Introduction

The genus Lychnodiscus Radlk. (Sapindaceae) occurs in tropical Africa and is largely restricted to the Guineo-Congolian region, from the Republic of Guinea (Gosline et al. 2023a, 2023b) to S Sudan (Darbyshire et al. 2015) and southwards to Uganda (Davies & Verdcourt 1998) and Democratic Republic of the (DR) Congo (Hauman 1960). It is easily recognised, among African Sapindaceae, by its actinomorphic flowers (many other African genera of the family are zygomorphic) in which there are two concentric discs, often resembling a cup and saucer (in other genera there is usually no more than one disc). The five sepals are quincuncially imbricate, united at the base. The ovary is 3-locular with a distinct style, the locules are uniovulate. The fruit is dehiscent, the inside of the three leathery valves is red or pink and glabrous and the three large seeds entirely covered in a glossy, sometimes sticky, red or orange aril or seedcoat, so that we conjecture that they are likely dispersed by primates.

Lychnodiscus has been placed, until recently, in the standard tribal classification of the family (Radlkofer 1932), in the pantropical tribe Cupanieae Radlk., which included 40 genera, five of which are in Africa (Fouilloy & Hallé 1973a, 1973b): Aporrhiza Radlk., Laccodiscus Radlk., Lychnodiscus, Eriocoelum Hook.f., and Blighia K.D.Koenig. The tribe was characterised by uniovulate locules; paripinnate leaves (although saplings of Lychnodiscus and Laccodiscus often have simple leaves); loculicidally dehiscent fruit, often with fleshy valves (Radlkofer 1932); the flowers are usually regular; the petals with an adaxial scale that is bifid or united to the limb to form a funnel (Fouilloy & Hallé 1973a, 1973b). However, recent molecular phylogenomic studies (Buerki et al. 2021; Joyce et al. 2023), based on over 300 nuclear genes, have demonstrated the polyphyly of Cupanieae in the sense of Radlkofer (1932), which genera are scattered in various clades in phylogenetic trees with high support. A realignment of tribes in Sapindaceae was, therefore, provided by Buerki et al. (2021). The position of Lychnodiscus, unfortunately not yet included in any molecular analyses, remains uncertain, but we conjecture that its closest relatives probably include Aporrhiza and Laccodiscus, both of which differ from Lychnodiscus by their simple disk and bicoloured seeds (orange at base, black at apex). Aporrhiza, which shares with Lychnodiscus the very unusual character of a radicle opposite the hilum, may also be separated by its 2-locular ovary and valvate sepals, while Laccodiscus has fruit valves hirsute inside, an inferior radicle, petals lacking an internal scale (but with lateral appendages) and leaves often with pseudostipular lower leaflets. Aporrhiza and Laccodiscus are in the same subclade, with the non Cupanieae genera Pancovia Willd., Placodiscus Radlk., and Haplocoelopsis F.G.Davies), of Buerki et al. (2021) and Joyce et al. (2023). This subclade, all genera being tropical African, is part of clade 9, comprising the redelimited tribe Nephelieae of Buerki et al. (2021), currently with 16 genera including 116 species. However, as newly reconstituted, there is as yet no morphological delimitation of this tribe available: “We have not yet identified any morphological synapomorphies that define this clade” (Buerki et al. 2021, pp. 1243 – 1244). We consider that Lychnodiscus is likely to be placed in Nephelieae with these genera when eventually the genus is included in molecular studies.

Like many genera of African Sapindaceae, Lychnodiscus has not been revised as a whole since Radlkofer (1932), although regional treatments have been published for W Africa (Keay 1958), Cameroon and Gabon (Fouilloy & Hallé 1973a, 1973b), DR Congo, Rwanda and Burundi (Hauman 1960) and East Africa (Davies & Verdcourt 1998). Seven species of Lychnodiscus are currently accepted (Lebrun & Stork 1992; African Plant Database continuously updated; POWO 2022, continuously updated): L. brevibracteatus Fouilloy, L. cerospermus Radlk. (with three varieties), L. dananensis Aubrév. & Pellegr., L. grandifolius Radlk., L. multinervis Radlk., L. papillosus Radlk., and L. reticulatus Radlk. Two species are recorded from W Africa (Keay 1958), two from Cameroon (Fouilloy & Hallé 1973a), two from Gabon (Fouilloy & Hallé 1973b; Lachenaud et al. 2018) and two also from DR Congo (Hauman 1960). The genus is most taxon-diverse in DR Congo, with four taxa (Hauman 1960). However, the genus is under-researched, for example, until recently (Lachenaud et al. 2018), of the eight specimens of Lychnodiscus listed for Gabon (Sosef et al. 2006) only one was identified to species.

