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International audience; Plant species providing Non-Timber Forest Products (NTFP) are economically important across Africa. How this heterogeneous and understudied resource will respond to ongoing climate change remains understudied. Here, we modelled the impact of end-of-the-century climate change on the distribution of 40 NTFP plant species distributed across tropical Africa. Occurrence data were extracted from a taxonomically verified database and three different ecological niche modelling algorithms were used. Species distributions were modelled under two end-of-century (2085) climate change models (RCP4.5 and RCP8.5) and two dispersal scenarios (limited and expanded). We show that for the 40 NTFP plant species studied here, different responses are modelled with some species gaining in suitable habitats (47.5%–65% under RCP4.5), whereas others will lose in suitable habitats (35%–52.5% under RCP4.5). Nevertheless, we also show that our results vary between the different methods used, such as modelling algorithms, dispersal scenarios and general circulation models. Overall, our results suggest that the response of NTFP species to climate change depends on their distribution, ecology and dispersal ability.

International audience; Aim: Examining tree species-environment association can offer insight into the drivers of vegetation patterns and key information of practical relevance to forest management. Here, we aim to quantify the contribution of climate and soil gradients to variation in Central African tree species composition (abundance and occurrence). Location: Tropical rainforests of southern and eastern Cameroon. Methods: We established 82 1-ha permanent plots across seven localities and censused all trees ≥ 10 cm in diameter, representing a total of 37,733 trees and 455 species. In 60 of those plots, we measured ten soil variables describing texture and nutrients levels and extracted ten bioclimatic variables from global-gridded climate databases. We synthesized the main environmental gradients by conducting principal component analyses on climate and soil data respectively. We performed unconstrained and constrained non-symmetric correspondence analyses to account for the individual and joint contributions of climate and soil on species abundance and occurrence. Results: Climate and soil contributed similarly to variances of species abundance and occurrence (12–15 % variance for climate vs. 11–12 % variance for soil). Climate influence mostly concerns some abundant species, while some of the less abundant species were mainly driven by soil. Fractions of species variances accounted for by climate and soil show strong correlation when assessed from species occurrence and abundance data. Conclusion: Variation in occurrence and abundance of tropical forest trees can be partly shaped by both climate and soil gradients in Cameroon, which emphasizes the importance to jointly consider soil and climate in species distribution modeling. Less abundant species may express environmental influence differently than abundant species and convey complementary information about community assemblage. Though showing congruent patterns here, species abundance and occurrence reflect different interacting community processes and both should be examined to better understand vegetation patterns.

The oceanic islands of the Gulf of Guinea display a large diversity of environmental conditions and biological communities, whose interactions have contributed to the development of a great variety of ecosystems, from mangroves to montane grasslands. Human activities have extensively and profoundly altered many of these natural ecosystems over the past five centuries. We review key studies to propose an updated classification map of terrestrial ecosystems, taking advantage of up-to-date spatial information on abiotic gradients and biological distributions. To guide future research and conservation programs, we highlight challenges and pending questions regarding our understanding of the structure, integrity, and dynamics of terrestrial ecosystems in these islands.

Despite a long history of botanical collecting in the three oceanic islands of the Gulf of Guinea, no recent studies have documented floristic patterns. This chapter summarizes information on the vascular plants of the islands, including inventories conducted on Príncipe and São Tomé since 2017, as well as two recent expeditions to Annobón. An updated database of the vascular flora was compiled, which includes 14,376 records representing 1285 species and infraspecific taxa (1028 native). Príncipe has 445 species and infraspecific taxa (394 native), São Tomé has 1044 (842 native), and Annobón has 344 (274 native). Recent inventory work has generated collections of more than 90% of the endemic woody species. Several very rare taxa were rediscovered, includingBalthasaria mannii(Oliv.) Verdc., 1969 (Pentaphylacaceae) andPsychotria exelliiR. Alves, Figueiredo and A.P. Davis, 2005 (Rubiaceae), neither of which had been seen for more than 50 years. At least 17 species new to science were also discovered on Príncipe and São Tomé. Of the 1028 indigenous taxa, 164 (16%) are currently considered endemic to the islands. Of the 285 species evaluated according to the IUCN Red List criteria, 2 (0.7%) were Data Deficient, 226 (79.3%) Least Concern or Near Threatened, 55 (19.3%) threatened (including 3 Critically Endangered, 21 Endangered, and 31 Vulnerable), and 2 (0.7%) Extinct. On São Tomé and Príncipe, 325 plant species are used in traditional medicine, 37 of which are endemic. These results should be used to identify new priority sites for conservation, including on Annobón, where priority sites are less well defined.

