Englerophytum ferrugineum L. Gaut. & O. Lachenaud, 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 : 302-304

Englerophytum ferrugineum L. Gaut. & O. Lachenaud , spec. nova ( Fig. 3 , 9 ).

Typus: GABON. Prov. Estuaire: Mts de Cristal , Route de Kinguélé, 18.I.1968, fl., Hallé & Villiers 4506 bis (holo-: P [ P00099668 ]!).

Englerophytum ferrugineum L. Gaut. & O. Lachenaud differs from other members of the genus by the combination of large oblanceolate leaves (15.5-)23-70 X (4.2-) 6-15 cm with dark ferruginous-brown underside, many-flowered inflorescences borne on the trunk, short flowering pedicels (3-6 mm) and stamens with f ilaments fused into a tube and connivent anthers. The leaf colour and indumentum resembles Zeyherella letestui Aubrév. & Pellegr., but that species has free stamen filaments, inflorescences with few flowers (10-20) on longer pedicels (8-10 mm) and borne on the leafy twigs (not on the trunk), and rather small leaves, not exceeding 17 X 5 cm.

A medium-sized tree, 20 m high and 40 cm DBH, with white latex; twigs 8 mm in diameter, densely appressedpubescent with dark brown indumentum. Stipules paired, falciform with inrolled margins, not keeled, 8-15 mm long X 2-4 mm broad, appressed-pubescent with ferrugineous-brown indumentum outside, glabrous inside, persistent or caducous. Leaves alternate, simple, obovate to oblanceolate; petiole 20- 30 mm long, 5-7 mm in diameter, longitudinally ribbed when dry, with a persistent dense appressed ferrugineous-brown pubescence; blade (15.5-) 23-70 cm long, (4.2-) 6-15 cm broad, broadest at 2/3 of its length, acute to obtuse at base, rounded to shortly acuminate at apex (acumen up to 1 cm), chartaceous and strongly discolorous; upper side green, glabrous except for very scattered 0.4-1.2 mm medifixed trichomes; lower side dark ferruginous-brown, with a dense immersed white indumentum mostly hidden by an additional dense external layer of adpressed ferruginous 0.3-1.0 mm trichomes; primary nerve in continuity of the petiole, canaliculate above, very prominent below, appressed brownish-pubescent; nervation brochidodromous, with 40-00 secondaries c. 10 mm apart, interspersed with parallel inter-secondaries and tertiaries, indistinctly raised above and shallowly raised below, forming an angle of 70-80° with the primary nerve, then finally curving and anastomosing 2 mm from the margin. Inflorescences on the trunk, fasciculate, with 100-200 very densely aggregated flowers; pedicels 3-6 mm long and 0.6 (proximal)-1.0 (distal) mm wide at anthesis, shortly appressed brown-pubescent. Calyx ferrugineous-brown, consisting of 5 sepals shortly united at base, the lobes imbricate, 3 mm long X 3.5 mm broad, obtuse at apex, very shortly appressed pubescent outside (the outer sepals entirely brown-pubescent, the inner ones with golden trichomes and a 0.3 mm glabrous area inside the ciliate margin), glabrous inside. Corolla (colour unknown) glabrous, spherical, 4-5 mm in diameter; tube cupshaped, very short, 0.5-1 mm long; lobes 5, broadly ovate to semi-circular with rounded apex, imbricate, 4 X 4 mm. Stamens 5, opposite the corolla lobes; filaments connate into a cylindrical tube 2.3 mm long, attached to and in continuation of the corolla tube and concealing the ovary; anthers connivent and closing the corolla throat (possibly splitting at a later stage of flower development), broadly sagittate, 3 mm long X 1.5 mm broad, shortly apiculate, extrorse and dehiscing longitudinally. Ovary conical, 1.0 mm high and 1.0 mm diameter at base, with 5 locules and one ovule per locule, densely hirsute with stiff 1.9 mm long trichomes directed upwards; style glabrous, 2 mm long, 0.6 mm in diameter at base, tapering to 0.3 mm at the blunt apex. Fruits unknown.

Etymology. – The specific epthet refers to the ferruginousbrown colour of the lower leaf surface, twigs, pedicels and calyx.

Distribution and Ecology. – Englerophytum ferrugineum is endemic to the Crystal Mountains in north-western Gabon. It grows in primary forest on drained soils, or sometimes along rivers, 500-600 m in altitude.

Conservation status. – Englerophytum ferrugineum is known from three locations, representing an EOO and AOO of respectively 79 and 12 km ², and all situated outside protected areas. The species has a narrow range and deforestation for mining and/or agriculture represents a potential threat. A decline in EOO, AOO, habitat extent and quality, number of subpopulations and number of individuals is expected. It is preliminarily assessed here as “Endangered” [EN B1ab(i,ii,iii,iv,v)+B2ab (i,ii,iii,iv,v)].

Notes. - The type collection of E. ferrugineum (Hallé & Villiers 4506 bis) only consists of inflorescences collected on the trunk of a medium-sized tree 20 m high, whose foliage was probably out of reach of the collectors. The description of the vegetative parts is based on the paratype Hallé & Villiers 4506, collected on the same day by the same collectors in the same locality, on a smaller tree 7 m high. The collectors were confident that the two collections were conspecific, as the label of N° 4506 says: “Fleurs voir 4506 bis”. Since they were experienced botanists and the species has a very distinctive foliage, we have no reason to question this association.

Vegetatively, this species resembles Zeyherella letestui Aubrév. & Pellegr., which has the same dark brown indumentum on the lower side of the leaves. The latter, however, differs in the free stamen filaments, the inflorescences with few flowers (10-20) on longer pedicels (8-10 mm) and borne on the leafy twigs (not on the trunk), and the rather small leaves, not exceeding 17 X 5 cm. The leaves of Englerophytum ferrugineum are much larger, except sometimes at the very apex of the twigs.

A collection from southern Cameroon, Letouzey 9221 (P), and another from Monts de Cristal in Gabon, MBG Transect 1025 (BRLU), have leaves resembling this species, but not so densely dark brown pubescent beneath, and with non-appressed T-shaped hairs. They probably represent an undescribed related species; unfortunately, both collections are sterile.

Paratypi. – GABON. Estuaire. Mts de Cristal, route de Kinguélé , 18.I.1968, ster., Hallé & Villiers 4506 ( P [2 sheets]); Mts de Cristal, Mt Mbilan, 0°28’18”N 10°15’24”E, 2005, ster., MBG Transect 443 ( BRLU); Mts de Cristal, montagnes de Mvé Lakéné , 0°34’0”N 10°11’57”E, 2007, ster., MBG Transect 762 ( BRLU); Mts de Cristal, route en venant à Mela , s.d., ster., Normand 1 ( P).

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. 9. – Englerophytum ferrugineum L. Gaut. & O. Lachenaud. A. Inflorescence; B. Flower bud; C. Longitudinal section of flower; D. Longitudinal section of corolla; E. Leaf blade detail, upper surface; F. Leaf blade detail, lower surface; G. Branch apex showing stipules; H. Extremity of twig with leaves. [Drawing: G.Loza]