Podostemaceae, a family of strictly aquatic plants found in rapids and waterfalls, include the single African species belonging to subfamily Tristichoideae, Tristicha trifaria (Bory ex Willd.) Spreng. While con­ducting an environmental impact assessment for the Kikot hydroelectric dam project on the Sanaga River in southern Cameroon, 208 Tristicha Thouars collec­tions were made, 93 of which exhibited peculiar mor­phological features that clearly distinguished them from T. trifaria and were found to represent a new species, T. spinulosa E. Bidault & Rutish., which is described. It differs from T. trifaria by having ovaries with only two locules, each with a single ovule (vs. many), two stigmas (vs. three), a capsule with a very thin wall that decays early (rather than a 3-valved dry capsule), and three tepals that surround the fruit and become scleri­fied during seed maturation to form spines. These mor­phological features, not previously observed in Tristicha, require an expansion of the morphological delimitation of the genus. The new species is endemic to the Sanaga River system; its conservation status is preliminarily assessed as Vulnerable because of threats resulting from hydroelectric and regulating dams, which have signifi­cantly increased submersion of most colonies in the Sanaga and Mbam rivers. The inclusion of a historical collection of T. spinulosa in a previous phylogeny reinforces the hypothesis that T. trifaria in Africa rep­resents multiple species. Further phylogenetic and mor­phological studies at the scale of tropical Africa are currently being undertaken by the authors.

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.

The genus Paramollugo Thulin ( Molluginaceae ) comprises herbs or small shrubs or subshrubs mainly distributed in the Madagascar region, but one species also widespread in the tropics and subtropics of the Old World, two restricted to the Caribbean and one to New Caledonia. In the revision presented here 11 species are recognized: P. decandra (Scott Elliot) Thulin, P. caespitosa (Scott Elliot) Thulin comb. nov., P. compressa Thulin sp. nov., P. simulans Sukhor. and P. elliotii Sukhor. endemic to Madagascar, P. nudicaulis (Lam.) Thulin in Madagascar and also widespread on neighbouring islands and in tropical and subtropical parts of Africa and Asia, P. angustifolia (M.G. Gilbert & Thulin) Thulin in Madagascar and Somalia, P. digyna (Montrouz.) Sukhor. endemic to New Caledonia, P. nesophila Thulin et al. sp. nov. endemic to & Icirc;les & Eacute;parses (Scattered Islands) in the Mozambique Channel, P. spathulata (Sw.) Sukhor. widespread in the Caribbean, and P. cuneifolia (Griseb.) Thulin endemic to Cuba. For each species descriptions and discussions are provided, as well as illustrations and distribution maps. New lectotypes are designated for Mollugo caespitosa Scott Elliot and M. digyna Montrouz. The phylogeny of the genus is reconstructed based on plastid trnK-matK and nuclear ITS sequences. Conflict between the datasets is seen as a result of the genus probably being a polyploid complex. Dating of the phylogeny resulted in two alternative topologies, both estimating the age of the stem clade to the Eocene, with a presumed origin in Africa, and mid-Miocene as the age of the crown clade, with a presumed origin in Madagascar and/or the Caribbean. The age of the crown clade is also the estimated date for a split between a Caribbean clade and the rest of the genus, long distance dispersal from Madagascar to the Greater Antilles being the most likely explanation.

Background and aims – For some time now, the forests of the Sanaga basin in Cameroon have been threatened by the construction of numerous hydroelectric dams. In anticipation to this construction work, botanical surveys were carried out, resulting in the discovery of many species new to science. One of these certainly belongs to the genus Talbotiella in Leguminosae. Material and methods – This study is based on morphological observations on herbarium specimens, through detailed examination of 28 specimens of the new tree species as well as specimens of existing species of Talbotiella. Key results – Talbotiella couteronii is described and illustrated. The new species resembles Talbotiella batesii but has fewer leaflets, 5–10 pairs; an inflorescence usually with fewer flowers, 5–12; and flowers with longer pedicels, 10–20 mm long. Talbotiella couteronii is endemic to Cameroon, where it is restricted to the middle Sanaga basin in the Central Region and the Littoral Region. It occurs gregariously in periodically flooded riverine forests. Talbotiella couteronii is preliminarily assessed as Endangered following the IUCN Red List categories and criteria. The genus Talbotiella now consists of 10 species; of which six species are endemic to Cameroon. A comparative table summarizes the main vegetative characteristics of the 10 species. This treatment also includes an update of the description of T. bakossiensis.

