118 urn:lsid:arphahub.com:pub:71cc5dc6-a767-5334-951f-ef6ae8936459 Plant Ecology and Evolution plecevo 2032-3913 2032-3921 Meise Botanic Garden and Royal Botanical Society of Belgium 10.5091/plecevo.190713 190713 Research Article Angiospermae Erythroxylaceae Nomenclature Systematics Taxonomy Africa Cameroon Nectaropetalum camerunense (Erythroxylaceae), a new species from the Sanaga basin in Cameroon, with a key to the genus Sonké Bonaventure bonaventure.sonke@ird.fr https://orcid.org/0000-0002-4310-3603 1 2 3 4 Simo-Droissart Murielle https://orcid.org/0000-0001-6707-8791 1 5 Bidault Ehoarn https://orcid.org/0000-0001-5029-8069 3 6 Ngoula Fernandez https://orcid.org/0009-0003-2614-6454 1 Lachenaud Olivier https://orcid.org/0000-0001-8972-4096 4 7 8 Plant Systematics and Ecology Laboratory, Higher Teachers’ Training College, University of Yaoundé I, Yaoundé, Cameroon Plant Systematics and Ecology Laboratory, Higher Teachers’ Training College, University of Yaoundé I Yaoundé Cameroon https://ror.org/022zbs961 International Joint Laboratory DYCOFAC, IRD-UYI-IRGM, Yaoundé, Cameroon International Joint Laboratory DYCOFAC, IRD-UYI-IRGM Yaoundé Cameroon Africa and Madagascar Department, Missouri Botanical Garden, Saint Louis, Missouri, United States of America Africa and Madagascar Department, Missouri Botanical Garden Saint Louis United States of America https://ror.org/04tzy5g14 Herbarium et Bibliothèque de Botanique africaine, Université Libre de Bruxelles, Brussels, Belgium Herbarium et Bibliothèque de Botanique africaine, Université Libre de Bruxelles Brussels Belgium https://ror.org/01r9htc13 AMAP Lab, IRD, CIRAD, CNRS, INRA, Université de Montpellier, Montpellier, France AMAP Lab, IRD, CIRAD, CNRS, INRA, Université de Montpellier Montpellier France https://ror.org/051escj72 Institut de Systématique, Évolution, et Biodiversité (ISYEB), Muséum National d’Histoire Naturelle, Centre National de la Recherche Scientifique, Sorbonne Université, École Pratique des Hautes Études, Université des Antilles, Paris, France Institut de Systématique, Évolution, et Biodiversité (ISYEB), Muséum National d’Histoire Naturelle, Centre National de la Recherche Scientifique, Sorbonne Université, École Pratique des Hautes Études, Université des Antilles Paris France https://ror.org/02ryfmr77 Meise Botanic Garden, Meise, Belgium Meise Botanic Garden Meise Belgium https://ror.org/01h1jbk91 Service Général de l’Enseignement supérieur et de la Recherche scientifique - Fédération Wallonie-Bruxelles, Brussels, Belgium Service Général de l’Enseignement supérieur et de la Recherche scientifique - Fédération Wallonie-Bruxelles Brussels Belgium https://ror.org/04q01pf08

Corresponding author: Bonaventure Sonké (bonaventure.sonke@ird.fr)

Academic editor: Elmar Robbrecht

 2026 19 08 2026 159 3 461 469 5403CED2-5655-5AF4-9C6C-35BC56A4A149 05 03 2026 17 04 2026 Bonaventure Sonké, Murielle Simo-Droissart, Ehoarn Bidault, Fernandez Ngoula, Olivier Lachenaud This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Background and aims – This paper describes and illustrates a new species of Nectaropetalum (Erythroxylaceae) from the Sanaga River basin in Cameroon. The genus otherwise includes eight species: two in the Democratic Republic of the Congo, five in coastal areas of eastern and southern Africa, and one in Madagascar.

Material and methods – The description of the new species is based on the study of 13 gatherings, field observations, and a comparison with available material of its congeners in BR and K. Its conservation status was assessed following the IUCN Red List Categories and Criteria.

