Psychotria samoritourei was discovered in the course of a project to map the vegetation and identify plant species of potential conservation concern in the Pic de Fon section of the c. 110 km long, Simandou Range of Forestiere Province, Guinea-Conakry. In identifying the c. 2,100 specimens gathered in the course of the inventory work, a species of Psychotria came to light that was identified, using Hepper (1963), as Psychotria djumaensis De Wild. The specimens concerned matched several other specimens from Upper Guinea identified under this name at Kew and cited by Hepper (see below).

As a footnote to his account of Psychotria djumaensis in West Africa, Hepper commented: “The identity of these specimens with the Congo species is at present tentative”. So it is not surprising that comparison of the Upper Guinea material (sensu White 1983), with that of Congolian and central Africa, from whence the type of P. djumaensis derives, showed a number of major character disjunctions (Table 1). These are sufficient to justify specific rank for the Upper Guinean material which is accordingly described as new below. Using Petit (1964), the material under discussion keys out, not to sect. Holostipulatae K. Schum. which contains P. djumaensis, but to sect. Paniculatae Hiern. This is largely due to the bifid, not entire, stipules, presumably not visible on the material available to Hepper. Psychotria sect. Paniculatae also contains the other lianescent species of Psychotria in Africa. The material under discussion keys out in this section as P. fractinervata E. M. A. Petit, an E African taxon, differing in many features from P. samoritourei, e.g. the non-climbing habit, the puberulent (not glabrous) inflorescence, the ciliate-margined calyx (not glabrous) and the 5-grooved endocarp (lacking grooves in P. samoritourei). It seems that Petit did not see the material of this taxon seen by Hepper (1963) since he appears not to have cited it (Petit 1964).

Table 1. Major characters distinguishing Psychotria samoritourei from P. djumaensis.
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The Loma-Man Highlands

Psychotria samoritourei appears restricted to the submontane forest of the central part of the Loma-Man Highlands that lie just to the SE of the better known Fouta Djalon Highland area. Also known as ‘Guinee Dorsale’ or the ‘Backbone of Guinea’, the highland geologically diverse mass of Loma-Man above the 500 m contour has a long axis of about 400 km that runs more or less parallel with and 200 km from the coast, from the high points of the Loma Mts and Tingi Hills (Sierra Leone, 1924 m and 1850 m respectively) in the West, to the Mts of Man (Ivory Coast e.g. Mt Tonkui, 1190 m) in the East. It extends roughly 200 km N – S at its widest point. Best known of the higher points is Mt Nimba (to 1750 m), at the border of Liberia, Guinea and Ivory Coast, a UNESCO World Heritage site and a major centre of Tropical African diversity. About 90% of Loma-Man, however, lies in Guinea, where the highest points are the Pic de Fon of the Simandou range (1650 m) and, near the border with Liberia, Ziama (1350 m). Other less well-known high points also exist, but are not documented here.

The Southern third of Loma-Man, including Ziama, Nimba, Man and the southern tip of Simandou are found within the forest belt, while the remainder are located in the drier savanna belt to the North. However, the submontane areas outside the forest belt have forest sustained by orographic generated precipitation.

Botanical inventory and vegetation survey work of Loma-Man was mainly carried out in the middle decades of the 20th Century and led by Adam, Schnell and Jaeger (Adam 1971 – 1983; Jaeger & Adam 1980, 1981), the Man highlands themselves being explored by Aké Assi (2001, 2002).

The forest of the lower part of Loma-Man, i.e, up to about 500 – 1000 m altitude, hosts species restricted to the Upper Guinea forest generally, which extends from Senegal to Ghana. Above this altitude submontane forest occurs, with a different composition, and including some species apparently restricted to Loma-Man such as Psychotria samoritourei. Other examples are: Uapaca chevalieri Beille (Euphorbiaceae), Monanthotaxis nimbana (Schnell) Verdc. (Annonaceae), Phragmanthera assiana (Balle) Wiens & Polhill (Loranthaceae), Trichilia djalonis A. Chev. (Meliaceae), Shirakiopsis aubrevillei (Leandri) H. J. Esser (Euphorbiaceae) and a possible new species of Hibiscus. However the submontane forest of Loma-Man is dominated by a small number of lowland tree species which, at higher altitude become frequent, notably Parinari excelsa.

