Monanthotaxis sterilis 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 : 200

67. Monanthotaxis sterilis P.H.Hoekstra , sp. nov. — Fig. 29; Map 39

Monanthotaxis sterilis can be distinguished from all other species of Monanthotaxis by the linear to narrowly elliptic leaves and the secondary veins that are almost perpendicular to the primary vein. — Type: T. L. P. Couvreur 869 (holo WAG.1575982; iso LBV, YA), Gabon, Woleu-Ntem,on road from Mitzic to Lalara ( N2 ), just after the bridge over the Lara , 150 m in forest, 382 m, 15 Nov. 2015. Paratypes : A. Bouquet 1041 ( P), Republic of the Congo, Lékoumou,village de Moutséné, Batéké , piste de Bouba , 20 Jan. 1965 ; A. Bouquet 1782 ( P), Republic of the Congo, Lékoumou, Monts Ndoumou, au niveau du village de Mandili , 11 Oct. 1965 ; T. L. P. Couvreur et al. 628 ( YA), Cameroon, Littoral, Ebo Wildlife Reserve , Djuma permanent camp,on east trail, 1000 m, 15 Feb. 2013 ; T. L. P. Couvreur et al. 713 ( LBV, WAG), Gabon, Haut-Ogooué, Ossélé village, 45 km on road from Franceville to Kessala , 20 Mar. 2015 ; T. L. P. Couvreur et al. 731 ( LBV, WAG), Gabon, Haut-Ogooué, Ossélé village, 45 km on road from Franceville to Kessala , 21 Mar. 2015 ; T. L. P. Couvreur et al. 792 ( IEC not seen, WAG), Republic of the Congo, Kouilou, 30 km on Dolisie-Mvouti road, just behind the telephone antenna, 703 m, 21 Sept. 2015 ; G. H. J. Cusset 892 ( P), Republic of the Congo, Kouilou, environs de Dimonika , au-dessus de la source Paris Sangha , 5 Mar. 1980 ; C. Farron 4470 ( P), Republic of the Congo, Lékoumou,35 kms Est Sibiti, Moussoumou , chantier forestier de M. Fouet , 18 Aug. 1965 ; N. Hallé & Le Thomas 371 ( P), Gabon, Ogooué-Ivindo, 25 km SE de Mekambo , route canton sud, 7 Aug. 1966 ; B. Senterre & Obiang Mbomio 3409 ( BRLU), Equatorial Guinea, Rio Muni, Centro Sur, SE du Parc National de Monte Alén, au S du Rio Laña, près de la Cabaña Ecofac de Misergue , 850 m, 17 July 2002 ; J. J. Wieringa et al. 8406 ( WAG), Gabon, Woleu-Ntem, 17 km SE of Mitzic, forestry chantier St. Germain ( Foreex ), 500 m, 16 Nov. 2015 .

Etymology. This species is called sterilis as there are many collections, but all are sterile despite significant efforts to find fertile material.

Shrub or liana, to 6 m long; young branches densely covered with appressed to ascending, reddish brown hairs 0.2–0.4 mm long, becoming glabrous; old branches blackish brown. Leaves: petiole 2–4 mm long, 0.6–0.8 mm diam, slightly grooved, indument as on branches; lamina linear to narrowly elliptic, 9.1–15.2 by 1.4–2.1 cm, 4.9–7.6 times longer than wide, chartaceous, not punctate, glossy dark green above, dull pale greyish green below, above sparsely covered with appressed, white hairs 0.3–0.4 mm long, soon becoming glabrous, primary vein densely covered with ascending, yellowish hairs, below sparsely covered with appressed, yellowish hairs 0.2–0.3 mm long, base cuneate, with slightly thickened black margin, apex acuminate, acumen 10– 20 mm long, secondary veins 15–20 per side, almost perpendicular with primary vein, straight, but curving halfway, tertiary venation slightly percurrent, hardly visible. Flowers, monocarps and seeds not seen.

Distribution — Cameroon, Equatorial Guinea, Gabon, Republic of the Congo.

Habitat & Ecology — In primary forest, submontane forest and secondary rain forest, on hill sides and on sand soil near stream. Altitude: 382– 850 m.

Preliminary IUCN conservation status — Least concern (LC). EOO: 163 087 km 2, AOO: 44 km 2. This species has only been collected a few times as most collectors do not collect sterile material. However, recent field work has shown that this species is actually quite common in the forests of Gabon and surrounding areas (Thomas Couvreur and Paul Hoekstra pers. observ.).

Note — Although the leaf shape is unique within Monanthotaxis , the DNA-based phylogenetic analysis clearly place this species within Monanthotaxis . Also the lianescent habit with glaucous leaves and eucamptodromous venation clearly place this species within Monanthotaxis .

Figures

Map 39 Distribution of Monanthotaxis quasilanceolata P.H.Hoekstra (■) and M. sterilis P.H.Hoekstra (●).