Convolvulaceae is a diverse and economically important plant family in Tropical Africa, including the crop sweet potato ( Ipomoea batatas (L.) Lam.) and its wild relatives, morning glories ( Ipomoea L.), bindweeds ( Convolvulus L.), invasive weeds (e.g. Cuscuta L.) and several other species with food, medicinal, or traditional uses. A taxonomic treatment of Convolvulaceae for Guinea is here presented, including comprehensive morphological descriptions, identification keys to genera and species, distribution and ecological information, specimen data, and documentation of known uses. A total of 51 species belonging to 16 genera are documented, 38 of which are native, and 13 presumed introduced; 33 of these are used as medicine, 18 as ornamental, 12 as food and 15 with a range of other uses. Preliminary IUCN Red List assessments were carried out for 45 species for which there were no previous assessments All 45 preliminary conservation assessments were categorised as Least Concern for the global Red List, with 61% of native species having at least one occurrence point falling within protected areas. ### Competing Interest Statement The authors have declared no competing interest.

The fern genus Didymoglossum (Hymenophyllaceae) is not so diverse in Africa with seven species at most. However, its local taxonomy is surprisingly still strongly debated, in particular within the Didymoglossum erosum complex interpreted either as a single polymorphic species or as a group of at least three distinct but morphologically very close taxa ( D. erosum , Didymoglossum chamaedrys , and Didymoglossum benlii ). Investigating these taxonomic issues and more generally the diversity of the genus in Africa and its origin, we conducted a complete anatomo–morphological analysis coupled with a molecular phylogenetic work based on rbcL . Our results support the recognition of all seven species, including Didymoglossum robinsonii that is likely distinct from the Neotropical Didymoglossum reptans to which the African populations were traditionally attributed. We here propose new characters and a novel key to distinguish the seven African species which also include Didymoglossum ballardianum , Didymoglossum lenormandii , and Didymoglossum liberiense . Once the taxonomy is clarified with respect to the distinct evolutionary lineages evidenced, the biogeographic history of the genus in Africa is discussed based on a divergence time estimation and the reconstruction of the ancestral geographic areas. These analyses reveal a Mesozoic (Cretaceous) vicariance event within Didymoglossum which is the second one hypothesized for the family Hymenophyllaceae.

The Checklist of the Vascular Plants of the Republic of Guinea (CVPRG) is a specimen-based, expert-validated knowledge product, which provides a concise synthesis and overview of current knowledge on 3901 vascular plant species documented from Guinea (Conakry), West Africa, including their accepted names and synonyms, as well as their distribution and status within Guinea (indigenous or introduced, endemic or not). The CVPRG is generated automatically from the Guinea Collections Database and the Guinea Names Backbone Database, both developed and maintained at the Royal Botanic Gardens, Kew, in collaboration with the staff of the National Herbarium of Guinea. A total of 3505 indigenous vascular plant species are reported of which 3328 are flowering plants (angiosperms); this represents a 26% increase in known indigenous angiosperms since the last floristic overview. Intended as a reference for scientists documenting the diversity and distribution of the Guinea flora, the CVPRG will also inform those seeking to safeguard the rich plant diversity of Guinea and the societal, ecological and economic benefits accruing from these biological resources.

Background and aims – Within angiosperms, vivipary has been reported in less than 0.1% of all species. We herein report the first occurrence of vivipary in an Afrotropical Melastomataceae and discuss its phylogenetic position, habit, habitat, and fruit attributes. Material and methods – Observational data were gathered from a field expedition to Gabon, and from herbarium specimens from BR, BRLU, P, and WAG. A phylogeny was generated to map all the eight species exhibiting vivipary in Melastomataceae. Key results – Amphiblemma ciliatum is currently the only known melastome species in the Afrotropics exhibiting vivipary. It is likely that its angular capsules depend on rainwater for seed dispersal. Conclusion – The combination of a herbaceous habit and angular fruits with the occurrence on shaded humid tropical rainforest floor during periods of incessant rainfall and high humidity might be responsible for vivipary in most Melastomataceae.