Key results – The discovery is an important westwards range extension for the genus. Nectaropetalum camerunense sp. nov. most closely resembles N. acuminatum from Tanzania in vegetative characters, but differs by its shorter sepals and short thickened pedicels (vs sessile flowers). A key to the genus Nectaropetalum is presented. The new species is endemic to the middle Sanaga basin in Cameroon, where it occurs gregariously in periodically flooded riverine forests. It is assessed as Endangered following IUCN Red List Categories and Criteria. This brings the total number of Sanaga basin riverine endemics to date to nine, all of which are currently facing significant threats from agriculture and the construction of hydroelectric dams.

 Central Africa conservation IUCN Red List assessment riverine forests taxonomy threatened species Introduction

Cameroon’s forests are among the most biologically diverse in tropical Africa (Sosef et al. 2017). Since the 1990s, important botanical inventories have been conducted in the country, resulting in the publication of several conservation checklists (Cable and Cheek 1998; Cheek et al. 2000, 2004, 2010; Harvey et al. 2004; Onana and Cheek 2011; Onana et al. 2011). These inventories have led to the discovery of numerous new species in various families, including Annonaceae (Ghogue et al. 2017; Couvreur et al. 2022), Arecaceae (Mogue Kamga et al. 2018), Balsaminaceae (Janssens et al. 2015), Fabaceae (Sonké et al. 2024), Putranjivaceae (Quintanar et al. 2023), Orchidaceae (Droissart et al. 2009; Verlynde et al. 2013; Azandi et al. 2016), Sapotaceae (Nzoyeuem Djonko et al. 2025), and Rubiaceae (Taedoumg et al. 2017; Zemagho et al. 2017, 2018; Cheek et al. 2018; Lachenaud 2019; Lachenaud et al. 2020; Álvarez-Aguirre et al. 2021; Cheek and Sonké 2025). Further discoveries are undoubtedly forthcoming, which highlights the importance of conducting additional inventories in Cameroon, and more broadly, across Central Africa. Many of these taxonomic novelties are apparently endemic to the country and are currently facing threats from human activities, such as agriculture, logging, mining, and the construction of hydroelectric dams.

In 2021, a team of scientists from Institut de Recherche pour le Développement (IRD, France), the Plant Systematics and Ecology Laboratory (University of Yaoundé I), Biotope (an environmental consultancy based in France), and the Missouri Botanical Garden initiated an Environmental and Social Impact Assessment (ESIA) for a hydro-electric project at Kikot, along the Sanaga River. This study identified several taxonomic novelties, including the recently described Drypetes stevartii Sonké & Quintanar (Putranjivaceae; Quintanar et al. 2023), Talbotiella couteronii Sonké, M.Simo & Burgt (Fabaceae; Sonké et al. 2024), Synsepalum longiflorum Nzoyeuem, O.Lachenaud & Sonké (Sapotaceae; Nzoyeuem Djonko et al. 2025), Phragmanthera bidaultii Libalah & O.Lachenaud (Loranthaceae; Simo-Droissart et al. 2026), Tristicha spinulosa E.Bidault & Rutish. (Podostemaceae; Bidault et al. 2026), as well as a new species of Nectaropetalum Engl. (Erythroxylaceae), the focus of this article.

Erythroxylaceae are a pantropical family, comprising ca 270 species in four genera (Bittrich 2014; POWO 2026) that are easily distinguishable by the characters summarised in Table 1. Most species in this family belong to the highly diverse genus Erythroxylum P.Browne. Aneulophus Benth. and Pinacopodium Exell & Mendonça are both restricted to Central Africa and currently include two species each but are probably monospecific. The last genus, Nectaropetalum, so far consists of eight species. Five of these occur in the coastal areas of eastern and southern Africa (Verdcourt 1984), two in the Democratic Republic of the Congo (Bamps 1977), and one in Madagascar (Bardot-Vaucoulon 2001).

Key morphological characters and distribution of genera in Erythroxylaceae. Characters particular to one genus are highlighted in bold.

