Sabicea jongkindii Zemagho, O. Lachenaud & Sonké, 2018

Zemagho, Lise, Lachenaud, Olivier & Sonké, Bonaventure, 2018, Four new species of Sabicea (Rubiaceae) from tropical Africa, with additional notes on the genus, Candollea 73 (2), pp. 277-293 : 286-288

Sabicea jongkindii Zemagho, O. Lachenaud & Sonké , spec. nova ( Fig. 3C–D , 6 ).

Holotypus: LIBERIA. Sino: c. 50 km E of Greenville, 5°05'00"N 8°31'45'W, 14.III.2014, fl. & fr., Jongkind et al. 12457 ( BR!; isotype: K!, MO!, P!, WAG!).

Corolla rubra, stipulis minutis 1‒2 mm longis, inflorescentiis axillaribus 1‒2-floris saepe fasciculatis bracteis bracteolisque parvulis Sabicea bracteolatae Wernham et S. roseae Hoyle affinis , sed differt a primo corollae tubo 16‒18 mm longo (nec 11‒13 mm) et stipulis semper erectis (nec saepe recurvatis), a secundo fructibus late ellipsoideis in sicco 8‒16 × 6‒12 mm (nec oblongis vel fusiformibus (6‒)8‒18 × 3‒6 mm). Ab ambabus calycis lobis linearibus 5‒11 × 0.2‒0.5 mm (nec triangularibus 1.5‒5.5 × 0.8‒1.8 mm) distinguitur.

Scrambling woody liana; young stems ± angular, 1‒3 mm thick, with dense appressed hairs 0.3‒0.7 mm long. Stipules interpetiolar, triangular, 1 ‒2 × 1.8 ‒2.8 mm, acute or shortly bifid at apex, erect, shortly appressed-hairy ouside, persistent. Leaves opposite, usually ± unequal; petiole 0.5‒3.2 cm long, with same indumentum as the stems; leaf-blade elliptic to obovate, 2.7‒8.7 × 1.6‒4.5 cm, cuneate at base, acuminate at apex, ± coriaceous, green on both sides but markedly paler below, drying brownish; upper surface with short and very sparse appressed hairs c. 0.1 mm long, lower surface with similar indumentum, mixed with longer appressed hairs c. 0.7 mm long on the main veins; secondary veins 7‒12 pairs, strongly curved and ascending; tertiary veins darker and conspicuous on the lower leaf surface, forming a very dense reticulum with areolae c. 0.5 mm in diameter. Inflorescences axillary, opposite, 1(‒3)-flowered, often fasciculate (up to 4 per axil); peduncle 0.3‒1 cm long, shortly appressed-pubescent, with a pair of bracts at the apex, and two bracteoles under each flower; bracts ovate, 1.5‒2.5 × 1‒1.5 mm, acute at apex, shortly fused at base (then splitting after anthesis) shortly appressed-pubescent outside, densely villose at the base inside; bracteoles similar but slightly smaller, 1 ‒1.5 × 0.7‒ 1.2 mm. Flowers 5-merous, sessile. Calyx green; tube campanulate, 2‒3.5 × 3‒4 mm, shortly and sparsely appressed-pubescent outside, densely villose inside; lobes linear, 5‒11 × 0.2‒0.5 mm, erect, shortly and sparsely appressed-pubescent on both sides, ± canaliculate inside towards the base, alternating with minute colleters. Corolla red; tube 16‒18 mm long × 2‒2.5 mm wide at base and 4‒5 mm at apex, almost cylindrical, outside with dense appressed silky hairs c. 0.5 mm long, inside sparsely hairy in the upper half and with a ring of dense hairs towards the lower 1/4TH; lobes triangular, 2.5‒3 × 1.7‒2.2 mm, apparently erect, silky-pubescent like the tube outside, minutely papillose inside. Stamens mostly included with only the tips exserted, inserted in the upper part of the tube, sessile; anthers 2.8‒3 × 0.8 mm. Ovary 2‒3 × 2‒2.5 mm, 5-locular, densely covered with short appressed hairs. Disk cylindrical, c. 0.6 mm long, glabrous. Style 5-lobed, included, 12‒14 mm long including the c. 5 mm long linear stigmas, the latter papillose, otherwise glabrous. Fruits red, obovoid to ellipsoid, 8‒16 × 6‒12 mm when dry, sparsely appressed-pubescent, sessile, crowned with persistent calyx. Seeds polygonal, c. 0.5 mm, pale brown, the surface with close parallel striations.

Etymology. – This species is named after Carel Jongkind, collector of the type specimen and specialist of the West African flora, co-author of the reference book Woody Plants of Western African forests (HAWTHORNE & JONGKIND, 2006).