Background and aims – Podostemaceae is a family of strictly aquatic plants found in rapids and waterfalls. Despite a recent treatment in the Flore du Gabon, the family remained poorly known, with no major studies including Gabonese collections, and almost no targeted inventories since 1966. We present the first large-scale inventory of this family in Gabon, targeting Podostemaceae throughout the country, providing new additions to the flora of Gabon and many new records of poorly known species. Material and methods – Fieldwork was conducted in Gabon between 2017 and 2021. The collected specimens were primarily preserved in ethanol with associated silica gel-preserved material and photographs. Material available at BR, BRLU, LBV, MO, P, WAG, and Z/ZT was examined. For each species, information on distribution and ecology is presented, as well as a distribution map in Gabon. Key results – The 500 newly collected specimens represent 91.4% of all known collections of Podostemaceae from Gabon. Three taxa are newly recorded for the country, including one genus (Inversodicraea tenax, Ledermanniella schlechteri, and Saxicolella nana). New distribution records are also presented for 13 little-known species. Four taxa are excluded from the Gabonese flora (the genus Dicraeanthus, Inversodicraea ledermannii, Ledermanniella sanagaensis, and Macropodiella garrettii). To date, 20 species belonging to five different genera are known to occur in Gabon. A new combination is proposed for Ledermanniella nicolasii, and Inversodicraea tanzaniensis is now considered as a synonym of Inversodicraea tenax.

A study of the genus Erythroxylum P.Browne from the Comoros archipelago reveals two new species, E. choungiense E.Bidault, Traclet & M.Pignal, sp. nov. from Mayotte and E. labatii E.Bidault & M.Pignal, sp. nov. from Mwali and Ngazidja, both of which are described and illustrated. The distribution of a third species, E. elegans Baill., is now only known with certainty to include Mayotte and Nzwani, and possibly Ngazidja, following the exclusion of material now assigned to the new species. A risk of extinction assessment using the IUCN Red List criteria is provided for the new taxa and the morphological features that distinguish them from their apparently close relative are summarized. A key to the species of Erythroxylum in the Comoros is provided in both English and French. Erythroxylum choungiense sp. nov. is endemic to Mount Choungi, and its conservation status is assessed as Critically Endangered. Mount Choungi harbors the unique patch of hygrophilous submontane shrubland in Mayotte, to which at least five species are now known to be strictly endemic: Cassipoureaovata Tul., Eugenia choungiensis Byng & N.Snow, Psiadia pascalii Labat & Beentje, Syzygium labatii Byng & N.Snow, and Erythroxylum choungiense sp. nov.. Erythroxylum labatii sp. nov. is only known from the submontane forests on ridges and steep slopes on Moheli and Ngazidja, at an elevation of 600 to 1300 m a.s.l., and is assessed as Endangered.

Background and aims – The genus Englerodendron (Leguminosae-Detarioideae) has recently been enlarged to include Isomacrolobium and Pseudomacrolobium, and currently includes 18 tropical African species. The recent discovery of a new species in Gabon has led us to re-evaluate the delimitation of several taxa in the genus.Material and methods – This paper is based on field work by the authors in Gabon, and on a study of herbarium material from BR, BRLU, K, LBV, MO, P, and WAG; normal practices of herbarium taxonomy have been applied.Results – Englerodendron nguemae is described and illustrated as a new species, endemic to Gabon. It is remarkable for the variation in its leaves, which may be 2-jugate, 1-jugate, or unifoliolate on the same plant. The species is most similar to E. brachyrhachis, but the latter has uniformly 2-jugate leaves; E. nguemae also differs in its longer and more broadly winged leaf rachis (if present) that is convex (not flat) above, its stamen filaments pubescent at the base, and its glabrous style. Several collections from the Democratic Republic of the Congo, previously associated with E. obanense, are considered here to represent two different taxa. One of them, E. macranthum (a new combination and name at new rank based on Macrolobium isopetalum var. macranthum, which is raised to species status), is endemic to the Mayombe range and differs from E. obanense by its inflorescences branched from the base or nearly so, and its shorter 1-seeded pods. The other taxon, still imperfectly known and here treated as Englerodendron sp. A, is endemic to the Kivu region; it differs from E. obanense by its large foliaceous stipules and from E. conchyliophorum by the lack of a basal auricle on the stipules. In addition, the first records of E. leptorrhachis from Equatorial Guinea, and of E. conchyliophorum from the Republic of the Congo, are documented, and a revised key to the now 21 species (one undescribed) of Englerodendron is presented.

