Englerophytum libenii O. Lachenaud & L. Gaut., 2016

Gautier, Laurent, Lachenaud, Olivier, Burgt, Xander van der & Kenfack, David, 2016, Five new species of Englerophytum K. Krause (Sapotaceae) from central Africa, Candollea 71 (2), pp. 287-305 : 296-298

Englerophytum libenii O. Lachenaud & L. Gaut. , spec. nova ( Fig. 3 , 6 ).

Typus: G ABON. Prov. Ngounié: Between Mouila and Yéno , about 40 km on road from Mouila, 1°45’S 11°21’E, ± 400 m, 23.IX.1986, Breteler et al. 8125 (holo-: WAG [ WAG0110462 ]!; iso-: BR!, K [ K001243435 ]!, MA [MA521173]!, MO-4314406 !, WAG [ WAG0110463 ]!).

Englerophytum libenii O. Lachenaud & L. Gaut. differs from other members of the genus by the combination of a small, 5-merous wine red corolla (tube 1.8 mm, lobes 1.7 mm), the stamens with filaments fused into a tube and connate anthers closing the corolla throat, the large leaves (25.5-60 X 7-12.5 cm) with cuneate base, and the strongly keeled stipules. The other large-leaved species of Englerophytum have a larger corolla, and the stipules not or hardly keeled.

A small understory tree, 6-8 m high, 10-30 cm in diameter, dichotomously branched, with latex; foliage clustered at the apex of the twigs, the latter 5-10 mm diam., appressed-pubescent. Stipules paired, narrowly lanceolate with inrolled margins, markedly keeled, 10-15 mm long, 2-2.5 mm wide if flattened, coriaceous, appressed-pubescent outside, glabrous inside, tardily caducous. Leaves alternate, simple, entire, oblanceolate; petiole 20-35 mm long, 2.5-4 mm in diameter, longitudinally ribbed when dry, shortly appressed-pubescent; blade 25.5-60 cm long, 7-12.5 cm broad, broadest at 2 / 3 or 3 / 4 of its length, acute to obtuse at base, rounded at apex or with a short blunt acumen <3 mm long, coriaceous and strongly discolorous; upper side green, glabrous; lower side pale greyish-coppery to silvery, with a dense immersed whitish indumentum intermingled with sparser golden-brown medifixed trichomes; primary nerve in continuity of the petiole, canaliculate above, very prominent below, appressed-pubescent; nervation brochidodromous and densely parallel, with numerous secondaries hardly distinct from inter-secondaries and tertiaries, the nerves c. 1 mm apart, faintly raised on both sides, forming an angle of 60-80° with the primary nerve, then finally curving and anastomosing c. 1 mm from margin. Inflorescences borne on the trunk, and on the branches up to the axils of the lower leaves, fasciculate, with 4-22 flowers apparently pointing downwards; pedicels 12-20 mm long and 0.5-1 mm in diameter at anthesis, becoming slightly thicker but not accrescent in fruit, appressed golden-brown pubescent. Calyx brown, consisting of 5 imbricate and broadly ovate sepals, 2-2.5 mm long X 1.5-2.5 mm broad, obtuse at apex, appressed golden-brown pubescent outside (the inner ones often with a narrow hyaline glabrous area on the margin, fringed with short trichomes), glabrous inside. Corolla wine red, glabrous; tube 1.8 X 1.5 mm, ± cylindrical and constricted towards the apex; lobes 5, broadly ovate, entire, imbricate and erect, c. 1.7 X 1.3 mm, subacute at apex. Stamens 5, opposite the corolla lobes; filaments entirely connate, forming a short cylindrical fleshy tube c. 1 mm long in continuation of the corolla tube when seen from inside; anthers dirty brown, connivent at apex and closing the corolla throat, sagittate, c. 1.5 mm long X 1 mm broad, shortly apiculate, extrorse and dehiscing longitudinally. Ovary piriform, c. 1.5 mm long, with 5 locules and 1 ovule per locule, densely hirsute with stiff trichomes directed upwards; style cylindrical, 1 mm long, glabrous. Fruits fleshy, red when mature, globose to ovoid, 24-30 X 16-35 mm when dry, smooth or slightly lobed (at least when dry), shortly puberulous and eventually glabrescent, 1- to 5-seeded; seeds 17-27 X 12-18 X 12-13 mm, with a shiny testa and a broad ovate ventral scar for their whole length, 8-9 mm broad at base and gradually narrowing towards apex; embryo with plano-convex cotyledons, 14 X 10 X 4 mm, radicle not exserted.

