Englerophytum paludosum L. Gaut., Burgt & 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 : 289-292

Englerophytum paludosum L. Gaut., Burgt & O. Lachenaud , spec. nova ( Fig. 1-3 ).

– Englerophytum kennedyi Aubrév. & Pellegr ., Fl. Cameroun 2: 71. 1964 [nom. nud.].

Typus: CAMEROON. Southwest Region: Ndian division, Korup National Park , NW plot near P transect, subplot 39PN, 5°01’N 8°47’E, 100 m, 26.V.2007, fl., van der Burgt 944 (holo-: K [ K000460371 ]!; iso-: BR!, E!, G [ G00418157 ]!, MO!, P!, WAG!, YA!).

Englerophytum paludosum L. Gaut., Burgt & O. Lachenaud differs from other members of the genus by the combination of a 5-merous pale green corolla with patent lobes, the stamens with filaments free to the base or nearly so, the large (14- 35 cm long) oblanceolate or spathulate leaves with the base of the lamina shortly rounded, and the persistent acicular stipules. It resembles E. libenii O. Lachenaud & L. Gaut. , E. sylverianum Kenfack & L. Gaut. and E. stelechanthum K. Krause, but these species have the leaves cuneate at base and the stamens filaments connate into a tube.

A medium-sized tree, up to 20 m high and 54 cm DBH, with brown bark and white latex; bole straight, not buttressed, but sometimes with small aerial roots at base; small red pneumatophores occasionally present around the tree; branching dichotomous, foliage clustered at the apex of the twigs, the latter 5-6 mm diam. (innovations 3 mm diam.), shortly appressedpubescent. Stipules paired, acicular with inrolled margins, 6-14 mm long, 0.8-2 mm wide if flattened, persistent, appressedpubescent outside, glabrous inside. Leaves alternate, simple, entire, oblanceolate or spathulate; petiole 5-15(-30) mm long, 2.5- 3.5 mm in diameter, longitudinally ribbed when dry, appressedpubescent; blade 14-35 cm long, 3.7-10 cm broad, broadest at 3 /4 of its length or higher, gradually narrowed to an obtuse or rounded base, rounded to acuminate at apex (acumen up to 15 mm long), chartaceous to coriaceous, strongly discolorous; upper side green, glabrous; lower side silvery white to coppery, with a dense immersed white indumentum intermingled with additional 0.5 mm golden to brown medifixed trichomes; primary nerve canaliculate above, very prominent below, appressedpubescent; nervation brochidodromous, with 26-60 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, faintly raised above and below, forming an angle of 60-70° with the midrib, then slightly curving upwards, and anastomosing 1 mm from margin. Inflorescences ramiflorous, borne on the branches below the leaves and in the lower axils, fasciculate, with 4-10 flowers, most of them pointing downwards; pedicels golden-brown, 10-17 mm long and c. 0.6 mm in diameter at anthesis, 14-28 mm long and 1-2 mm thick in fruit, appressed-pubescent with medifixed trichomes. Calyx golden-brown, consisting of 5 imbricate, broadly ovate or elliptic sepals, 3-3.5 mm long X 2.5-3.5 mm broad, rounded at apex, appressed-pubescent outside (except for a 0.3 mm glabrous and somewhat hyaline margin, sometimes only visible on the inner three sepals) and fringed with white 0.3 mm trichomes, glabrous inside. Corolla whitish to pale green, glabrous; tube cylindrical to slightly urceolate 1.5-3 mm long X 2-2.5 mm in diameter in its broader part; lobes 5, ovate, entire, imbricate and patent, 3 mm long X 2-2.5 mm broad, obtuse at apex. Stamens 5, opposite the corolla lobes; filaments white, obliquely bent outwards, 1.5-2.5 mm long, 1 mm wide at base and 0.4 mm at apex, 0.6 mm apart from each other, free or very shortly united at base into a rim 0.3 mm long in continuation of the corolla tube; anthers initially whitish but soon turning brown, erect or obliquely bent inwards, free from each other, broadly sagittate, 2 mm long X 1.2-1.7 mm broad, shortly apiculate, extrorse and dehiscing longitudinally. Ovary globular, 2 mm long, with 5 locules and one ovule per locule, densely hirsute with 1 mm long trichomes directed upwards; style pale green, narrowly conical, 1.5-2 mm long, 0.4 mm at base. Fruits ellipsoid to ovoid, 25-28 X 15-19 X 11-18 mm when dry, densely puberulous with golden-brown appressed hairs, 1- or 2-seeded; seeds ellipsoid and slightly compressed, 20-21 X 12-14 X 9-10 mm, with a shiny testa and a broad ovate ventral scar for their whole length, 9-10 mm broad at base and gradually narrowing towards apex; embryo with plano-convex cotyledons, 18 X 10 X 4 mm, radicle not exserted.

