Monanthotaxis letestui Pellegr.

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 : 173

43. Monanthotaxis letestui Pellegr. — Fig. 20 ; Map 28

Monanthotaxis letestui Pellegr.(1950) 75. — Lectotype (designated by Le Thomas 1969:259): G.M.P.C. Le Testu 7845 (lecto consisting of 2 sheets: P00362620 , P00362622 ; iso BM000547354 , BM000547355 , BR0000008801678 , BR0000008802347 , P00734029 , P00734030 ), Gabon, Ogooué-Lolo, région de Lastoursville, 8 Jan. 1930.

Popowia hallei Le Thomas (1965) 443, syn. nov. — Monanthotaxis letestui Pellegr. var. hallei (Le Thomas) Le Thomas (1969) 259. — Type: N. Hallé 3508 (holo P00362619), Gabon, Ogooué-Ivindo, Bélinga, 14 Dec. 1964.

Scandent shrub or liana, 1.5–5 m long; young branches densely covered with appressed to ascending, reddish brown hairs c. 0.2 mm long; old branches dark brown to blackish. Leaves: petiole 2–5 mm long, 0.7–1 mm diam, grooved, indument as on branches; lamina elliptic to slightly obovate, 4–12.4 by 1.8–5.2 cm, 1.9–3 times longer than wide, chartaceous, sometimes punctate, discolorous, glossy green and glabrous above, dull and glaucous green below, primary vein dark brown below, above densely covered with yellowish to brownish hairs, below densely covered with erect, pale yellowish hairs 0.2–0.4 mm long, base subcordate to slightly truncate with thickened margin, apex emarginate, rounded to acute, primary vein above impressed, secondary veins 6 –11 per side, straight, curving upwards, tertiary venation percurrent, not visible above. Inflorescences mostly supra-axillary, originating 1–4(–7) mm above axil, lax, pending, 1–4-flowered rhipidia to 12.5 cm long; sympodial rachis 2.4–6(–12) cm long, sparsely covered with appressed hairs; pedicels 1.5–3.9 cm long, 0.3–0.4 mm diam, fruiting pedicels 3.5–5.5(–11.6) cm long, sparsely covered with hairs; lower bracts absent; upper bract halfway or in upper half of pedicel, lanceolate 1–2 by 0.3–0.5 mm, densely covered with reddish brown hairs; flower buds ovoid. Flowers bisexual; sepals slightly connate, depressed ovate, 0.8–1.3 by 1.7–1.8 mm, apex rounded to slightly acute, densely covered with appressed hairs; receptacle c. 1.5 mm diam, flat; petals cream, yellow-green or yellow-violet, 6, in one whorl, narrowly ovate to lanceolate, 3–6 by 1–3 mm outside covered with appressed, reddish brown, short hairs, inside papillate; stamens 12–14, in one whorl, free, obconical, 1–1.3 mm long, filaments 0.4–0.7 mm long, thecae extrorse, connective truncate, with short triangular prolongation pointing outward, papillate, staminodes absent; carpels 8–16, narrowly ellipsoid, 1.1–1.4 by 0.4–0.6 mm, densely covered with reddish brown hairs, ovules 2–4, lateral, stigma ellipsoid to cup-shaped, 0.2–0.3 mm long, grooved, glabrous. Monocarps at least up to 6, yellow to red, ellipsoid to subcylindric, 14– 47 by 6 –7 mm, slightly to strongly constricted between the seeds, slightly rugulose with appressed reddish brown hairs, apex apiculate, apiculum c. 1 mm long, stipes 4–10 mm long, terete. Seeds 1–4, ellipsoid, 8.5–9.5 by 4.5–5.5 mm, tawny-brown, seed ends rounded, raphe visible on both sides.

Distribution — Gabon (Haut-Ogooué, Ogooué-Ivindo, Ogooué-Lolo, Woleu-Ntem).

Habitat & Ecology — In forests with shallow rocky soil. Altitude: 460–1025 m. Flowering: January, February, May, July, September, October, December; fruiting: March, May to July, September, November, December.

Preliminary IUCN conservation status — Vulnerable (VU): B2ab(iii). EOO: 58 689 km 2, AOO: 36 km 2. This species is known from seven populations of which two fall inside National Parks, but the other five are in unprotected areas and under threat of habitat degradation and deforestation.

Notes — 1. Monanthotaxis letestui is easily recognised by the supra-axillary, lax and pending rhipidia. This character is only shared with the allopatric M. oligandra . It can be distinguished from that species by the number of stamen (12–14 vs 6) and the more densely hairy lower leafside.

2. Le Thomas (1969) distinguished 2 different subspecies based on filament length, presence or absence of a style, and impressions or not from the stamens in the petals. However, we found all intermediate forms, including those from the same locality. Therefore, subspecific taxa within M. letestui should not be recognized.

3. J.J.F.E. De Wilde 11213 and 11391 from the coastal forest on sand near Gamba in Gabon are possibly a different (sub) species. The leaves and stems are less densely hairy and the sympodial rachis above the bract is <5 mm long, while in most collections of M. letestui it is> 10 mm long. However, the flowers are indistinguishable from M. letestui and therefore these specimens are tentatively identified as M. letestui .

4. G.H.J. Cusset 1311 from the Republic of the Congo has very elongated seeds, measuring c. 26 by 6 mm. The supra-axillary inflorescence and leaves suggest it probably belongs to M. letestui .

5. The epithet of M. le­testui has been corrected to letestui according to ICBN article 60.11 ( Turland et al. 2018).

Figures

Map 28 Distribution of Monanthotaxis letestui Pellegr. (●, O means uncertain dets or aberrant specimens) and M. mcphersonii P.H.Hoekstra (■).

Fig. 20 Monanthotaxis letestui Pellegr. a. Flowering branch; b. leaf base abaxially; c. flower bud seen from below; d–e. flower bud seen from above; f. flower with one sepal and one petal removed; g. petal, side view; h. petal, inside view; i. arrangement of stamens and carpels seen from above; j. stamen, seen from above; k. stamen,inside view; l. stamen, side view;m. stamen, outside view; n. carpel; o. longitudinal section of carpel; p. fruiting branch; q. seed; r. transverse section of fruit (a–b, f–h, j–l, o: Hallé 3508; c–e, i, m–n, p–r: living specimen Hallé). — Modified from Le Thomas (1969) plate 46.