorls. It differs from M. letouzeyi in the appressed, yellowish,short hairs on the young branches,which are erect,reddish brown, and longer in M. letouzeyi . It differs from M. mortehanii and M. glomerulata , of which no staminate flowers are known, in having a cuneate leaf base and long and slender petioles. — Type: J.J. Wieringa 3833 (holo consisting of 3 sheets:WAG0151260,WAG0151261,WAG0151262;iso LBV0000658,MO), Gabon, Ogooué-Ivindo, road Mékambo to Makokou, 480 m, 2 Jan. 2001.

Etymology. Monanthotaxis wieringae is named after Jan J. Wieringa, collector of the sole collection of this species. Furthermore,he has collected many species of Monanthotaxis with leaf material on silica gel, which greatly facilitated and improved the molecular analyses of the genus.

Liana, to 30 m long; young branches dark brown, covered with appressed, yellowish hairs c. 0.1 mm long, becoming glabrous; old branches dark brown. Leaves: petiole 6–9 mm long, 0.9–1.3 mm diam, grooved, indument as on branches; lamina elliptic to obovate or narrowly so, 8–13.5 by 3.4–6 cm, 2 or 3 times longer than wide, chartaceous, not punctate, discolorous, medium-green above, grey-green below, above sparsely covered with appressed, yellowish, short hairs, becoming glabrous, primary vein with a more dense and persistent indument, below sparsely covered with appressed, yellow hairs 0.1–0.3 mm long, base cuneate, with thickened black margin, apex acute, secondary veins 10 or 11 per side, straight to curving upwards, tertiary venation percurrent. Flowers unisexual. ♂ Inflorescences leaf-opposed or ramiflorous, composed of solitary flowers to 4-flowered fascicles; sympodial rachis 6–8 mm long, covered with appressed, short hairs; flowering pedicels 6–8 mm long, c. 0.8 mm diam, indument as on rachis; lower bracts ovate, 0.6–0.8 by c. 0.5 mm, indument as on rachis; upper bracts halfway or in lower half of the pedicel, shape, size and indument as lower bracts; flower buds globose; sepals free to slightly connate, depressed ovate, 1.4–1.5 by 1.8–1.9 mm, densely covered with appressed hairs; receptacle c. 2.3 mm diam, convex; petals colour in vivo unknown, 6, in two whorls, outer petals depressed ovate, c. 2.5 by 3.5–3.8 mm, outside densely covered with appressed, brownish, short hairs, inside covered with yellowish, very short hairs; inner petals broadly ovate, c. 1.2 by 1.4 mm, outside and inside covered with yellowish, very short hairs; stamens 36, in three or four whorls, free, oblong to obconical, 0.7–0.9 mm long, filaments c. 0.1 mm long, thecae extrorse, connective truncate, prolongation hiding thecae, densely covered with yellowish hairs, staminodes absent. ♀ Inflorescences cauliflorous, a glomerule or condensed many-flowered panicle; sympodial rachis 1–3.5 cm long, densely covered with appressed hairs; flowering pedicels 10–30 mm long, 0.7–1.1 mm diam, indument as on rachis; lower bracts ovate, 1.3–1.4 by c. 1 mm, indument as on rachis; upper bracts halfway or in upper half of pedicel, shape, size and indument as lower bracts, flower buds ovoid; sepals free to slightly connate at base, broadly ovate, 2–2.4 by 2–2.3 mm, outside densely covered with appressed, brown hairs, inside only hairy at the apex; receptacle c. 2 mm diam, convex; petals green with pale brownish silvery hairs, 6, in two whorls, outer petals, broadly ovate, c. 5 by 4.5 mm, outside densely covered with appressed, pale brownish hairs, inside covered with yellowish hairs c. 0.05 mm long, inner petals elliptic, 2.2–2.4 by 1.4–1.5, outside and inside densely covered with yellowish hairs c. 0.05 mm long; carpels c. 129, narrowly ellipsoid to subcylindric, 1.4–1.5 by 0.3–0.4 mm, densely hairy, ovules 3 or 4, lateral, stigma elongate, 0.6–0.7 mm long, grooved, glabrous. Monocarps and seeds not seen.

Distribution — Gabon (Ogooué-Ivindo).

Habitat & Ecology — In secondary forest.Altitude: c. 480 m. Flowering: January.

Preliminary IUCN conservation status — Critically Endanger- ed (CR): B2ab(iii).AOO: 4 km 2. Only known from one, relatively recent collection from an unprotected area.

Figures

Fig. 34 Monanthotaxis wieringae P.H.Hoekstra. a. Branch with staminate inflorescences; b. inflorescence with pistillate flowers; c. pistillate flower with two outer petals removed; d. staminate flower with two outer petals and one inner petal removed; e. stamen, side view; f. stamen, outside view (Wieringa 3833, WAG). — Drawing by E. Wnkel.

Fig. 1 Bayesian 50 % majority rule consensus tree of the genus Monanthotaxis. Asterisks at nodes indicate node support, i.e., *** Strong node support, ** moderate node support, * weak node support, see Hoekstra et al. (2018). The letters A to K with adjacent black bars indicate the clades. The triangles, circles and squares represent morphological characters of the species which are of some use to distinguis the clades. Green triangles = staminodes absent, red triangles = staminodes present. Green circles = petals in one whorl, red circles = petals in two whorls, yellow circles = petals in bud basally in one whorl, at the top outer petals overlapping the inner ones. Green squares = inflorescences extra-axillary or if cauliflorous also extra-axillary inflorescences present, red squares = inflorescences axillary, supra-axillary or cauliflorous, red and green squares = both extra-axillary and axillary inflorescences present.