International audience; 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.

Africa is forecasted to experience large and rapid climate change1 and population growth2 during the twenty-first century, which threatens the world’s second largest rainforest. Protecting and sustainably managing these African forests requires an increased understanding of their compositional heterogeneity, the environmental drivers of forest composition and their vulnerability to ongoing changes. Here, using a very large dataset of 6 million trees in more than 180,000 field plots, we jointly model the distribution in abundance of the most dominant tree taxa in central Africa, and produce continuous maps of the floristic and functional composition of central African forests. Our results show that the uncertainty in taxon-specific distributions averages out at the community level, and reveal highly deterministic assemblages. We uncover contrasting floristic and functional compositions across climates, soil types and anthropogenic gradients, with functional convergence among types of forest that are floristically dissimilar. Combining these spatial predictions with scenarios of climatic and anthropogenic global change suggests a high vulnerability of the northern and southern forest margins, the Atlantic forests and most forests in the Democratic Republic of the Congo, where both climate and anthropogenic threats are expected to increase sharply by 2085. These results constitute key quantitative benchmarks for scientists and policymakers to shape transnational conservation and management strategies that aim to provide a sustainable future for central African forests. A large dataset of 6 million trees from 193 taxa is used to map the floristic and functional composition of central African forests and predict their vulnerability to climate change.

Phylogenies are a central and indispensable tool for evolutionary and ecological research. Even though most angiosperm families are well investigated from a phylogenetic point of view, there are far less possibilities to carry out large-scale meta-analyses at order level or higher. Here, we reconstructed a large-scale dated phylogeny including nearly 1/8th of all angiosperm species, based on two plastid barcoding genes, matK (incl. trnK) and rbcL. Novel sequences were generated for several species, while the rest of the data were mined from GenBank. The resulting tree was dated using 56 angiosperm fossils as calibration points. The resulting megaphylogeny is one of the largest dated phylogenetic tree of angiosperms yet, consisting of 36,101 sampled species, representing 8,399 genera, 426 families and all orders. This novel framework will be useful for investigating different broad scale research questions in ecological and evolutionary biology., info:eu-repo/semantics/published

Paleo-environmental data show that the distribution of African rain forests was affected by Quaternary climate changes. In particular, the Dahomey Gap (DG) – a 200 km wide savanna corridor currently separating the West African and Central African rain forest blocks and containing relict rain forest fragments – was forested during the mid-Holocene and possibly during previous interglacial periods, whereas it was dominated by open vegetation (savanna) during glacial periods. Genetic signatures of past population fragmentation and demographic changes have been found in some African forest plant species using nuclear markers, but such events appear not to have been synchronous or shared across species. To better understand the colonization history of the DG by rain forest trees through seed dispersal, the plastid genomes of two widespread African forest legume trees, Anthonotha macrophylla and Distemonanthus benthamianus, were sequenced in 47 individuals for each species, providing unprecedented phylogenetic resolution of their maternal lineages (857 and 115 SNPs, respectively). Both species exhibit distinct lineages separating three regions: 1. Upper Guinea (UG, i.e. the West African forest block), 2. the area ranging from the DG to the Cameroon volcanic line (CVL), and 3. Lower Guinea (LG, the western part of the Central African forest block) where three lineages co-occur. In both species, the DG populations (including southern Nigeria west of Cross River) exhibit much lower genetic diversity than UG and LG populations, and their plastid lineages originate from the CVL, confirming the role of the CVL as an ancient forest refuge. Despite the similar phylogeographic structures displayed by A. macrophylla and D. benthamianus, molecular dating indicates very contrasting ages of lineage divergence (UG diverged from LG since c. 7 Ma and 0.7 Ma, respectively) and DG colonization (probably following the Mid Pleistocene Transition and the Last Glacial Maximum, respectively). The stability of forest refuge areas and repeated similar forest shrinking/expanding events during successive glacial periods might explain why similar phylogeographic patterns can be generated over contrasting timescales.