Etymology. – The specific epithet refers to the Belgian botanist Louis Liben (1926-2006) to honour his important contribution to the study of the Central African flora. Liben published one family treatment in the “Flore du Cameroun ” series ( Combretaceae ) and several in the “Flore d’Afrique Centrale” (the most notable being Combretaceae , Oleaceae and Rhizophoraceae ). His work on Sapotaceae for the flora, unfinished for health reasons, was particularly helpful in understanding the taxonomy of Englerophytum and its allies. More information about his life and work can be found in Evrard & Bamps (2006) and Fabri (2007).

Distribution and ecology. – Englerophytum libenii is known from southwest Cameroon and central Gabon; it is likely to be more widespread, but appears to be rare. It occurs in primary and secondary forest on drained soils, up to 400 m in altitude.

Conservation status. – Englerophytum libenii has an extent of occurence (EOO) of 13,200 km ² and an area of occupancy (AOO) of 12 km ² [calculation using Bachman et al. (2011) with a with a grid cell size of 2 X 2 km]. It is known from three locations only, none of which is protected. Forest exploitation and clearance for agriculture represent potential threats, and are likely to result in a decline of the EOO, AOO, extent and quality of habitat, number of subpopulations and number of individuals. The new species is preliminarily assessed here as “Endangered” [EN B2ab(i,ii,ii,iv,v)].

Notes. – In vegetative characters, E. libenii is very similar to E. gigantifolium described above. The flowers, however, are strikingly different, being smaller, and with 5 (instead of 7-8) corolla lobes and stamens, the latter coherent by their tips, and the corolla tube ± cylindrical and constricted at apex. E. libenii also closely resembles E. sylverianum ; the latter also has a 5-merous corolla and an thers coherent by their tips, but its flowers are much larger. The differences between the three species are summarised in Table 1 . The fruiting specimens Champluvier 6101 and 6106 are referred to E. libenii due to the small size of their calyx (smaller than the flowering calyx of E. gigantifolium ). The markedly keeled stipules of E. libenii appear to be diagnostic of the species; they are, however, not always well-preserved on herbarium specimens.

The collections of E. libenii from Cameroon and Gabon are well-separated geographically, but their flowers are very similar and we have not found any significant differences, although the Cameroon material tends to have larger leaves. The specimen Letouzey 14366 ( Cameroon. Southwest Region: Entre Nongomadiba et Supe , 40 km au N de Kumba (feuille IGN 1/200 000 Mamfe ), 21.VIII.1975, fr., (BR, K, P)), which the collector considered conspecific with 14333, probably belongs to this species, but since it consists only of detached fruits, a slight doubt remains.

Paratypi. – CAMEROON. Southwest Region: Près Numba, 45 km ENE Mamfe, 18.VIII.1975, fl. & imm. fr., Letouzey 14333 ( BR, K, P). GABON. Prov. Moyen-Ogooué: Mboumi, 0°18’- 0°30’S 10°45’- 10°48’E, 1.II.2000, fr., Champluvier 6101 ( BR); ibid. loc., 1.II.2000, fr., Champluvier 6106 ( BR).

Figures

Fig. 3. – Distribution maps of the five new species of Englerophytum K. Krause. A. Englerophytum. paludosum L. Gaut., Burgt & O. Lachenaud; B. Englerophytum gigantifolium O. Lachenaud & L. Gaut. (squares) and E. sylverianum Kenfack & L. Gaut. (circles); C. Englerophytum libenii O. Lachenaud & L. Gaut. (squares) and E. ferrugineum L. Gaut. & O. Lachenaud (circles). Open symbols indicate specimens associated with doubt.

Fig. 6. – Englerophytum libenii O. Lachenaud & L. Gaut. A. Leafy twig; B. Portion of twig with stipules and base of petioles; C. Detail of lower surface of the leaf, showing venation; D. Inflorescence; E. Flower, side view; F. Flower, longitudinal section; G. Portion of corolla with stamens, seen from inside; H. Flower, viewed from above; I-J. Fruits (dry condition); K. Seed, ventral view; L. Seed, lateral view. [A-C: Champluvier 6101, BR; D-H: Breteler et al. 8125, BR; I-L: Champluvier 6106, BR] [Drawing: A. Fernandez]