Lychnodiscus species are shrubs to medium-sized trees and occur mostly in lowland forest. Species of the genus are usually infrequent within their ranges and occur as isolated individuals, although L. grandifolius may be locally common in Gabon (Lachenaud et al. 2018). L. cerospermus, although it occurs also at low altitudes, is unusual in that it is found in the understorey of forest at 1000 –1500 m in altitude which is often inundated for part of the year (Bosch 2012). Eilu et al. (2004), in their study of four forests in the Albertine Rift of Uganda, enumerated 212 tree species of diameter above 10 cm at 1.5 m above ground, assessing the rarity status of each species; L. cerospermus was among the four rarest species, having both a restricted range and low population density.

Few species of Lychnodiscus have recorded uses, apart from firewood (Burkill 2000). However, the wood of L. cerospermus is used in DR Congo for construction and to make mortars (Bosch 2012). Young leaves of the same species are consumed by chimpanzees in the Budongo Forest of western Uganda, but are not a major part of their diet (Bates 2005), perhaps because of the rarity of these trees.

In connection with the Cameroon Tropical Important Plant Areas programme (Darbyshire et al. 2017; Murphy et al. 2022, 2023), in May 2022, two specimens from the Bali Ngemba Forest Reserve, Ghogue 1080 and Cheek 10503 (both K!), that had been identified in Harvey et al. (2004) as Lychnodiscus grandifolius Radlk., were reviewed. Although previously unambiguously identified as this species, the specimens had been annotated “Possibly a montane form, 6 not 5-jugate, leaves narrower, hairy on midrib and veinlets, rachis—not glabrous” by the first author. The third author, in the course of reviewing Lychnodiscus grandifolius in the context of species range extensions into Gabon, had later added the annotation “Presumably sp. nov. differs from grandifolius by leaves sparsely pubescent beneath and lacking glandular dots; flowers larger; calyx and ovary with long golden-brown indumentum (vs. very short indumentum); montane habitat”. In Lachenaud et al. (2018) it is stated: “Collections from the western Cameroon highlands, previously identified as L. grandifolius (e.g. Cheek et al. 2004: 399) appear to represent two new taxa. The first of these, from Bali Ngemba F.R. (Cheek 10503; Ghogue 1080) differs from L. grandifolius by the longer indumentum of the leaflets, inflorescences and ovaries, the absence of leaf glands, and the larger flowers. The second taxon, from Mt Muanenguba, is only represented by a poor fruiting specimen (D. W. Thomas 3110) which differs from L. grandifolius by the larger size and dark brown indumentum of the fruits.” Further research showed additional characters separating the Bali Ngemba high altitude taxon from the lowland L. grandifolius (see below) and the former is here described as a new species, Lychnodiscus bali. The Manenguba taxon referred to is not addressed further here, being only represented by incomplete fruiting material, and further collections not being possible due to the ongoing warfare in the NW and SW Regions of Cameroon.

Materials and Methods

Specimens were collected using the patrol method and processed as documented in Cheek & Cable (1997). Identifications were made following Cheek (2023). Herbarium acronyms follow Index Herbariorum (Thiers 2022, continuously updated). All specimens were seen by one or more authors. Specimens of Lychnodiscus were studied at BR, BRLU, K, LBV, P, WAG and YA. The National Herbarium of Cameroon, YA, was specially searched for additional material of the new taxon, as was Tropicos (http://legacy.tropicos.org/SpecimenSearch.aspx). Images for WAG specimens, now at Naturalis, were studied at https://bioportal.naturalis.nl/?language=en and those from P at https://science.mnhn.fr/institution/mnhn/collection/p/item/search/form?lang=en_US. We also searched JStor Global Plants (2022) for additional type material of the genus not already represented at K.

Binomial authorities follow the International Plant Names Index (IPNI continuously updated). The conservation assessment was made using the categories and criteria of IUCN (2012). Herbarium material was examined with a Leica Wild M8 dissecting binocular microscope fitted with an eyepiece graticule measuring in units of 0.025 mm at maximum magnification. The drawing was made with the same equipment using a Leica 308,700 camera lucida attachment. Flowers from herbarium specimens of the new species, described below, were soaked in warm water to rehydrate the flowers, allowing dissection, characterisation and measurement. The description follows the terms in Beentje & Cheek (2003), format and conventions follow Cheek et al. (2021a).

