Englerophytum sylverianum Kenfack & 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 : 299-302

Englerophytum sylverianum Kenfack & L. Gaut. , spec. nova ( Fig. 3 , 7 , 8 ).

Typus: C AMEROON. Southwest Region: Korup National Park , descent to Chimpanzee f rom “Big Boulder” , 05˚04’08”N 08˚51’35”E, 120 m, 25.V.1997, fl., Kenfack 764 (holo-: MO!; iso-: K!, WAG!, YA!).

Englerophytum sylverianum Kenfack & L. Gaut. differs from other members of the genus by the combination of a large 5-merous wine red corolla (tube 3.5-4.5 mm, lobes 4.5- 5.5 mm), the stamens with filaments fused into a tube and connate anthers closing the corolla throat, and the large leaves (25-62 X 7-15 cm) with a cuneate base and a silvery underside. It resembles E. libenii , which has much smaller flowers and strongly keeled stipules, and E. paludosum which differs in the pale green corolla, the stamen filaments free or nearly so, and the rounded leaf base.

A small to medium-sized understory tree, up to 10 m high and 25 cm DBH, with white latex; foliage clustered at the apex of the twigs, the latter 6-8 mm in diameter, shortly appressed-pubescent. Stipules paired, lanceolate with in-rolled margins, faintly keeled at base, 10-15 mm long, 2-3 mm wide, soon inrolled and appearing subulate, then caducous, appressedpubescent outside, glabrous inside, persistent or sometimes caducous. Leaves alternate, simple, entire, obovate-elliptic to oblanceolate; petiole 15-45 mm long, 2.5-3.5 mm in diameter, longitudinally ribbed when dry, appressed-pubescent; blade 25-62 cm long, 7-15 cm broad, broadest at 2 / 3 to 3 / 4 of its length, acute at base, narrowly acuminate to apiculate at apex for 5-15 mm, chartaceous and strongly discolorous; upper surface dark green, glabrous; lower surface silvery-white, with a dense immersed whitish indumentum, sometimes with additional scarce 0.5 mm golden to brown medifixed trichomes; primary nerve narrowly canaliculate above, very prominent below and longitudinally ribbed when dry, appressed greyish-pubescent and appearing distinctly golden-brown when fresh; nervation brochidodromous, with 30-40 secondaries 5-10 mm apart, interspersed with parallel inter-secondaries and tertiaries, almost indistinct from each other above, more distinct below, the nerves c. 1 mm apart, clearly raised above, shallowly raised below, forming an angle of 60-70° with the primary nerve, then finally curving and anastomosing 1-1.5 mm from margin. Inflorescences borne on the trunk at 0.5-5 m high, or on the thicker branches below the leaves, fasciculate, with 15-40 densely crowded pendulous flowers; pedicels brown, 20-30 mm long and 1 mm diameter at anthesis, slightly thicker but not accrescent in fruit, appressed -pubescent. Calyx golden-brown, consisting of 5 thick imbricate, transversally wrinkled and widely ovate sepals, 4.5- 5.5 mm long X 3.5-4.5 mm broad, connate at base for c. 2 / 5 of their length, rounded at apex, appressed-pubescent outside (except for a 0.5 mm glabrous and somewhat hyaline margin, fringed with 0.5 mm trichomes, sometimes only visible on the inner three sepals), glabrous inside. Corolla dark wine red with yellowish apex, glabrous; tube 3.5-4.5 mm long, 2.5 mm broad, cylindrical to slightly urceolate; lobes 5, obovate, entire imbricate and erect, 4.5-5.5 mm long X 3.5-4 mm broad, with acute apex. Stamens 5, opposite the corolla lobes; filaments connate, forming a white fleshy tube 2.5-3 mm long in continuation of the corolla tube as seen from inside, i.e. 4-5 mm from the base of the corolla; anthers whitish, coherent with their tips and closing the corolla throat, sagittate, 3 mm long X 1.2 mm broad, extrorse and dehiscing longitudinally, with a 0.5 mm sterile tip. Ovary ovoid, 1.5-2.5 mm, with 5 locules and one ovule per locule, densely hirsute with 1.5 mm long trichomes directed upwards; style conical, glabrous, 3-4 mm long, 0.6 mm in diameter at the base. Fruits fleshy, wine red to bright red when mature, globose to ovoid, 30-40 X 20-35 mm when dry, smooth, glabrous or with remains of a caducous golden-brown pubescence, single-seeded; seed ellipsoid, 25-35 X 14-18 X 10 mm, with a shiny dark brown testa and a broad basiventral scar for 4 / 5 of the length of the seed and 2 / 3 of its breadth, i.e. covering c. 50 % of the seed surface. Embryo with plano-convex 20 X 10 X 4 mm cotyledons, radicle not exserted.

Etymology. – The epithet has been chosen in honour of David Kenfack’s wife, Sylveriste Nkenfack Ngueguim, in recognition of her support during fieldwork that led to the discovery of this new species in Korup.

Distribution and ecology. – Englerophytum sylverianum is known with certainty only from southwest Cameroon and Bioko, but very probably occurs in continental Equatorial Guinea ( Rio Muni) and northern Gabon (Crystal mountains); see notes below. It grows in primary and secondary rainforests on drained soils, from sea level to 1000 m elevation.