Endemism is one of the most important concepts in biogeography and is often used to guide biodiversity conservation, yet our understanding of the determinants of endemism in many biodiverse tropical regions is limited. This is true for western Central Africa, a region with one of the highest levels of plant diversity in tropical Africa, where endemism is poorly documented. This study examines the Gabonese Area of Endemism (GAE) and explores the main characteristics and determinants of its vascular plant endemism with regard to taxonomy, growth form, habitat, distribution, and range size. We compiled a comprehensive, verified specimen database of vascular plant taxa restricted to the GAE, comprising 19,876 occurrences of 1145 species and infraspecific taxa, and we characterized the habitat and habit for each taxon. We then calculated the proportion of taxa in the regional flora that are endemic to the GAE. A Wilcoxon rank-sum test was used to investigate range size among endemic taxa exhibiting different growth forms, and Fisher exact tests were used to explore the association between their habit and habitat, and to test the distribution of these attributes among higher-level taxa and growth forms compared to patterns in the regional flora as a whole. We found that endemic taxa represent ca. 13% of the GAE flora, and that the rate of endemism varies considerably among taxonomic groups and growth forms. Endemism is highest among shrubs (22%) and lowest in herbs (8%), especially monocotyledons (e.g., 5% among Poales). Most endemic taxa grow preferentially in forest habitats, the dominant vegetation type of the region. Endemic trees, which structure forest ecosystems, have significantly larger ranges than endemic herbs, climbers, and shrubs. About 17% of the flora of Gabon is endemic or subendemic to the country. Our results show that the dispersal capacity of taxa and the biogeographical history of the region appear to be critical factors in explaining differences in the rate of endemism among growth forms and taxonomic groups. Our findings also highlight the benefits of carefully building a comprehensive and verified database for studying rare and range-restricted plants, and they underscore the necessity to strengthen botanical exploration throughout western Central Africa in order to develop improved and better-informed conservation strategies.

The High Conservation Value (HCV) concept, developed by the Forest Stewardship Council to promote sustainable forest management, is widely employed for certification of forestry and agriculture concessions, and has been adopted by many logging and palm oil companies. HCV criterion 1, which deals with "endemic, and rare, threatened or endangered species", is rarely used in certification, mainly because lists of these species are incomplete, especially for plants, and performing threat assessments is time-consuming. The IUCN Red List Categories are often suggested as a suitable basis to define threatened taxa for the application of HCV1, but this requires the rapid and efficient assessment of large numbers of species. Using the plants endemic to Gabon as a case study, we propose a rapid, two-step procedure to identify HCV1 species. First, based on 3,298 verified and geo-referenced herbarium records, we used GIS layers and an automated computational workflow in the R environment to identify potentially threatened species using an approach aligned with IUCN Red List criteria A, B, and D. Ninety percent of the automated assessments correctly indicated the risk of extinction; errors involved incorrect assessments of species whose habitat is in reality not threatened, or occurred during the calculation of the number of locations (sensu IUCN) when a single threat impacts large areas. In a second step designed to correct these issues and comply with the Red List guidelines, we performed species-by-species verification of the automated assessments, taking into account the ecology and habitat of each species and the nature of the threats it faces. Of the 389 endemic taxa analyzed, 86 % were identified as threatened (83 CR, 171 EN, and 80 VU); of these, only 35 % are recorded from at least one National Park, but most are found in logging/oil palm (72 %) or mining (55 %) concessions, underscoring the need to improve the application of the HCV concept. To strengthen the use of HVC subcriterion 1.2 (rare, threatened or endangered species), we propose an explicit method for identifying rare species based on a quantitative threshold of the Extent of Occurrence (20,000 km²), and we examine the concept of endemicity with respect to the application of HVC subcriterion 1.3 (endemic species). The proposed methodology addresses an urgent need to develop a national interpretation of the HCV concept in Gabon, adopted as a national standard for logging concessions, and offers an efficient, reliable approach for the application of HVC1 elsewhere in Central Africa.