Aim: To delineate bioregions in tropical Africa and determine whether different plant growth forms (trees, terrestrial herbs, lianas and shrubs) display the same pattern of regionalization, diversity and endemism as the whole flora.Location: Tropical Africa (excl. Madagascar), from 20 degrees N to 25 degrees S.Taxon: Vascular plants.Methods: Analyses were based on occurrences of 24,719 vascular plant species distributed across tropical Africa extracted from the RAINBIO database. The majority of species (93%) were classified into four growth forms: terrestrial herbs, trees, shrubs and lianas. Biogeographical regions (bioregions) were delimited using a bipartite network clustering approach on the whole dataset and then separately for each growth form. Relationships among bioregions were investigated using non-metric multidimensional scaling ordination, flora nestedness and endemism patterns.Results: Analyses of the whole dataset identified 16 bioregions and 11 transition zones. These were congruent with most of the currently recognized phytogeographical classifications, and also highlighted previously under-recognized bioregions. Bioregion endemism rates were lower and species richness higher when compared to estimates from the White/Association pour l'Etude Taxonomique de la Flore d'Afrique Tropicale (AETFAT) classification. Analysed separately, plant growth forms showed contrasting geographical patterns. Bioregionalization was better resolved for closed forest types using trees and lianas and for open vegetation types using terrestrial herbs, while shrubs showed good discriminative power in all vegetation types.Main conclusions: We show that distribution patterns based on solely trees are not sufficient to define floristic bioregions in tropical Africa. Analyses of spatial patterns using different growth forms are complementary, likely reflecting different evolutionary processes and ecological relationships. The contribution of growth forms to delimit geographical floristic patterns across tropical Africa is of critical importance for land use planning and management, and for selecting priority conservation areas.

Combining genetic and morphological markers is a powerful approach for species delimitation, much needed in tropical species complexes. Greenwayodendron (Annonaceae) is a widespread genus of trees distributed from West to East African rainforests. Two species and four infra-specific taxa are currently recognized. However, preliminary genetic studies and morphological observations suggested the occurrence of additional species, undescribed to date. We tested species delimitation within Greenwayodendron by combining morphological and population genetics data. First, a visual inspection of about a thousand specimens suggested the existence of seven morphogroups: four of them occur in Central Africa and overlap in Gabon while three others are allopatric, occurring respectively in West Africa, East Africa, and the islands of São Tomé and Príncipe. Their morphological differentiation was confirmed by analysis of 27 morphological characters coded from 233 herbarium specimens. Second, after genotyping 800 samples at eight nuclear microsatellites, Bayesian clustering analyses (STRUCTURE) identified four genetic clusters corresponding to the well-sampled morphogroups but failed to separate the three remaining morphogroups represented by few samples. However, we show that this is an inherent limit of the STRUCTURE algorithm, whereas factorial correspondence analysis (FCA) and pairwise FST and RST measures confirmed the genetic differentiation of all morphogroups. We considered that a clear genetic differentiation occurring between sympatric populations advocates for recognizing distinct species following the biological species concept. Our analyses highlight that the current taxonomic treatment of Greenwayodendron underestimates the total number of species. We identified two new species and support separation at the rank of species of two varieties (G. suaveolens subsp. suaveolens var. gabonica, G. suaveolens subsp. suaveolens var. suaveolens) and one subspecies (G. suaveolens subsp. usambaricum). The taxonomic status of specimens collected in São Tomé and Príncipe remains inconclusive, partly due to the limited fertile material available. Our study highlights the strength of combining morphological and population genetics data for discovering new taxa. Guidelines for using genetic clustering approaches in species delimitation are provided., SCOPUS: ar.j, info:eu-repo/semantics/published

Preserving tropical biodiversity is an urgent challenge when faced with the growing needs of countries. Despite their crucial importance for terrestrial ecosystems, most tropical plant species lack extinction risk assessments, limiting our ability to identify conservation priorities. Using a novel approach aligned with IUCN Red List criteria, we conducted a continental-scale preliminary conservation assessment of 22,036 vascular plant species in tropical Africa. Our results underline the high level of extinction risk of the tropical African flora. Thirty-three percent of the species are potentially threatened with extinction, and another third of species are likely rare, potentially becoming threatened in the near future. Four regions are highlighted with a high proportion (>40%) of potentially threatened species: Ethiopia, West Africa, central Tanzania, and southern Democratic Republic of the Congo. Our approach represents a first step toward data-driven conservation assessments applicable at continental scales providing crucial information for sustainable economic development prioritization., SCOPUS: ar.j, info:eu-repo/semantics/published