Aneulophus Erythroxylum Nectaropetalum Pinacopodium
Leaves opposite alternate alternate alternate
Stipules interpetiolar, caducous intrapetiolar, persistent (rarely caducous) intrapetiolar, caducous intrapetiolar, caducous
Inflorescences fasciculate fasciculate (or 1-flowered) fasciculate (or 1-flowered) cymose
Inner scale of petals absent well-developed, exceeding the sepals present but reduced, often hidden by the sepals (rarely absent) present but reduced, hidden by the sepals
Ovary 3(–4)-locular (2–)3-locular 2-locular 2-locular
Styles 3(–4), free (2–)3, free or connate at base 1, bilobed 1, bilobed
Fruits capsular, 3-valved drupaceous drupaceous ? (mature fruits not known)
Distribution Central Africa pantropical Central, Eastern & Southern Africa, Madagascar Central Africa

Nectaropetalum was originally classified in Linaceae (Engler 1902) but was soon transferred to Erythroxylaceae (Stapf 1909; Stapf and Boodle 1909), a position that was subsequently accepted by most authors (e.g. Marloth 1925; Gilbert 1958; Robson 1963; Verdcourt 1981, 1984), although some placed it, along with Pinacopodium, in a separate family Nectaropetalaceae (Exell and Mendonça 1951; Badré 1973). Phylogenetic studies strongly support the inclusion of Nectaropetalaceae within Erythroxylaceae, with Aneulophus being the sister lineage to the rest of the family (Schwarzbach and Ricklefs 2000; Sun et al. 2016). Schwarzbach and Ricklefs (2000) found Nectaropetalum and Pinacopodium as forming a clade sister to Erythroxylum, while Sun et al. (2016) found Nectaropetalum as sister to Erythroxylum (they did not include Pinacopodium in their study). As both studies included only one Nectaropetalum species, N. kaessneri Engl. and N. zuluense (Schönland) Corbishley respectively, the monophyly of the genus remains to be confirmed, particularly with regards to Pinacopodium. Although the latter genus’ cymose inflorescence is unique in the family, it is otherwise extremely similar to Nectaropetalum (where its type species was originally placed) in flower and leaf characters (Table 1). It seems quite plausible, therefore, that the two genera will have to be combined, with Nectaropetalum being the older name.

Apart from the relatively frequent East African N. kaessneri, most Nectaropetalum species are uncommon and rarely collected. None has yet been recorded from the Atlantic side of the African continent (e.g. Keay 1958; Badré 1972, 1973; Sosef et al. 2006; Onana 2011), so the discovery of the genus in Cameroon represents a significant expansion of its range to the west. The geographical gap between the Cameroonian species and its relatives will be partly bridged if Pinacopodium, which is found along the Atlantic coast from Gabon to Angola (Cabinda), proves to be congeneric. While the Cameroonian plant shows all the diagnostic characters of Nectaropetalum (Table 1), it differs from all its congeners and is therefore described here as a new species. We also present the first comprehensive key to the genus.

 Material and methods

The description of the new species, as well as information about its distribution, habitat, and phenology, is based on field work conducted in Cameroon and on the study of 13 herbarium gatherings (including spirit material), all of which were made by the authors and deposited in the following herbaria: BR, BRLU, K, M, MA, MO, P, WAG, and YA (herbarium codes according to Thiers 2026). Specimens of other Nectaropetalum species from BR and K were also studied for comparison. The descriptive terminology follows that used by Verdcourt (1984). The distribution map was made using QGIS v.3.40 (QGIS Development Team 2025) with the coordinate system set to WGS84/Pseudo-Mercator. Chorology follows White (1979). An assessment of the conservation status was made following the IUCN Red List Categories and Criteria (IUCN 2012; IUCN Standards and Petitions Committee 2024). The Extent of Occurrence (EOO) and Area of Occupancy (AOO) were calculated with GeoCAT (Bachman et al. 2011), using a 2 × 2 km grid.

 Taxonomic treatment Key to the species of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Nectaropetalum">Nectaropetalum</tp:taxon-name-part></tp:taxon-name></italic>

Note: As suggested by Verdcourt (1984), Nectaropetalum carvalhoi Engl. and N. kaessneri may be conspecific, but too little material of the former species has been studied to reach a definitive conclusion (despite it being the type of the genus).