Taxonomic Treatment

Key to the species of Lychnodiscus

1. Leaves entirely glabrous; midrib of leaflets strongly raised above; stems cylindrical (Cameroon, Gabon) ………………………………………………………………………………………………………………… L. brevibracteatus

1. Leaves with at least some hairs on the rachis and lower surface of nerves; midrib of leaflets usually flat or impressed above; stems usually 5-sulcate ……………………………………………………………………………… 2

2. Lower leaf surface covered with dense greyish to brownish papillae ……………………………………………… 3

2. Lower leaf surface green, with papillae absent or very sparse ……………………………………………………… 4

3. Leaflets entire or slightly toothed in upper third; pedicels 5 – 9 mm long at anthesis; calyx 5 – 6 mm long (Guinea to Ghana) …………………………………………………………………………………………………… L. dananensis

3. Leaflets with conspicuous, often spinescent teeth; pedicels 2 – 5 mm long at anthesis; calyx 4 – 5 mm long (Congo Republic, DR Congo) …………………………………………………………………………… L. papillosus

4. Leaflets with conspicuous glandular dots, scattered on lower surface; inflorescence usually with dark brown indumentum (Cameroon, Equatorial Guinea, Gabon) …………………………………………… L. grandifolius

4. Leaflets without glandular dots; inflorescence with greyish to golden-brown indumentum; …………………… 5

5. Calyx 5.5 – 7 mm long; leaflets entire ………………………………………………………………………………… 6

5. Calyx 2.5 – 4 mm long; leaflets usually strongly dentate, rarely ± entire in L. cerospermus ………………………… 7

6. Leaflets with 9 – 12 pairs of secondary veins; petals longer than broad and exceeding the sepals, the latter ± erect at anthesis; stamen filaments hairy (W Cameroon) …………………………………………………………… L. bali

6. Leaflets with 17 – 25 pairs of secondary veins; petals broader than long, not exceeding the sepals, the latter spreading at anthesis; stamen filaments glabrous (eastern DR Congo) ……………………………… L. multinervis

7. Stamen filaments hairy; tertiary leaf veins reticulate (Ivory Coast to Nigeria & Equatorial Guinea (Bioko)) ……………………………………………………………………………………………………………………… L. reticulatus

7. Stamen filaments glabrous; tertiary leaf veins scalariform (Gabon to Uganda) ………​………… L. cerospermus

Lychnodiscus bali Cheek sp. nov. Type: Cameroon, North West Region, Mezam Division, Bali Ngemba Forest Reserve, path from first valley to highest point of reserve, 5°48′52"N, 10°05′00"E, fl. & fr., 13 Nov. 2000, Cheek 10503, with Biye, Nana, Iwanaka, Wanduku, Ach Nkankanu, van de Rheede, Garcia, Sama & Tadjouteu (holotype K [K000746446]; isotypes BR, MO, WAG [WAG0424201], YA).

http://www.ipni.org/urn:lsid:ipni.org:names:77342251-1.

Lychnodiscus grandifolius sensu Cheek et al. (2004: 125) non Radlk.