A systematic survey of lichens was performed in 2019 in four of the five territories constituting the French Scattered Islands (Europa Island, Juan de Nova, Glorioso Islands, and Tromelin) focusing on the genus Ramalina. Species were characterized using morphological (macroscopic and microscopic) features and an accurate chemical profiling method based on high-performance liquid chromatography coupled with diode-array detection and electrospray ionization tandem mass spectrometry (HPLC-DAD-MS). Five species were found in these territories. Two of them, Ramalina dumeticola and R. ovalis, are already known. Three species are introduced here as new to science: Ramalina gloriosensis sp. nov., R. hivertiana sp. nov., and R. marteaui sp. nov. An identification key is provided for the species found in the area and morphologically closely related taxa.

Over the last several years, the IUCN Red List approach for assessing the risk of extinction faced by species has been adapted into a Red List of Ecosystems methodology. This endeavor faces several important challenges, including how to define the types of ecosystems to which the Red List criteria are applied, and how to manage information on the geographic distribution of ecosystems in an open, transparent, and standardized manner linking mapping, typology, and field studies. We propose a fundamentally novel approach that differs from currently available ecosystem typologies in three important aspects by (1) offering a new way of conceptualizing types of ecosystems, (2) providing an explicit method for communicating the conceptualized ecosystems and how they are circumscribed, and (3) developing technical tools for managing the resulting conceptual model. Firstly, ecosystem types are defined by studying biogeoclimatic gradients using an approach that is both modular (in which combinations of ecological factors are studied at a given scale) and hierarchical (involving relative spatial and temporal scales in which local/site gradients are dependent on bioclimatic/regional gradients). This avoids the problem of classes that are not mutually exclusive and enables the classification of all types of ecosystems, including for example marshes on rocky outcrops in superhumid tropical montane areas. Secondly, the names of ecosystem species are linked to a nomenclatural type defined by a 'type site' or 'biotype', adopting a principle that makes clear a given author's notion of an ecosystem type even if the accompanying name and description are partial or imperfect, or when the ecosystem type is delimited too broadly according to the interpretation of another author. Ecosystem names are structured as a descriptive diagnosis based on a standardized set of characters and character states. This typological approach for facilitating the naming and comparison of ecosystem circumscriptions is thus truly taxonomic in nature. Thirdly, in order to facilitate the use and application of the conceptual approach presented here, we translate it into a practical tool by developing a smartphone-based system to collect data for observing and describing virtual ecosystem specimens in the field, along with the "Bio" database, which manages ecosystem data and also enables tracking synonymies using an open system that entails assigning determinavits to biotypes.

A review of the taxonomy of Palisota Rchb. ex Endl. (Commelinaceae) in Atlantic Central Africa, as a precursor to preparing a treatment of Commelinaceae for the Flore du Gabon, results in the description of eight new species: Palisota akouangoui E. Bidault & Burg, Palisota alboanthera Burg & E. Bidault, Palisota cristalensis E. Bidault & Burg, Palisota fadenii Burg & E. Bidault, Palisota leewhitei Burg, O. Lachenaud & E. Bidault, Palisota plicata E. Bidault & Burg, Palisota repens E.Bidault & Burg, and Palisota stevartii Burg & E. Bidault. A discussion is provided on the relevance of several morphological characters and on the taxonomy and delimitation of two poorly known species, Palisota bogneri Brenan and Palisota satabiei Brenan. The new species are described and illustrated with line drawings and field photographs, accompanied by a distribution map. A key to the Palisota species in Atlantic Central Africa is provided. Preliminary risk of extinction assessments indicate that three of them are "Endangered", three are "Vulnerable", one is "Near Threatened", and one species is "Least Concern". Thirty-two species are currently recognized in Palisota, nineteen of which occur in Gabon.

Background – The number of vascular plant species known to occur in Gabon rises quickly due to renewed collecting and inventory activities, often in little-known or previously uncollected areas.Methods – Herbarium material from BR, BRLU and WAG was studied.Results – Two genera (Alloteropsis, Entolasia), eleven species and one variety of grasses are recorded from Gabon for the first time (Alloteropsis paniculata, Cenchrus echinatus, Elionurus platypus, Entolasia olivacea, Eragrostis patens, Hyparrhenia diplandra var. mutica, Leersia triandra, Loudetia annua, Oryza longistaminata, Rottboellia purpurascens, Sacciolepis africana and Setaria geminata), while information on two erroneous species reports is provided. This brings the total number of grass species known to occur in Gabon to 190. Finally, new records of four rare species (Elionurus hensii, Guaduella macrostachys, Paratheria prostrata and Puelia schumanniana) are discussed.