Fouta Djalon has close links with Loma-Man. It was explored botanically before Loma-Man, beginning with Heudelot in 1837 (Keay 1954: 6) and is better known for its endemic species. However, as Loma-Man became explored, several of the Fouta Djalon specialities, such as the monotypic genus Djaloniella P. Taylor, were discovered in the adjacent parts of Loma-Man. Since Loma-Man and Fouta Djalon are connected by a land bridge at 500 m altitude, the case for maintaining them as separate phytogeographic entities is weak and getting weaker as plant distributions become better known.

Species discovery in Guinea

Psychotria samoritourei is among a host of new species that have been brought to light and published from Guinea in the last six years, following a period of relative inactivity. Examples of such newly discovered species are: Xysmalobium samoritourei Goyder (2009), Gymnosiphon samoritoureanus Cheek (Cheek & van der Burgt (2010), Eriosema triformum Burgt (van der Burgt et al. 2012), Brachystephanus oreacanthus Champl. (Champluvier & Darbyshire 2009), Striga magnibracteata Eb. Fisch. & I. Darbysh. (Fischer et al. 2011), Eriocaulon cryptocephalum S. M. Phillips & Mesterházy (2015) and Napoleonaea alata Jongkind (Prance & Jongkind 2015).

Materials and Methods

The herbarium specimens researched for this paper were studied using a Leica MZ6 dissecting microscope equipped with an eyepiece graticule measuring in units of 0.02 mm. The technical illustration comprising Fig. 1 was made with the same equipment equipped with a Camera Lucida.

Fig. 1
figure 1

Psychotria samoritourei. A habit, flowering branch; B habit, fruiting branch; C interpetiolar stipules; D midrib from lower surface of leaf-blade, showing domatia; E long-styled flower, side view; F long-styled flower, corolla opened to show the stamens; G calyx limb opened out, showing inner surface with colleters; H long-styled flower with corolla removed, showing calyx and gynoecium; J short-styled flower, side view, calyx and gynoecium absent; K short-styled flower with corolla removed, showing style; L fruit, side view; M fruit, transverse section; N endocarp, adaxial surface; P seed, outer surface. A, C – H from Tchiengue 2675; B, L – P from Harvey 287; J & K from Van Der Burgt 825. drawn by andrew brown.

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All specimens cited in this paper have been seen unless indicated as “n.v.”. Location of unseen specimens has been inferred by reference to the distribution of specimens for collectors as listed in Hepper & Neate (1971) or for Adam’s Mt Nimba specimens, from his own citations (Adam 1975: 1036). HNG is newly registered in Index Herbariorum (Thiers, continuously updated) as the National Herbarium of Guinea-Conakry at the University of Gamal Abdel Nasser, Conakry. All other herbaria codes cited in this paper are also taken from that reference.

Psychotria samoritourei Cheek sp. nov. Type: Liberia, Mt Nimba, 700 m, fr., 10 Jan. 1965, J. G. Adam 20548 (holotype K; isotypes P n.v., UPS n.v.).

http://www.ipni.org/urn:lsid:ipni.org:names:60471717-2

Psychotria djumaensis sensu Hepper (1963: 202); Adam (1975: 1036, 1291 t. 615) non De Wild. (De Wildeman 1906: 349).