Shrub or tree, 5 m tall, sparsely branched. Stem subterete or slightly 5-sulcate, 7 – 14 mm diam. at distal flowering nodes, densely pubescent with golden-brown patent to ascending hairs 0.025 – 0.75 mm long; lenticels dark brown, orbicular 0.25 – 0.75 mm. Leaves alternate, pinnately compound, 48 – 50 × 38 – 40 cm, 5- to 6-jugate, rachis internodes plano-convex 3.5 – 6 cm long, indumentum as stem. Leaflets chartaceous, entire, discolorous, drying grey-green to grey-black on adaxial surface and pale brown on abaxial surface, opposite or subopposite, terminal leaflet vestigial 1 – 2 × 1 – 2 mm, median leaflets larger than proximal or distal. Proximal leaflet pair smallest, elliptic, 9.5 – 11.5 × 4 – 5.5 cm, apex obtuse or with a small acumen c. 2 2 mm, base acute, midrib and lateral nerves impressed on adaxial surface, abaxial glands and domatia absent, lateral nerves c. 9 on each side of the midrib, tertiary nerves subscalariform, quaternary nerves reticulate, conspicuous and raised below, hairs patent, dull brown to whitish, simple, 0.25 – 0.5 (– 1) mm long, moderately dense on nerves and sparse between them. Median leaflet pairs as the proximal leaflets, but oblong-elliptic, 16.5 – 20 × 6.5 – 7.5 cm, apex obtuse to rounded, base obtuse to acute, slightly asymmetric, lateral nerves 10 – 12 pairs. Terminal leaflet pair obovate, 11.5 (– 18) × 5.8 cm, apex rounded, base acute, lateral nerves c. 10 pairs. Petiolules stout, subconical, dorsiventrally compressed, 4 – 5 mm long, 2 – 6 mm wide at base, 1.5 – 4 mm wide at apex, blade decurrent to the distal margins, densely hairy as stem. Petiole drying dark brown, terete, base thickened and decurrent, 11 – 11.5 × 0.3 – 0.6 cm, indumentum as stem. Inflorescence paniculiform, terminal and axillary in distal nodes, thyrsoid, 41 – 66.5 × 22 – 28 cm, peduncle 6 – 12 × 0.4 – 0.6 cm; rachis 34.5 – 57.5 × 0.3 – 0.5 cm, internodes 2.5 – 6.5 cm long, partial-inflorescences (secondary inflorescences) 6 – 31, most proximal partial-inflorescence 14 – 26.5 cm long each with 9 – 13 secondary partial-inflorescences, each 1 – 3 cm long, 3 – 6-flowered; distal 20 – 25 partial-inflorescences 1.5 – 4 cm long; bracts linear-oblong to narrowly triangular, patent (3 –) 5 – 6 × 1 mm; bracteoles as the bracts, 2 – 3 mm long, indumentum of bracts and bracteoles as stem, dense. Pedicels (3 –) 5 – 6 × 1 – 1.5 mm, articulate at base, indumentum as stem. Flowers hermaphrodite, actinomorphic. Sepals 5, imbricate in bud, erect or oblique at anthesis, polymorphic (different in indumentum), oblong-ovate 6.5 – 7 × 4.5 mm, connate at base for c. 1 mm, apex obtuse, outer surface densely and stiffly hairy as pedicel, except the marginal 1 mm of both sides of the two inner sepals and one side of the intermediate sepal with shorter crisped hairs, inner surface densely and shortly pubescent. Petals 5, white in life, drying red-brown, slightly exserted from the sepals at anthesis, unguiculate, obovate or elliptic, 8 – 9 × 3 – 4 mm, apex broadly rounded, distal third to half of petal sparsely to moderately hairy on adaxial surface, glabrous adaxially or with a few hairs along the midrib; proximal third to half of petal narrowing gradually towards base, adaxial surface glabrous, abaxial densely hairy; basal claw c. 2 mm long, 1 mm wide, glabrous on both surfaces. Inner appendage of petals inserted c. 5.5 mm from the base, transversely oblong, as wide as petal, 1.5 mm long, revolute, densely puberulent at the base on both surfaces, hairs translucent; the distal part of the appendage glabrous on both surfaces. Stamens 8 – 9, free, equal, 6 – 7 mm long, filaments cylindrical, 4.5 – 5 × 0.4 mm, slightly curved or straight, densely villose with patent, translucent simple hairs 0.2 – 0.5 mm long, anther dull white, basifixed, more or less oblong, 1.8 × 1 × 0.75 mm, latrorse and introrse, dorsal surface with the two thecae separated by a broad connective, connective sometimes with a few hairs as the filament. Discs 2, closely surrounding the base of the ovary, outer disc 5 mm wide, inner disc c. 4 mm wide, raised above the outer, both discs red, erect, thin, crenate c. 0.3 – 0.5 mm long. Ovary superior, 3-locular, trigonous-rounded, 5 × 4 mm, densely yellowish-brown hairy, hairs erect, 0.5 – 0.75 mm long. Style cylindrical, stout, 2 × 1 mm, indumentum as ovary; stigma barely 3-lobed, glabrous. Fruit and seed not seen. Fig. 1.