1. Sepals imbricate, their margins widely overlapping; Madagascar Nectaropetalum eligulatum
– Sepals valvate, or sometimes very slightly imbricate in bud; continental Africa 2
2. Leaves obtuse to emarginate at apex; petals 7–28 mm long 3
– Leaves acuminate at apex; petals 2.5–12 mm long 4
3. Flowers borne in leaf axils or just below the leaves; petals 7–19 mm long; Somalia to Tanzania N. kaessneri
– Flowers borne at leafless nodes; petals 20–28 mm long; Mozambique N. carvalhoi
4. Stipules 10–23 mm long, leaving annular scars; flowers sessile or very shortly (≤ 1 mm long) pedicellate; South Africa N. capense
– Stipules ≤ 8 mm long, leaving interrupted scars; flowers sessile or with pedicel up to 10 mm long 5
5. Stipules bifid for around 1/3 of their length, leaving scars about half as wide as the twig; petals 2.5–4 mm long, with internal scale reaching around 1/3 of their length; D.R.Congo N. lebrunii
– Stipules not or very shortly bifid, leaving scars almost as wide as the twig (with only a narrow interruption on the side opposite the petiole); petals 6–12 mm long, with internal scale much shorter 6
6. Flowers and fruits on slender pedicels 5–10 mm long 7
– Flowers and fruits sessile or with short and thick pedicels up to 1 mm long 8
7. Leaf secondary veins strongly curved and distinctly more prominent than tertiary veins; young flower buds (still enclosed in the calyx) markedly 5-angled; D.R.Congo N. evrardii
– Leaf secondary veins almost straight and hardly more prominent than tertiary veins; young flower buds (still enclosed in the calyx) almost circular in section; South Africa, Kenya, Tanzania N. zuluense
8. Calyx lobes 2.2–2.5 mm long; flowers and fruits sessile; leaf blade 2.8–7 × 1–3 cm; Tanzania N. acuminatum
– Calyx lobes 1–1.5 mm long; flowers and fruits on short thick pedicel 0.5–1 mm long; leaf blade usually larger, 4–17 × 1.4–4.3 cm; Cameroon N. camerunense
Plantae Malpighiales Erythroxylaceae F41EB7B9-9B87-553D-8789-E4928BA6B076 Nectaropetalum camerunense urn:lsid:ipni.org:names:77394036-1 Sonké, M.Simo & O.Lachenaud sp. nov. Figs 1 , 2 , 3 ; Table 2 Type

CAMEROON • Central Region; Mbébé (Silobé); 4°07’45.41”N, 11°00’11.63”E; 28 Mar. 2025; fl.; Sonké & Ngoula 7959; holotype: BR [BR0000017787413]; isotypes: BR [BR0000017787406], BRLU [BRLU0045381, BRLU0045382, BRLU0045383], E, FR [FR-0038706], K, M, MA, MO, P, WAG, YA.

 Diagnosis

This species has acuminate leaves, and stipules leaving sub-annular scars with a narrow interruption on the side opposite the petiole, in which characters it resembles N. acuminatum Verdc.; it differs from the latter by its shorter calyx lobes, 1–1.5 mm long (vs 2.2–2.5 mm) and short thickened pedicels 0.5–1 mm long (vs pedicels absent).