Etymology. – The species epithet refers to the swampy habitat of the species.

Distribution and ecology. – Englerophytum paludosum is sparsely distributed from southern Nigeria to central D.R. Congo ( Fig. 3A ). It occurs in swamp forests and periodically inundated forests. According to OL’s field experience in Gabon, the species is uncommon in this country.

In the southern part of Korup National Park only two E. paludosum trees ≥ 50 cm stem diameter have been recorded in the “P transect plots” (Total area 155.75 ha; 3,181 registered trees ≥ 50 cm). Being a medium-sized tree species, they only rarely grow larger than 50 cm stem diameter. Sixteen trees between 10 and 50 cm diameter have been recorded in 56 random located subplots (total area 14 ha; 5,755 registered trees between 10 and 50 cm).

Conservation status. – Englerophytum paludosum has a broad range, is known from more than ten locations, and occurs in swampy habitats, which are usually difficult to access and relatively preserved from deforestation. It is therefore assessed as “Least Concern” according to IUCN Categories and Criteria ( IUCN, 2012).

cm

Notes. – Englerophytum paludosum has the stamen filaments free at the base or nearly so, and would have been described in Zeyherella in the classification of Aubréville (1961, 1964a) and Liben (1989). However, this character shows some variation in Englerophytum paludosum . From the limited flowering specimens available, it appears that the populations from Nigeria and Cameroon (including the type specimen) have the filaments shortly united at base, while those from Gabon and D.R. Congo have the filaments entirely free. They are otherwise so similar in vegetative and corolla characters (compare Fig. 2E and F ), and also in ecology, that we regard them as conspecific.

The leaf size varies considerably in E. paludosum . Most of the collections have rather large leaves, and in the vegetative state are easily confused with E. sylverianum , although the latter species has very different flowers, leaves gradually cuneate at base, caducous stipules, and a different habitat (see Table 1 for differences). The small-leaved collections, e.g. Schoenmaker 138, might be mistaken for E. stelechanthum, which shares acicular persistent stipules. However, E. stelechanthum also has very different flowers with fused filaments, the leaves gradually cuneate at base, and a different habitat, being found on drained soils.

The fruits of E. paludosum are edible and much appreciated in D.R. Congo (Leontovitch 27).