In Korup National Park, the population of E. sylverianum seems to be increasing in size. One of us (DK) monitored a population of 652 individuals (with dbh ≥ 1cm) of this species within a 50-ha plot. During a 10 years period, 38 individuals (6 %) died, 64 (9.8 %) recruited, which resulted in a net increase in the population of 26 individuals.

Conservation status. – Englerophytum sylverianum is known from seven locations representing 10 subpopulations. The new species has a restricted range with an EOO estimated to be c. 9,140 km ² (but this figure is not relevant here, as it includes much of the ocean between Cameroon and Bioko) and an AOO of 44 km ². Given the deforestation currently taking place in the Southwest Region in Cameroon, the population reduction is likely to be in excess of 30 % over 3 generations, and a decline in the EOO, AOO, habitat extent and quality, number of subpopulations and number of individuals is expected. The new species is preliminarily assessed here as “Vulnerable” [VU A2c+3c; B2ab(i,ii,iii,iv,v)] according to IUCN (2012).

Notes. – Several sterile collections from Gabon and Equatorial Guinea ( Equatorial Guinea: Littoral Prov., Sud de Etembue, 1°15’N 9°26’E, 1.VIII.1998, ster., Lejoly & van Asbroeck 46, BRLU. Gabon: forêt des Mts de Cristal , XII.1959, ster., Aubréville G 128 , P [ P00099621 ]; Mts de Cristal, Mt Mbilan , 0°27’21”N 10°15’12”E, 2005, ster., MBG transect 239, BRLU) probably belong to E. sylverianum , which they match very well in vegetative characters. However, confirmation from fertile material would be needed.

The species is called “Mbolokonde” by the Bakweri people of southwest Cameroon (McKey 1). The fruits are reportedly edible by sucking (Manning 1720) and have a very sweet flesh (McKey 1). McKey also reports that “according to villagers, the population flowers and fruits gregariously at 3-5 years intervals”.

Paratypi.– CAMEROON. Southwest Region: Korup National Park , path from Science Camp to the plots, 5°0’42’’N 8°48’23’’E, 110 m, 18.X.2015, old fl., Burgt 1891 ( K, YA); Forested slope in the Bakossi Mountains 1-8 km NNE of Menyum village, 5°01’N 9°38’E, 1000 m, imm. fr., Doumenge 455 ( G; MO; WAG); Trail to Korup National Park , 2 km W of Ekondo Titi-Mundemba Road, 4 km N of bridge over Ilor River, c. 5°00’N 8°30’E, 100 m, 11.11.1985, ster., Gentry & Thomas 52694 ( K; MO); Banyong, between Awong and Banyu , c. 15 km W Mayemen, 5°00’N 9°10’E, 420 m, 3.V.1988, ster., Gentry & Thomas 62499 ( MO); Idenau, Onge River , 4°18’N 8°57’E, 100 m, 9.11.1993, ster., Harris 3766 ( K); Korup National Park , E of “Camp 1” along E-W path from “Camp 1” to temporary camp on the way to the Mana River foot bridge, 5°01’N 8°49’E, 100 m, 9.IV.1987, fl., Manning 1720 ( MO; WAG); Bomana village near Idenau , near base of Mt Cameroon , 5.VIII.1974, galled fl., McKey 1 ( P [2 sheets]); Korup National Park , 5°4’18”N 8°52’6”E, 28.II.2012, ster., IRD Plot 263 ( BRLU); Korup National Park , 5°4’58’’N 8°52’25’’E, 279 m, cross mountain trail, near Chimpanzee Camp, 8.VI.2011, fr., Sainge 2708 ( MO, YA); Korup National Park , 5˚04’08”N 8˚51’35”E, 50-ha plot, 11.V.2010, fr, Sainge & Kenfack 2245 ( MO, YA); banks of river Moriba , northern Rumpi Hills , 4° 58’N, 8° 57’E, 297 m, fr, Sainge 4040 ( MO, YA); Bomana, Onge , 4°15’N 9°01’E, 200 m, 6.X.1993, ster., Tchouto 704 ( K); South Korup Reserve , 4°55’N 8°50’E, 50 m, 6-16.VII.1983, fr., Thomas 2248 ( MO; P [2 sheets]; WAG). EQUATORIAL GUINEA: Bioko Sud, Moaba-Moka Trail; Pt 139-138 , 16.III.2007, fl., Luke et al. 11971 ( EA, K).

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. 7. – Englerophytum sylverianum Kenfack & L. Gaut. A. Leafy twig; B. Detail of the lower surface of the leaf, showing venation; C. Branch apex with leaves removed, showing stipules; D. Inflorescence; E. Flower; F. Flower viewed from above, showing the united stamens; G. Corolla longitudinally sectioned and opened, with ovary; H. Fruit; I. Seed, ventral view. [A-G: Kenfack 764; H-I: Sainge & Kenfack 2245] [Drawing: Alice Tangerini]

Fig. 8. – Field photographs of Englerophytum sylverianum Kenfack & L. Gaut. A. Leaves; B. Fruits; C. Seeds; D. Inflorescence. [Photos: A, C: D. Kenfack B: X. van der Burgt, D: M. Sainge]