Climber to at least 10 m, and possibly 20 m, tall, vegetatively glabrous apart from stipular colleters. Stems terete when live, drying with longitudinal angles, fistular, twisting from left to right, second internode from apex (7 –) 9 – 14 cm long, 3 – 7 mm diam. below the third node from the apex, smooth, dull green, eventually ageing glossy blackish green. Leaf-blades drying papery, green on both surfaces, elliptic, rarely lanceolate, 3.6 – 11.7 × 1.7 – 5.5 cm, the smallest leaves (c. 3.6 – 4.5 × 1.7 cm) generally subtending the inflorescences and sometimes the partial-inflorescences (see discussion), acumen weakly differentiated, c. 1 cm long, base obtuse or acute, slightly decurrent in larger leaves, often asymmetric; midrib orange-brown, slightly depressed on the upper surface, raised below; lateral nerves 5 – 8 on each side of the midrib, ascending, inserted at c. 45° from the midrib and nearly reaching the margin, decurrent down the midrib to the nerve below, domatia tunnel-like, glabrous (Fig. 1D); tertiary nerves inconspicuous. Petiole articulated with the stem; with upper surface flat, lower surface convex, (3 –) 8 – 20 mm long, 1 – 2 mm wide. Stipule with sheath c. 1 mm long, interpetiolar part transversely oblong, c. 4 × 5 mm, apex biacuminate, the cleft c. 1.5 mm deep, narrow, the two lobes often appearing connivent when live, inner surface with a few small scattered colleters. Inflorescences of 100 – 200 white, less usually yellowish white or yellowish pink flowers, of which 6 – 7 are open at one time, terminal on the main stem and also on the pair of short branches that usually arise at the node below the main stem apex, the combined inflorescences forming a flat-topped compound inflorescence up to 15 cm diam. (Cheek field obs. July 2006); each inflorescence 3.5 – 7 × 3.5 – 8 cm, sessile, usually with three primary branches each with partial-peduncles 1.5 – 5 cm long, those of the lateral primary branches longer than and overtopping the main branch; rhachis 3 – 6 mm long; bracts lanceolate-triangular, 1 – 3.5 mm long; secondary branches 1 – 2 pairs, c. 5 mm long, rhachis c. 2 mm, bracteoles triangular, c. 1 × 1 mm; tertiary branches 3, 1.5 – 3.5 mm long, dilating gradually towards the 2 mm wide apex, bearing 3 branches at the apex, bracteoles c. 0.5 mm long; quaternary branches each 0.5 – 1 mm long, 1 – 3-flowered. Pedicels 0.5 – 1 mm long. Flowers hermaphrodite, 5-merous, heterostylous, scent not detected at 9 am (Cheek personal observation 2006). Calyx limb-tube campanulate, c. 2.5 mm long, limb c. 1.5 mm long, margin with 5 triangular lobes each 0.5 mm long, the sinuses curved, inner surface with a few scattered colleters. Corolla white, long-tubed flowers, c. 6 × 3 mm, throat occluded by white hairs, hairs 1 – 3 mm long, occupying a band 1.75 – 2 mm deep; lobes nearly patent, 2 – 2.5 – 1.5 mm, apex acute, lacking hood and appendage. Stamens with anthers 1 mm long, included, on free filaments (attached to middle part of corolla tube) 1 mm long glabrous. Style exserted c. 6 mm long, pubescent; stigma lobes 0.7 –1 mm long, verrucate. Disc subglobose, 0.9 – 1 × 0.9 – 1.25 mm, style inserted into an apical aperture. Short-styled flowers with corolla tube 7.5 × 4 mm, lobes 3 – 3.5 × 2 mm. Stamens with anthers 1.5 – 2 mm long, exserted by 0.5 – 2 mm, free filaments c. 4 mm long. Style included, c. 3 mm long, stigma lobes 1 – 1.5 mm long. Disc not seen (only fallen corolla-androecia available). Infructescence about as large as inflorescence, with 20 – 50 drupes, mature drupes glossy orange, globose 0.5 – 0.7 cm diam., with c. 4 – 10 longitudinal white lines, which dry as grooves; fruiting pedicel c. 2 × 2 mm; calycular remains c. 1 mm long, erect; pyrenes orbicular in plan view c. 6.5 – 8 mm diam., hemispherical to oblong in transverse section, 3 – 3.5 mm deep, lacking ridges or grooves, pre-formed germination slit absent. Seeds plano-convex, slightly smaller than the pyrene, ruminate on all surfaces, without groove on inner face. Fig. 1.

recognition. Psychotria samoritourei Cheek differs from P. djumaensi De Wild. being a liana, not being a shrub or tree, and in having the stipule bifurcate (not entire), inhabiting well-drained submontane forest, not lowland swamp forest.

distribution. Loma-Man Highlands of Upper Guinea: Guinea-Conakry, Sierra Leone and Liberia.

habitat. Submontane evergreen forest; 550 – 1470 m altitude.