Paratypi. – CAMEROON. Littoral Region: Route forestière SNCB (km 36 vers Ndoksom): env. 25 km S Yabassi, 11.V.1976, ster., Letouzey 14905 ( P [2 sheets]); Transect B Tissongo , Douala-Edea Reserve , 26.VI.1976, ster., Waterman & McKey 887 ( K). Southwest Region: riv. de Mosongosele et de Ndian depuis Mosongosele jusqu’à l’entrée amont de la mangrove , env. 20 km au SW de Mundemba, 13.VI.1976, ster., Letouzey 15176 ( P [2 sheets]). GABON. Prov. Estuaire: Forêt classée de la Mondah , E de la route menant au Cap Estérias, 0°35’10”N 9°21’19”E, 20 m, 1.IV.2007, ster., MBG Transect 480 ( BRLU); c. 20 km N of Libreville, forêt de la Mondah , 0°34’N 9°21’E, 18.II.2003, ster., Sosef et al. 2025 ( WAG); Prov. Moyen-Ogooué: Eguémoué [= Lake Oguémoué ], 20.XI.1953, ster., Guillery 1206 ( P); Eguémoué , 12.XII.1953, ster., Guillery 1221bis ( P); Prov. Ngounié: road from Mandji to Rabi , 18 km W of Mandji, Sentier Botanique , 1°45’S 10°16’E, 14.XI.2011, fl., Maas et al. 10325 ( WAG); Prov. Ogooué-Maritime: Préf. de M’paga, à env. 7 km au N du lac Alombié, au S de la réserve de Wonga Wongué, 0°49’59”S 9°26’09”E, 15.X.2014, ster., Bidault et al. 1728 ( BRLU, LBV, MO); Région du Lac Alombié, ± 9 km au NW de Mpaga, 0°49’59”S 9°26’06”E, 111 m, 19.X.2014, fl. buds, Lachenaud et al. 2010 ( BR, BRLU, G, LBV, MO, P, WAG); Rabi- Kounga, N’Gove 2°18’S 9°48’E, 13.XI.1991, fl. & imm. fr., Schoenmaker 138 ( BR, WAG [2 sheets]); Rabi 32 , N’Gove 1°52’S 9°52’E, 11.XII.1990, old fl., van Nek 495 ( WAG [2 sheets]). D.R. CONGO. Prov. Bas-Congo: Boko-Ngufu, 1.XI.1949, ster., Callens 2141 ( BR); Prov. Equateur: Parc National Monkoto , Percée Yenge-Loile , limite Parc National , 3.VIII.1958, fl., Evrard 4447 ( BR); Wendji , env. de Coquillhatville [= Mbandaka ], V.1930, fl., Lebrun 324 ( BR); Terr. Budjala, 25.VII.1937, fr., Leontovitch 27 ( BR); Terr. Bomboma ( Ngiri ), 27.IV.1938, ster., Leontovitch 68 ( BR, 2 sheets, K). NIGERIA. Akwa Ibom state; Distr. Eket; Western end of the Northern Boundary of Stubbs Creek F. R. about 2 miles from Ibeno , 12.V.1953, ster., Onochie FHI 32913 ( K); Distr. Calabar; Akpan , 4.VII.1952, ster., Ujor FHI 31621 ( K); Edo state: Sapoba, s.d., ster., Kennedy 1962 ( BR, K); Sapoba , s.d., fl., Kennedy 2313 ( K); By side of Jamieson R. at Sapoba , 12.XI.1949, ster., Meikle 528 ( K); Sapoba, Jamieson River Bank , 7.VIII.1947, ster., Onochie FHI 23425, ( K, 2 sheets); Sapoba, Jamieson River , 7.IX.1943, ster., Symington FHI 5693 ( K); State unknown: sine loc., s.d., ster., Kennedy 2278 ( BR, MO).

Figures

Fig. 1. – Englerophytum paludosum L. Gaut., Burgt & O. Lachenaud. A. Twig with leaves and inflorescences; B. Detail of the lower surface of the leaf, showing venation (50 x 21 mm); C. Stipules; D. Flower bud, longitudinal section; E. Corolla in bud stage, longitudinal section; F. Open flower, side view; G. Open flower, viewed from above; H. Fruit; I. Seed, lateral view; J. Seed, ventral view. [A-G: van der Burgt 944, BR, K; H-J: Leontovitch 27, BR] [Drawing: L.T. Smith]

Fig. 2. – Field photographs of Englerophytum paludosum L. Gaut., Burgt & O. Lachenaud. A. Aerial roots at the base of the trunk; B. Leaves; C. Inflorescence; D. Apex of twig showing stipules; E. Flowers, Gabon; F. Flowers, Cameroon. [A, B, D: Lachenaud et al. 2010; C, F: van der Burgt 944; E: Maas et al. 10325] [Photos: B, F: X. van der Burgt, A, C, D: O. Lachenaud, E: P. Maas]

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.