 Description

Small tree or shrub up to 12 m tall, multi-stemmed; stems up to 12 cm in diameter. Twigs obliquely ascending, slightly flattened when young, then cylindrical, glabrous, soon covered with a pale grey-brown bark. Stipules 4.5–6.5 × 1–2 mm, intrapetiolar, narrowly triangular, folded lengthwise and initially forming a conical bud, entire or shortly (≤ 0.7 mm) bifid at apex and sometimes minutely fimbriate on the margins, with two dorsal keels, glabrous or with short sparse hairs on the keels, soon caducous and leaving sub-annular scars on the twigs (with an interruption on the side opposite the petiole). Leaves deciduous, appearing with the flowers, light green to burgundy when young, glabrous; petiole 4–6 mm long, 2-angled to slightly winged; blade 4–17 × 1.4–4.3 cm, oblong to elliptic, the base cuneate to obtuse, the apex gradually acuminate, thinly papyraceous, drying olive brown, or the lower side sometimes glaucous; midrib depressed on the upper side; secondary nerves 9–27 on each side, rather faint (only slightly more prominent than tertiary venation), forming irregular loops which anastomose 2–5 mm from the leaf margin; tertiary venation densely reticulate, forming areolae ca 0.5 mm in diameter, visible on both sides (both in fresh and dry state). Flowers axillary or sometimes borne at leafless nodes, solitary or in fascicles of up to 5, 5-merous, subtended by small, ovate to semi-circular bracts, 0.4–0.8 mm long, obtuse to rounded, fimbriate, persistent or caducous. Pedicel 0.5–1 mm long and thick, truncated-obconical, glabrous. Calyx lobes 5, almost free, 1–1.5 × 0.5–0.8 mm, triangular, acute, green, glabrous, valvate and completely enclosing the young bud. Petals 5, 8–10 × 2–3 mm, free, oblong, the apex rounded, white, glabrous, with a basal claw 1–1.5 mm long, and two internal scales, 0.3–0.8 mm long, triangular to semi-circular, borne just above the claw. Stamens 10, in a single whorl, the filaments alternately long (4–6 mm) and short (2.5–4 mm), united at base into a shallow cup 0.5–1 mm high, white; anthers 0.7–1.5 × 0.2–0.7 mm, oblong to elliptic, basifixed, dithecous, opening by longitudinal slits, brownish. Ovary 1.8–3 × 0.8–1 mm, 2–locular, with a single ovule per chamber, oblong, olive green, glabrous. Style 3–4.5 mm long, much longer than ovary, slightly shorter to slightly longer than stamens, linear, glabrous, the apex bilobed, the stigmas ca 0.5 mm long, elliptic, spreading to reflexed. Fruits 12–13 × 4–7 mm, fusiform to ovoid, the apex slightly beaked, yellowish green when fresh, grey-green after drying, with persistent calyx and stamens at base (the style sometimes persistent too). Seeds not seen.

 Distribution

Nectaropetalum camerunense is, based on current evidence, endemic to the middle Sanaga basin in Cameroon (Fig. 3); this area is part of the Lower Guinea subcentre of endemism of the Guineo-Congolian Region (White 1979).

 Habitat

The species occurs in riverine forest, 320–420 m a.s.l., on the banks of the Sanaga River and its tributary the Lobo River. These forests have a relatively low canopy (15–20 m tall), and an open undergrowth mainly consisting of Thunbergia sp., Psychotria leptophylla Hiern, and Rinorea dentata (P.Beauv.) Kuntze. Nectaropetalum camerunense is gregarious in this habitat (Fig. 1F); on a single transect of 200 × 5 m containing 183 trees with a diameter of at least 5 cm, it accounts for 9.8% of all individuals. The dominant tree species in this transect is Talbotiella couteronii, which is also gregarious (Sonké et al. 2024), and accounts for 24% of the individuals present. Other abundant tree species found in the forest are Albizia adianthifolia W.Wight, Canarium schweinfurthii Engl., Diospyros abyssinica (Hiern) F.White, Funtumia africana (Benth.) Stapf, Ongokea gore (Hua) Pierre, and Tessmannia africana Harms.

10.5091/plecevo.190713.figure1 8D69B81E-1995-5435-8B81-A56B44B0F0EA

Nectaropetalum camerunense. A. Apex of twig with young leaves and intrapetiolar stipules. B. Same, with leaves seen from the lower side. C. Same, with leaves seen from the upper side. D. Flowers and young leaves (note unequal stamen filaments). E. Twig with flower buds, one open flower, and old flowers. F. Habit. A, F from Sonké & Ngoula 7961; B, from Sonké & Ngoula 7965; C, D, E from Sonké & Ngoula 7959. Photos by Bonaventure Sonké.

https://binary.pensoft.net/fig/1744225 10.5091/plecevo.190713.figure2 06DBFD16-5D2B-5CA3-A465-7C9F22E93BE0

Nectaropetalum camerunenseA. Twig with fruit and flower buds. B. Fruit (note style at apex and stamens persistent at base). C. Leafless twig with flower buds and one fruit. D. Multi-stemmed base of the tree. A from Sonké & Yemdji 8027; B, C from Sonké & Yemdji 8026; D from Sonké & Ngoula 7965. Photos by Bonaventure Sonké.

https://binary.pensoft.net/fig/1744226 10.5091/plecevo.190713.figure3 9B03180C-5D31-58FB-959A-E01C0D95C69C

Distribution map of Nectaropetalum camerunense.

https://binary.pensoft.net/fig/1744227 Phenology

Flower buds appear in September, but the flowers open only in late March, at the start of the rainy season and when the leaves are sprouting. The flowering period is very short, lasting no more than two weeks. While most flowers in an inflorescence open at almost the same time, buds, open flowers, and withered flowers may occasionally be observed on the same branch (Fig. 1E). Fruits were collected in May, July, and November.