Fig. 1
figure 1

Lychnodiscus bali. A habit, leaf, inflorescence and portion of stem from near stem apex; B abaxial leaf surface (detail); C partial-inflorescence showing partial-peduncle, bracts and flowers; D immature fruit; E flower, side view; F flower with proximal sepals and petals removed; G petal adaxial view; H petal abaxial view; J double disc and base of filaments; K – L stamens, respectively side, abaxial and adaxial views; N ovary transverse section. All from Ghogue 1080. drawn by andrew brown.

recognition. This species resembles Lychnodiscus grandifolius in its entire leaflets, hairy stamen filaments, and petals longer than broad and exceeding the sepals, the latter ± erect at anthesis. All other species of the genus have petals broader than long and at most equalling the sepals, which are ± patent at anthesis and, except in L. reticulatus, their filaments are glabrous. The new species differs from L. grandifolius in the shorter length of the distal leaflets (12 – 18 cm vs 22 – 39 cm long), in the abaxial surface lacking glands (vs with conspicuous, scattered, flat glands), in having sparse hairs all over (vs glabrous except primary and secondary veins) and in the larger flowers, 8 – 11 mm long at anthesis (vs 5 – 7 mm long). Additional diagnostic characters are given in Table 1.

Table 1. Characters separating Lychnodiscus grandifolius from L. bali.

distribution & habitat. Endemic to the Bali Ngemba Forest Reserve in the Bamenda Highlands in the North Western Region of Cameroon at an altitude of 1700 – 1950 m. The species grows with Hannoa ferruginea (Simaroubaceae), Rhaphiostylis beninensis (Metteniusaceae), Pentas ledermanni, Psychotria subpunctata, Rothmannia urcelliformis, Cuviera longiflora, (all Rubiaceae), Synsepalum brevipes (Sapotaceae), Cyperus renschii var. renschii (Cyperaceae), Pseudognaphalium luteo-album (Compositae), Adenia cf. cissampeloides (Passifloraceae), Ficus ardisioides subsp. camptoneura (Moraceae), Amorphophallus staudtii (Araceae), Stephania abyssinica var. abyssinica (Menispermaceae), Aframomum sp. 1 of Bali Ngemba (Zingiberaceae), Pseudospondias microcarpa (Anacardiaceae). In disturbed areas (see Notes below).

specimens examined. cameroon. NW Region: Bali Ngemba Forest Reserve, Mantum to Pigwin (sic.), 1950 m, fl., 11 Nov. 2000, Ghogue 1080, with Julia Garcia, Christo Van de Rheede, Benedict Pollard, Emmanuel Sama, Petula Nabukeera, Francis Njie (K [K000746448], P, YA); path from first valley to highest point of reserve, 5°48′52"N, 10°05′00"E, fl. & fr., 13 Nov. 2000, Cheek 10503, with Biye, Nana, Iwanaka, Wanduku, Ach Nkankanu, van de Rheede, Garcia, Sama & Tadjouteu (holotype K [K000746446]; isotypes BR, MO, WAG [WAG0424201], YA).

conservation status. Lychnodiscus bali is known from two collections within 1 – 2 km of each other representing a single location (sensu IUCN 2022) in the higher altitudes of the Bali Ngemba Forest Reserve in NW Region of Cameroon. The Area of Occupancy (AOO) is calculated as 4 km2 using the preferred IUCN grid cell size of 2 × 2 km (IUCN 2012, 2022). The Extent of Occurrence (EOO) should be equal to the AOO to ensure consistency with the definition of AOO as an area within EOO (IUCN 2012). Furthermore, less than 50 mature individuals have been observed. Plotting the grid reference of the two specimens on Google Earth (https://earth.google.com) and examining historic imagery shows that there is an increase in cleared areas of forest, likely due to the creation of more agricultural land by the local community, which was observed by the first author when collecting the type specimen. Furthermore, the Bali Ngemba Forest Reserve to which the species seems to be restricted is the only significant submontane forest surviving in the Bamenda Highlands. The Bamenda Highlands have seen > 95% loss of the original forest cover (Cheek et al. 2000; Murphy et al. 2022, 2023). This justifies a preliminary conservation assessment of Critically Endangered [CR B1ab(iii) + B2ab(iii) + D], in accordance with the IUCN Red List Categories and Criteria (IUCN 2012).

