Monanthotaxis scamnopetala (Exell) P.H.Hoekstra

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 : 193-195

63. Monanthotaxis scamnopetala (Exell) P.H.Hoekstra — Fig. 27 ; Map 38

Monanthotaxis scamnopetala (Exell) P.H.Hoekstra in Guo et al.(2017) 15. — Popowia scamnopetala Exell (1932) 207. — Exellia scamnopetala (Exell) Boutique (1951b) 118. — Type: J. Gossweiler 6884 (holo BM000547053; iso COI, K000198958,LISC000082,LISC000084,LISU), Angola, Cabinda, Buco-Zau-Maiombe, 18 Dec. 1916.

Liana, to 15 m long, to 20 cm diam; young branches dark brown to blackish, sparsely covered with appressed, reddish brown hairs c. 0.2 mm long, becoming glabrous; old branches blackish. Leaves: petiole 4–7 mm long, 1–1.8 mm diam, grooved, indument as on branches; lamina oblong-elliptic to narrowly oblong-elliptic, 5–21 by 2.2–7.6 cm, 1.8–3.4 times longer than wide, chartaceous to subcoriaceous, not punctate, glossy dark green above, glaucous below, above glabrous except for primary vein, below sparsely covered with appressed, yellowish hairs c. 0.2 mm long, becoming glabrous, base cuneate to rounded, with slightly thickened margins, apex acute to slightly acuminate, acumen to 10 mm long, primary vein reddish brown, secondary veins yellowish, 8–13 per side, straight but at end curving upwards, tertiary venation percurrent. Inflorescences axillary, composed of solitary flowers; sympodial rachis 0–3 mm long; pedicels 4.5–15 mm long, 0.7–0.9 mm diam, fruiting pedicels 10–30 mm long, 2–2.5 mm diam, indument as on branches, becoming glabrous; lower bracts triangular to ovate, to 0.5 by 0.5 mm, densely covered with appressed reddish brown hairs; upper bract absent; flower buds depressed globose. Flowers bisexual; sepals free, depressed ovate to triangular, 0.5–1.2 by 1–1.5 mm, apex acute, densely covered with appressed, reddish brown hairs, persistent in fruit or falling off; receptacle c. 1.7 mm diam, flat; petals brownish at the outside, creamy white at the inside (the outer ones), white (the inner ones), 6, in two whorls, outer petals ovate to broadly ovate, 6–9 by 5.5–8 mm, outside covered with appressed yellowish hairs, inside only hairy at the apex, inner petals rhombic and geniculate, 5–6 by 3–3.5 mm, white, outside and apex of the inside sparsely covered with appressed hairs; stamens 14 or 15, in two whorls, in groups of (4 or) 5, free, obconical to obovoid, 1.2–1.8 mm long, filaments 0.2–0.4 mm long, thecae latrorse to slightly extrorse, connective truncate, more or less hiding thecae, glabrous, staminodes absent; carpels 3, oblongoid to obovoid, 2.7–2.8 by 1.4–1.6 mm, densely hairy, ovules in two rows, 12–16, lateral, stigma subsessile, conical, c. 0.3 mm long, glabrous. Monocarps 1–3, green to golden brown in vivo, black in sicco, sessile, globose, 1.7–2.4 by 1.7–2.6 cm, verrucose. Seeds 10–14, half-moon shaped, outside convex, inside flat, 12–19 by 6–11 mm, ochre brown, both ends rounded.

Distribution — Central African Republic, Democratic Republic of the Congo, Gabon, Republic of the Congo, Angola.

Habitat & Ecology — In evergreen forest, gallery forest, semi-deciduous forest, old secondary forest and on rock plateau with shallow soil. Altitude: 350– 900 m. Flowering: February, March, July, October, December; fruiting: February to June, August to November.

Vernacular names — Democratic Republic of the Congo: Moamba Nsinga (Pila name) (L. Toussaint 205), Muamba Nsinga (L. Toussaint 398), Ngiko e Likebe (Turumbu name) (C.M. Evrard 2004).

Preliminary IUCN conservation status — Least concern (LC). EOO: 1 349 342 km 2, AOO: 92 km 2. This species has been collected several times recently, including in nature reserves. Therefore, this species is likely not under threat of extinction.

Notes — 1. Monanthotaxis scamnopetala is together with M. mcphersonii the only species of Monanthotaxis with sessile monocarps and biseriate ovules ( Fig. 1 , clade E). It can easily be distinguished from M. mcphersonii by the appressed, short hairs on the stems and leaves.

2. According to Le Thomas (1969) M. scamnopetala sometimes has a geminate inflorescence.

3. According to Boutique (1951a) and Le Thomas (1969) M. scamnopetala has 15–20 ovules per carpel; however, in the drawings of their respective publications a row of 7 ovules ( Boutique 1951a) and two rows of 6 ovules ( Le Thomas 1969) are visible, which coincides with our observations of 12–16 ovules consisting of two rows of 6–8 ovules.

Figures

Map 38 Distribution of Monanthotaxis pynaertii (De Wild.) P.H.Hoekstra (■) and M. scamnopetala (Exell) P.H.Hoekstra (●, O means uncertain det).

Fig. 27 Monanthotaxis scamnopetala (Exell) P.H.Hoekstra. a. Flowering branch; b. flower bud seen from above and below; c. flower seen from above; d. outer petal, outside and inside view; e. inner petal, inner and outside view; f. flower with petals removed; g. stamen, front and side view; h. carpel, front and side view and longitudinal section of carpel; i. floral diagram; j. fruit; k. longitudinal section of monocarp; l. seed (a–i: N. Hallé & Le Thomas 163; j: Donis 2386; k: Flamigni 6371; l: Evrard 2004). — Modified from Le Thomas (1969) plate 47.

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.