 Etymology

The species name was chosen since it is endemic to Cameroon, and the only species of Nectaropetalum occurring in the country.

 Preliminary IUCN conservation assessment

Nectaropetalum camerunense is known from 13 gatherings representing 12 unique occurrences and one or two subpopulations. Its extent of occurrence (EOO) is calculated as 35.6 km2, which falls within the limits of the Critically Endangered category under criterion B1. Its area of occupancy (AOO) is estimated as 12 km2, which falls within the limits for the Endangered category under criterion B2. Seven occurrences, which are located downstream of the Kikot hydroelectric dam project are threatened by shifting agriculture (one location). However, they are not expected to be affected by the dam project itself (not a regulating dam). No threats were identified to the four occurrences located at Ntol-Lébanga upstream of the dam project; these four occurrences represent one location. With regard to the most serious plausible threat, which is shifting agriculture, the 12 occurrences represent two locations, which falls within the limits of Endangered according to criterion B. We expect that shifting agriculture has led to a decline in habitat extent and quality and number of mature individuals, and will continue to do so in the future. For all these reasons, Nectaropetalum camerunense is assessed as Endangered: EN B1ab(iii,v)+2ab(iii,v).

 Notes

This species most closely resembles N. acuminatum, which is still only known from its type, collected in Tanzania. Although their ranges are separated by a gap of over 3,000 km, the two species are highly similar, and differ mostly in the size of their calyx lobes and pedicel development; additional differences in the style and ovary (Table 2) are of more uncertain value, since they might be related to the flower morph. Heterostyly is known to occur in other species of the genus (e.g. N. kaessneri) and there have been too few gatherings in bloom to date of either N. acuminatum or N. camerunense to determine whether their flowers are dimorphic; field observations will be necessary to solve this issue. It is not known whether there are any differences in the fruits, since those of N. acuminatum have never been collected.

Main morphological differences between Nectaropetalum acuminatum and N. camerunense.

N. acuminatum N. camerunense
Leaf blade size 2.8–7 × 1–3 cm 4–13 × 1.4–4 cm
Number of flowers per axil 1(2) 1 to 5
Pedicel absent short and thick, 0.5-1 mm
Calyx lobes (length) 2.2–2.5 mm, acuminate 1–1.5 mm, acute
Ovary 3–5 mm long, narrowly cylindrical 1.8–3 mm long, oblong
Style 2 mm, much shorter than ovary 3–4.5 mm, much longer than ovary

The other two species found in Central Africa, N. evrardii Bamps and N. lebrunii G.C.C.Gilbert, both restricted to the Democratic Republic of the Congo, are quite different from N. camerunense, mostly due to their long and slender pedicels; N. lebrunii also has much smaller petals with a more developed inner scale, and stipules markedly bifid (to about one third of their length).

The new species also resembles Pinacopodium congolense (S.Moore) Exell & Mendonça which, as discussed in the introduction, may well be congeneric. The latter has virtually identical leaves and stipules but is usually a taller tree with a single trunk, slender pedicels, and flowers arranged in cymose inflorescences; it occurs from Gabon to Angola (Cabinda) but not in Cameroon.

The stamen filaments of N. camerunense are distinctly unequal in length (alternately long and short) but this character is not or barely noticeable in herbarium specimens, since the longer filaments tend to curve more when dried, causing all the anthers to appear at almost the same level.