This distinctive and, in flower, conspicuous, small tree has not been found in surveys elsewhere in the Cameroon Highlands and adjacent areas (Cheek 1992; Cheek et al. 1996, 2000, 2004, 2006, 2010; Cable & Cheek 1998; Maisels et al. 2000; Chapman & Chapman 2001; Harvey et al. 2004, 2010; Cheek et al. 2011). The new species should be included in the next edition of the Red Data Book of Cameroon Plants (Onana & Cheek 2011).

etymology. The species epithet refers to the Bali Ngemba Forest Reserve, to which it appears to be endemic.

local names & uses. None is known.

notes. Lychnodiscus bali appears to be an ecological pioneer, benefitting from limited disturbance since both specimens were found in areas that had been previously cleared of forest for agriculture and were then regenerating as “farmbush”, or even with some crops still present. The similar Lychnodiscus grandifolius also occurs in disturbed areas (Lachenaud et al. 2018). Lychnodiscus bali has the highest altitudinal range of any species in the genus (1700 – 1950 m alt.).

Discussion

Lychnodiscus bali is the most recent of several new species of Sapindaceae to have been described from surveys in Cameroon, mainly from the Cameroon Highlands, other species are Allophylus ujori Cheek (Cheek & Etuge 2009a), Deinbollia oreophila Cheek (Cheek & Etuge 2009b), Allophylus bertoua Cheek (Cheek & Haba 2016) and Deinbollia onanae Cheek (Cheek et al. 2021a, b). There is no doubt that additional new species remain to be discovered in Cameroon, in this family, which in tropical Africa is taxonomically under-researched.

The discovery from Bali Ngemba of Lychnodiscus bali is the latest of a steady stream of taxonomic novelties from this small, threatened remnant of submontane forest in the Bamenda Highlands. Other recently published species from Bali Ngemba have been Vepris onanae Cheek (Cheek et al. 2022b), Monanthotaxis bali Cheek (Cheek et al. 2023b) and Deinbollia onanae Cheek (Cheek et al. 2021a, b). To date, 34 threatened species are recorded from this forest, of which nine are strict endemics and 11 near-endemics (Cheek et al. 2023b).

The discovery of this new species among the specimens in the Kew Herbarium (K) supports previous evidence that the availability of, and ready access to, well-managed herbaria are important factors for completing our knowledge of the species on our planet (Bebber et al. 2010; Onana et al. 2017). However more trained taxonomists are needed to work on these collections, as well as in the field (Sutcliffe & O’Reilly 2010).

Lychnodiscus bali is the latest in a series of discoveries of new species to science from the forest habitats of the Cameroon Highlands. These species include epiphytic herbs, e.g. Impatiens frithi Cheek (Balsaminaceae, Cheek & Csiba 2002) and I. etindensis Cheek & Eb.Fisch. (Balsaminaceae, Cheek & Fischer 1999), terrestrial herbs, e.g. Brachystephanus kupeensis I.Darbysh. & Champl. (Acanthaceae, Champluvier & Darbyshire 2009) and Isoglossa dispersa I.Darbysh. (Darbyshire et al. 2011), rheophytes, e.g. Ledermanniella onanae Cheek (Cheek 2003) and Saxicolella ijim Cheek (Podostemaceae, Cheek et al. 2022a), achlorophyllous mycotrophs, e.g. Kupea martinetugei Cheek & S.A.Williams (Triuridaceae, Cheek et al. 2003) and Afrothismia amietii Cheek (Cheek 2007; Afrothismiaceae, Cheek et al. 2023a), understorey shrubs and small trees, e.g. Kupeantha kupensis Cheek (Rubiaceae, Cheek et al. 2018a) and Psychotria darwiniana Cheek (Rubiaceae, Cheek et al. 2009), climbers, e.g. Sabicea bullata Zemagho, O.Lachenaud & Sonké (Rubiaceae, Zemagho et al. 2014), Ancistrocladus grandiflorus Cheek (Ancistrocladaceae, Cheek 2000) and canopy trees, e.g. Microcos magnifica Cheek (Grewiaceae, Cheek 2017), Korupodendron songweanum Litt & Cheek (Vochysiaceae, Litt & Cheek 2002), Vepris montisbambutensis Onana (Onana & Chevillotte 2015), Vepris mbamensis Onana (Onana et al. 2019), Vepris zapfackii Cheek & Onana (2021) and Carapa oreophila Kenfack (Meliaceae, Kenfack 2011).