Distribution, ecology and phenology. – Upper Guinea subcentre of endemism (WHITE, 1979). Sabicea jongkindii has a disjunct range ( Fig. 4 ), occurring both in south-eastern Liberia (Sinoe R. basin) and south-western Ghana (Ankasa and surroundings); it may also be expected in Ivory Coast close to the Ghanaian border. The species grows on the edges of lowland wet evergreen forest. The two areas where it occurs are believed to have been forest refuges during dry periods (SOSEF, 1994) and similar disjunct distributions are not uncommon among wet forest species, e.g. Ixora badwinii ( Rubiaceae : DE BLOCK, 1998), Monocyclanthus vignei Keay ( Annonaceae : POORTER et al., 2004) or Synsepalum ntimii W.D. Hawthorne ( Sapotaceae : HAWTHORNE, 2014). Sabicea jongkindii is flowering in November, January and March and is fruiting in March-April and October.

Conservation status. – The extent of occurrence of Sabicea jongkindii is estimated to be 16,937 km ² (within the limit for Vulnerable status under criterion B1) and its area of occupancy to be 20 km ², within the limit for Endangered status under criterion B2. The species occurs in south-eastern Liberia and south-western Ghana, and is known from six specimens representing five extant subpopulations (a sixth one, only known from an old collection around Tarkwa in Ghana, is possibly extinct due to mining activities). Only one of its subpopulations is in a protected area (Ankasa National Park in Ghana); the other ones are exposed to deforestation for agriculture. Even though the species occurs in forest edges, and thus may tolerate a certain degree of habitat degradation, the strong human pressure in its range leads us to anticipate a decline in the extent and quality of habitat, number of locations, number of individuals, and thus AOO and EOO. The five subpopulations represent five “locations” (sensu IUCN, 2012) and the species qualifies as “Endangered” [EN B2ab(i,ii,iii,iv,v)] using the IUCN Red List Categories and Criteria ( IUCN, 2012)

Notes. – This species is very close to S. bracteolata Wernham and S. rosea Hoyle , both of which have similar leaves and inflorescences, a red corolla, and very small stipules that are often bifid at apex. It differs from both species by the linear and usually longer calyx lobes; it is further separated from S. rosea by the relatively broader fruits, and from S. bracteolata by the longer corolla tube and the stipules being always erect ( Table 3 ). The earliest collection of S. jongkindii, Vigne 4841, was briefly discussed under S. bracteolata by HEPPER (1963: 172) who already noted the difference in the calyx lobes.

J.B. Hall in 1972 annotated the type specimen of S. rosea as “probably = S. bracteolata ”, but a careful examination of the material shows them to be distinct species ( Table 3 ). The ranges of S. jongkindii and S. rosea overlap (the latter being much more widespread) but that of S. bracteolata , which is restricted to the highlands of Guinea, appears to be separate from both.

The only flowers seen are short-styled; due to the paucity of the material, it is not known whether the species is heterostylous.

Paratypi. – LIBERIA. Sino: Butaw, 17.III.1948, fr., Baldwin 11486 ( K, MO); Sapo NP , buffer zone , near rapids in Sinoe River , 5°20'06"N 8°48'12"W, 23.XI.2002, fl., Jongkind & Blyden 5349 ( BR, WAG).

GHANA. Western Region: Ankasa Forest Reserve , 6.X.1973, fr., Enti R 1164 ( BR, K, MO, WAG); 2 miles N of Ankasa F.R., 5.IV.1968, fr., Enti & Hall GC 38430 ( FHO, K); near Tarkwa , fl., I.1941, Vigne 4841 ( FHO).

Figures

Fig. 3. – Seeds of Sabicea spp. viewed in electron microscopy. A. Sabicea desseinii Zemagho, O. Lachenaud & Sonké: entire seed; B. Sabicea desseinii: detail of seed surface; C. Sabicea jongkindii Zemagho, O. Lachenaud & Sonké: entire seed; D. Sabicea jongkindii: detail of seed surface. [A–B: J. & A. Raynal 9859, P; C–D: Jongkind et al. 12457, BR] [Photos: I. van der Beeten]

Fig. 6. – Sabicea jongkindii Zemagho, O. Lachenaud & Sonké. A. Flowering stem; B. Node and stipules; C. Node with inflorescences; D. Flower; E. Flower, longitudinal section; F. infructescence with two fruits. [A, C–D:Jongkind & Blyden 5349, WAG; B, E–F: Jongkind et al. 12457, BR] [Drawing: A. Fernandez]

Fig. 4. – Geographic distribution of Sabicea desseinii Zemagho, O. Lachenaud & Sonké (circles), S. ezangae Zemagho, O. Lachenaud & Sonké (squares), S. jongkindii Zemagho, O. Lachenaud & Sonké (triangles) and S. uniflora Zemagho, O. Lachenaud & Sonké (pentagon).