 Additional material examined

CAMEROON • Ntol-Lébanga, en amont du site du projet de construction du barrage de Kikot; 4°13’55.1”N, 11°07’56.19”E; 9 Jan. 2024; Nzoyeuem et al. 261; BRLU, K, MO, P, YA • Ntol-Lébanga, en amont du site du projet de construction du barrage de Kikot; 4°15’35.53”N, 11°07’2.15”E; 11 Jan. 2024; Relevé Cameroun 126; BRLU, MO, P, YA • Nkolmelen, Île de Ponis (Nord Lebanga); 4°15’31.14”N, 11°06’48.15”E; 30 Jul. 2023; Sonké 7481; BR, BRLU, K, M, MO, P, WAG, YA • Mbébé (Silobé); 4°07’43.24”N, 11°00’12.41”E; 23 May 2024; Sonké & Ngoula 7896; BR, BRLU, K, M, MO, P, YA • Mbébé (Silobé); 4°07’44.67”N, 11°00’11.97”E; 23 May 2024; Sonké & Ngoula 7897; BR, BRLU, K, MO, P, YA • Silobé (Mbébé); 4°07’46.24”N, 11°00’12.17”E; 1 Nov. 2024; Sonké & Atangana 7929; BR, BRLU, K, M, MO, P, YA • Mbébé (Silobé); 4°07’48.1”N, 11°00’10.89”E; 28 Mar. 2025; Sonké & Ngoula 7961; BR, BRLU, K, M, MO, P, WAG, YA • Mbébé (Silobé); 4°07’44.44”N, 11°00’12.46”E; 10 May 2025; Sonké & Ngoula 7965; BR, BRLU, MO, P, YA • Mbébé (Silobé); 4°07’44.87”N, 11°00’11.84”E; 21 Nov. 2025; Sonké & Yemdji 8026; BR, BRLU, FR, K, M, MO, P, YA • Mbébé (Silobé); 4°07’41.48”N, 11°00’3.46”E; 21 Nov. 2025; Sonké & Yemdji 8027; BR, BRLU, MO, P, YA • Mbebe, en aval du site du projet de construction du barrage hydroélectrique de Kikot; 4°07’42.2”N, 11°00’4.66”E; 21 Aug. 2023; Transect Cameroun 935; BRLU, YA • Ntol (île de Ponis), en amont du site du projet de construction du barrage hydroélectrique de Kikot; 4°14’27.66”N, 11°07’23.69”E; 31 Jul. 2023; Transect Cameroun 832; BRLU, YA.

 Discussion

Remarkably, this locally gregarious species has apparently never been collected before 2023, with no historical specimens found in herbaria to date. This is probably due to its restricted range and habitat. Indeed, riparian forests along the Sanaga were rarely explored by botanists until recently. As discussed in the introduction, several new species were discovered during the botanical inventories carried out for the environmental impact study of the Kikot hydroelectric dam project. Furthermore, Nectaropetalum camerunense, like Talbotiella couteronii which grows in the same habitat and flowers at the same time (Sonké et al. 2024), has a very short flowering period, and can easily remain unnoticed when it is not in flower.

The discovery of N. camerunense adds another species to the list of Sanaga Basin riverine endemics, which already includes Eugenia ancorifera Amshoff (Myrtaceae), Hibiscus elongatifolius Hochr. (Malvaceae), Maranthes sanagensis F.White (Chrysobalanaceae), Ostryocarpus zenkerianus Dunn (Fabaceae), Talbotiella couteronii (Fabaceae), Synsepalum longiflorum (Sapotaceae), Phragmanthera bidaultii (Loranthaceae), and Tristicha spinulosa (Podostemaceae). A new species of Turraea L. (Meliaceae), which is endemic to this area, is currently being described, and it is highly likely that more new species are awaiting to be discovered. Given the ongoing threats to their habitat, particularly from hydroelectric dams (three of which are already operating on the Sanaga, with another one under construction, and a further project at Kikot), there is an urgent need for further exploration and conservation measures.

 Acknowledgements

We thank the herbarium staff of BR, BRLU, K, P, and YA for their assistance while working in their institutes. Thanks are due to Dr Martin Cheek (Royal Botanic Gardens, Kew) for his assistance to the first author. Special thanks are due to Dr Jeannette Mapi-Sonké for various support and advice to the first and second authors. Field work by BS, MS-D, and FN was undertaken as part of an environmental impact assessment for the Kikot hydro-electric dam project. Kikot Hydro-Power Company and Electricité de France (namely Charles Bodel, Frederick Jacob, and Antoinette Kiboum) are warmly thanked for their support to our taxonomical studies, including in the field. We thank Dr Tariq Stévart (Missouri Botanical Garden), Dr Nicolas Granier and Xavier Rufray (Biotope) for their support. Numerous site visits to monitor phenology of the novelty have been funded by IRD through the International Joint Laboratory DYCOFAC project. We would also like to thank Désiré Ntamack for his help during field work and all other collectors of specimens of the new species.

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