Most of these new species were first described as point or near-endemics, but several have, with more research, been found to be more widespread e.g. Tricalysia elmar Cheek (Rubiaceae, Cheek et al. 2020a) now known to extend from Mt Kupe and Bali-Ngemba to e.g. the Rumpi Hills (collection number Dessein et al. 2616). Mussaenda epiphytica Cheek (Rubiaceae, Cheek 2009), first only known from Bakossi, but then found elsewhere in Cameroon (Lachenaud et al. 2013) and now in Gabon (collection number Lachenaud et al. 3700). Coffea montekupensis Stoff. (Stoffelen et al. 1997) first thought to be endemic to Mt Kupe is now known to occur in the Tofala Sanctuary (Lebialem Highlands, Harvey et al. 2010). Oxyanthus okuensis Cheek & Sonké (Rubiaceae, Cheek & Sonké 2000) initially thought to be endemic to Mt Oku is now known to extend to Tchabal Mbabo (Lachenaud et al. 2013). It is to be hoped that the range of Lychnodiscus bali will be similarly extended by future research and its extinction risk assessment consequently reduced.

Conclusions

It is important to uncover the existence of previously unknown plant species as soon as possible and to formally name them. Until this is done, they are invisible to science and the possibility of their being assessed for their conservation status and appearing on the IUCN Red List is greatly reduced (Cheek et al. 2020b), limiting the likelihood that they will be proposed for conservation measures, and that such measures will be accepted, affording protection. Completing our knowledge of the world’s plant species was target one of the Global Strategy for Plant Conservation (https://www.cbd.int/gspc/default.shtml), leading to assessments of their conservation status (target two) and in situ conservation as Important Plant Areas (target five), although meeting these has been challenging (Paton & Nic Lughadha 2011). Although there are exceptions (Cheek & Etuge 2009b; Cheek et al. 2019a), most new plant species to science are highly range-restricted, making them almost automatically threatened (Cheek et al. 2020b).

Only 7.2% of the 369,000 flowering plant species (the number is disputed) known to science have been assessed on the IUCN Red List (Bachman et al. 2019; Nic Lughadha et al. 2016, 2017). However, the vast majority of plant species still lack assessments on the Red List (Nic Lughadha et al. 2020). Fortunately, Cameroon has a plant Red Data book (Onana & Cheek 2011), which details 815 threatened species, but it needs updating. Thanks to the Global Tree Assessment (BGCI 2021), many of the world’s tree species have now been assessed. The State of the World’s Trees concluded that the highest proportion of threatened tree species is found in Tropical Africa and that Cameroon has the highest number (414) of threatened tree species of all tropical African countries (BGCI 2021). This will be further increased by the addition of Lychnodiscus bali.

Concerns about global plant species extinctions are increasing as the biodiversity crisis continues. In Cameroon, the lowland forest species Inversodicraea bosii (Cusset) Rutish. & Thiv, Oxygyne triandra Schltr., Afrothismia pachyantha Schltr. have been considered extinct for some years (Cheek et al. 2017a, b; Cheek & Williams 1999; Cheek et al. 2018b, 2019b). Similarly, Pseudohydrosme bogneri Cheek & Moxon-Holt and P. buettneri Engl. are now considered extinct in lowland forest in neighbouring Gabon (Moxon-Holt & Cheek 2021; Cheek et al. 2021b). However, Cameroonian endemic, submontane (cloud) forest species are now also being recorded as globally extinct, such as the well-documented case of Vepris bali Cheek (Cheek et al. 2018c) also at Bali Ngemba Forest Reserve. Global species extinctions are being recorded from across Africa, from West (e.g. Saxicolella deniseae Cheek in Guinea (Cheek et al. 2022a) to East (e.g. Cynometra longipedicellata Harms, Kihansia lovettii Cheek and Vepris sp. A of FTEA in Tanzania (Gereau et al. 2020; Cheek & Luke 2022; Cheek 2004).

If such extinctions are to cease, or more realistically, to be slowed, improved conservation prioritisation programmes are needed, to firstly determine the most important plant areas for conservation (Darbyshire et al. 2017) and secondly to implement protection with local communities and authorities through well-drawn up management plans and resourcing. Cultivation and seedbanking of species at risk of extinction, if feasible, are important fall-back strategies, but conservation of species in their natural habitat must be the first priority.

The future of Lychnodiscus bali depends on greatly improved protection of the Bali Ngemba Forest Reserve which for years has seen steady encroachment, to the extent that at least one of its species is almost certainly globally extinct (Vepris bali) and another is feared likely to be extinct (Monanthotaxis bali, see above). It is hoped that recent listing of Bali Ngemba as an Important Plant Area (Murphy et al. 2022, 2023) will support better protection of this unique forest in future by local communities and administration.