Monanthotaxis paniculata 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 : 185-187

57. Monanthotaxis paniculata P.H.Hoekstra — Fig. 23 ; Plate 5d–f; Map 35

Monanthotaxis paniculata P.H.Hoekstra in Hoekstra et al. (2014) 106. — Type: G. D. McPherson 16123 (holo consisting of 2 sheets: WAG0357246 , WAG0357247 ; iso LBV, MO, P01967243 ), Gabon, Ogooué-Ivindo, north of Koumameyong along SHM lumber roads, N0°25' E11°55', 200 m, 31 Jan. 1993.

Liana to 20 m long; young branches densely covered with appressed, reddish brown hairs c. 0.5 mm long, becoming glabrous; old branches dark brown to blackish. Leaves: petiole 4–8 mm long, 1–1.5 mm diam, grooved, densely covered with appressed hairs; lamina ovate to oblong-lanceolate, 8.5–23.5 by 3.3–6.6 cm, 2–4.2 times longer than wide, chartaceous, older leaves punctate below, glaucous or green below, young leaves above sparsely covered with appressed, white hairs c. 1 mm long, becoming glabrous, below densely covered with appressed yellowish hairs c. 2 mm long, less densely so in older leaves, base cuneate to broadly cuneate, with small thickened black margin, apex acute to acuminate, acumen to 25 mm long, secondary veins 10–16 per side, oblique, curving upwards, impressed above, tertiary venation percurrent to slightly reticulate, slightly raised above, below only visible in older leaves. Inflorescences axillary or terminal, in 5.5–27 cm long many-flowered panicle-like rhipidia; sympodial rachis often multiple times bifurcate or trifurcate, densely covered with reddish brown, short hairs, 1–3 flowers in the axil of each upper bract; flowering pedicels 5–22 mm long, 0.4–0.8 mm diam, indument as on rachis; lower bracts elliptic to lanceolate, 1–8 by 0.5–1.5 mm, same indument as on rachis, upper bract absent; flower buds depressed globose. Flowers bisexual; sepals free to slightly connate at base, depressed ovate, 0.6–1 by 1–1.5 mm, apex acute, outside densely covered with reddish brown hairs, inside glabrous, apex acute; receptacle 2–3.5 mm diam, flat; petals yellowish or dull yellow, 6, in one whorl, ovate, c. 3 by 1.5 mm, ovate, outside and inside covered with appressed, yellowish, short hairs; stamens 6, in one whorl, free, opposite the petals, obconical, c. 0.6 mm long, filaments c. 0.2 mm long, thecae introrse, connective truncate, prolonged, kidney-shaped seen from above, c. 1 mm wide, not hiding thecae, glabrous, staminodes 6, alternating with the stamens, c. 0.4 by 0.5 mm; carpels 14–24, ellipsoid, c. 0.9 by 0.4 mm, densely covered with reddish brown hairs, ovule 1, basal, stigma shape subglobose, c. 0.2 mm long, bifurcate, glabrous. Fruits seen from photographs: Monocarps 1–10, green, ellipsoid, covered with reddish brown hairs, apex rounded. Seeds 1, ellipsoid.

Distribution — Gabon (Estuaire, Ogooué-Ivindo, Ogooué-Lolo), perhaps in Cameroon.

Habitat & Ecology — In forest fringe of a marshy savannah and along lumber roads.Altitude: 0– 500 m. Flowering: January; fruiting: June.

Preliminary IUCN conservation status — Endangered (EN): B2ab(iii). EOO: 15 921 km 2, AOO: 12 km 2. This species has been collected once since its publication in 2014. This third collection was from a new location, but also an area that is under threat of habitat degradation by logging and thus our estimate does not change.

Notes — 1. Monanthotaxis paniculata is the only species of Monanthotaxis with a large panicle-like rhipidium. It strongly resembles M. congoensis , but differs in the inflorescence-type, the depressed globose floral buds, the stamens inserted on a black hexagonal disc and the connective prolongation, that is kidney-shaped when seen from above. Vegetatively, M. paniculata can be distinguished by the yellowish indument of the lower leafside. However, more collections are needed to assess the variability in vegetative characters.

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2. Field photos of T.L.P. Couvreur 1108 were seen, which has fruits. No measurements are included in the description as this specimen was not yet examined by the authors.

3. Two specimens from Cameroon, T. L. P. Couvreur 651 and T. L. P. Couvreur 708, probably belong to this species, but they are sterile, which precludes an identification with certainty .

Figures

Fig. 23 Monanthotaxis paniculata P.H.Hoekstra. a. Flowering branch; b. flower bud; c. flower with three petals removed; d. petal, outside view; e. petal, inside view; f. stamen, inside view; g. stamen, side view; h. stamen, outside view; i. stamen, seen from above; j. staminode; k. carpel; l. leaf adaxially (a–k: G.D. McPherson 16123; l: Reitsma 2870). — Drawing by E. Winkel.