specimens examined. guinée (conakry). Mt Nimba, Crête Nimba, clairière de la piste de Tuo á Yalé, fl. June, J. G. Adam 26053 (P n.v.); Macenta and Beyla area, Simandou Range, Pic de Fon area; forest plot Y3, adjacent to Elephant Rock, 8°32'03''N, 8°54'08''W, 1380 m, fr., 7 Nov. 2005, Harvey – Y series (plot voucher) 86 (K, HNG); Forest at Elephant Rock, transition with grassland, WSW facing, 8°31’58.5”N, 8°54'88.4''W, 1160 m, fr., 13 Nov. 2005, Harvey 287 (K, HNG); Elephant Rock, road leading to Whisky 2, 8°32'03''N, 8°54'25''W, 1380 m, fl., 2 July 2006, Tchiengue 2675 (BR, HNG, K, MO, WAG); Dabatini, NE ridge, 8°33'22''N, 8°54'20''W, 1470 m, fl., 3 July 2006, Van Der Burgt 825 (HNG, K). sierra leone. Bumbuna: 650 m, fr., 14 Oct. 1914, Thomas N. W. 3406 (AAH, BR, FHO all n.v., K, P n.v.); ibid 650 m, fr., 20 Oct. 1914, Thomas N. W. 3673 (AAH, BR, FHO all n.v., K, P n.v.). liberia. Mt Nimba, Central Province, Sanokwele Distr., Ganta, fl., yng fr., 17 May 1935, Harley W. J. 1178 (BM n.v., GH n.v., K, LIB n.v., MO n..v., US n.v.); Eastern Province, Tchien Distr., Cess R., near Bahtown, fl., 12 Aug. 1947, Baldwin 9014 (BM, COI, both n.v., K, MO n.v., US n.v.); Central Province, Sanokwele Distr., Ganta, fr., 15 Sept. 1947, Baldwin 9317 (BM, COI, both n.v.., K, MO n.v., US n.v.); Mt Nimba, route Yéképa-la mine, 700 m alt., fr. Dec., J. G. Adam 20345 (P n.v.); Yiti valley, 900 m alt., fr., 10 Jan. 1965, J. G. Adam 20548 (K, P n.v., UPS n.v.); Geologists’ camp 1350 m alt., fl. buds, June, J. G. Adam 21537 (P n.v.); environs de Grassfields, 550 m alt., fr. Dec. J. G. Adam 25269 (P n.v.); Yiti Valey, 900 m alt., fl. June, J. G. Adam 25788 (P n.v.).

conservation. Psychotria samoritourei is here assessed using the criteria of IUCN (2012) as Vulnerable (VU B1 a,b(iii)), based on the data presented below. P. samoritourei is known from seven collections at three sites in Liberia, apparently all in the general Mt Nimba area. In Sierra Leone it is known from two collections at one site in the NE, Bumbuna, and in Guinea-Conakry from one collection at Mt Nimba, several at Ziama, and four collections at two sites, both within a few km of each other, in the Pic de Fon-Dabatini area of the Simandou ridge in Guinea. At Simandou we found it to be locally fairly common being conspicuous in the forest canopy in July in stunted ridge top forest due to its large flat-topped white inflorescences. It is most easily observed like many lianas, at the forest edge, since then it will flower as little as a metre from ground.

The area of occupancy of this species is here estimated as 1840 km2. Fourteen specimens, representing seven locations are currently known. Given habitat destruction at its sites in the Mt Nimba area of Liberia due to past and planned open cast mining for Iron (formerly by LAMCO, currently by Mittal Steel), and planned open cast mining at the Mt Nimba area of Guinea by BHP-Billiton/EuroNimba, at Bumbuna (planned World Bank supported hydroelectric dam) and at Simandou (Opencast iron mining under planning by Rio Tinto), it is here considered that significant threats to the habitat of this species exist.

It is likely that Psychotria samoritourei also occurs in other areas of submontane forest in the Loma-Man Highlands (see discussion below) of Upper Guinea which have been less completely surveyed than those for which specimens have been cited. Should these be discovered, it is possible that the threat status of this species will be reduced. Potentially any site above 550 m alt. (the lowest known altitude for the species) in Loma-Man with evergreen forest might yield this species. Three collections of Psychotria samoritourei were discovered in the intensive survey work in the Loma Mts (Jaeger & Adam 1980, 1981), while eight collections are known from the Mt Nimba area (Adam 1971 – 1983), which appears to be the stronghold for the species. The species has not been found in the Man Mts, despite survey work there by Aké Assi, indeed, it is so far unknown from Ivory Coast (Aké Assi 2001, 2002).

local names & uses. None are known.

etymology. Psychotria samoritourei is named in honour of Samori Touré c. 1830 – 1900, the founder of the Wassoulou Empire which resisted European colonial rule in West Africa from 1882 to his capture in 1898 (Wikipedia contributors 2006).

Taxonomic affinities

Several features of Psychotria samoritourei are shared with P. djumaensis, making it easy to see why its placement there has remained unchallenged for over 40 years: diffuse, flat-topped highly floriferous inflorescences, fistular stems, articulated petioles and tunnel-like domatia. The major characters differentiating the two species are listed in Table 1 below. However, according to Petit’s (1964) sectional classification, the true affinities of P. samoritourei appear to be with the other African lianescent species in sect. Paniculatae.