International audience; Background and aims – The rapid expansion of human activities in South Cameroon, particularly mining in mountainous areas, threatens this region’s exceptional biodiversity. To comprehend the effects of land-use change on plant diversity and identify conservation priorities, we aim at providing a first comprehensive plant checklist of the Ngovayang Massif, focusing on the two richest plant families, Orchidaceae and Rubiaceae.Location – The Ngovayang Massif Area (NMA) is located in the South Region of Cameroon. It is covered by lowland and submontane rainforest (100 to 1110 m elevation).Methods – We compiled a dataset of 6116 georeferenced herbarium specimens, of which 2787 belong to Rubiaceae and Orchidaceae. We used rarefaction methods to explore sampling and diversity patterns, and investigated the altitudinal distribution of rare and/or threatened taxa.Key results – The NMA, which houses about 1500 vascular plant taxa, is the richest documented area for Rubiaceae in Atlantic Central Africa (ACA) and the fifth for Orchidaceae, with respectively 281 and 111 taxa. Among these taxa, 178 (45%) are endemic to ACA and 67 (17%) are considered globally threatened according to IUCN categories and criteria. We show that higher elevation areas (> 750 m), which are also the main areas targeted for mining, are the richest in endangered and/or rare species. Three new records for Cameroon are reported here.Conclusion – The NMA represents an Important Plant Area of Cameroon as confirmed by its exceptional plant diversity (> 20% of the total Flora of Cameroon), by the concentration of many threatened and/or restricted range species (10 taxa are strict endemics of the massif) as well as by the threat on rare habitats (i.e. the submontane vegetation above ~750 m elevation). A management plan involving in situ and ex situ conservation actions is urgently needed to reduce the potential threats of future mining activities.

Background and aims – The intensive botanical prospections carried out in Gabon since the publication of the national checklist in 2006 have resulted in c. 34 300 new specimens (amounting to 30% of all collections made in the country) and an annual increase of 25 species in average. As a result, 5175 species of vascular plants are now recorded from Gabon, of which 650 are considered endemic. However, most of the recent discoveries have not yet been published. This paper is the first of a series documenting additions to the flora of Gabon, and new records of poorly known species. It concerns specifically new records from the Lower Ogooué Ramsar site, the third largest delta of Africa, and certainly the most intact, which includes 80% of the country’s wetlands and a wide variety of other habitats. Methods – The new records presented here come essentially from fieldwork conducted in Gabon between 2008 and 2016 by the authors and colleagues. Further information comes from the study of herbarium specimens in BR, BRLU, K, LBV, MO, P and WAG. For each species, information on distribution and ecology is given, and the studied Gabonese collections listed. In case of rare or range-restricted species, collections from other countries are also listed, and a distribution map is provided, as well as an evaluation of the conservation status based on the categories and criteria of the IUCN Red List. Key results – We report 18 additions to the flora of Gabon, including four genera new to the country (Capparis, Gisekia, Hoffmanniella and Leptochloa) and the first records of the neotropical Justicia secunda being naturalised in tropical Africa. New distribution records are also provided for 16 rare Gabonese endemics or near-endemics. Some species are also newly reported from Cameroon (Cissus leemansii, Salacia coronata) and Equatorial Guinea (Cissus leemansii, C. louisii, Lychnodiscus grandifolius, Placodiscus resendeanus, Rutidea gabonensis, Uvaria bipindensis). Two species, which were reported in the 2006 checklist based on misidentifications, are excluded from the Gabonese flora., SCOPUS: ar.j, info:eu-repo/semantics/published

The fossil record in tropical Africa suggests that dry conditions during the Ice Ages caused expansion of savannahs and contraction of the rainforest. Forest refugia have been proposed to be located in areas of Central Africa that currently harbour high rates of endemic species. However, to what extent the forest was fragmented remains unknown. Nuclear microsatellites and plastid sequences of 732 trees of two species occurring in the same habitat—mature lowland evergreen rainforests—but with remarkably different dispersal capacities—animal versus gravity—were analysed. Geographical information system tools revealed intraspecific lineages partially congruent across the two species, suggesting common past barriers to gene flow in Central Africa. According to approximate Bayesian computation, the intraspecific genetic clusters diverged during the Pleistocene (less than 2 Ma), so that intraspecific differentiation is the appropriate scale to test the aridification effect of the Ice Ages on tree populations. Demographic tests revealed clear genetic signals of population expansion in both taxa, possibly following bottleneck events after forest fragmentation, with stronger evidence of expansion after the Penultimate rather than after the Last Glacial Maximum. The differential dispersal capacity may have modulated the particular response of each species to climate change, as revealed by the stronger evidence of expansion found in the animal-dispersed species than in the gravity-dispersed one.

Background and aims – Diospyros (Ebenaceae), a large genus with a mostly tropical distribution, includes 736 species worldwide, 104 of which occur in continental Africa. During recent field work in west-central Gabon, two new species of Diospyros were collected. They are described and illustrated here, and compared with their most similar relatives. Preliminary conservation status assessments are also provided.Methods – Normal practices of herbarium taxonomy were applied to study all available herbarium material, mainly from BR, BRLU, LBV, MO, P and WAG. The conservation status of both species was evaluated following the IUCN Red List Categories and Criteria.Key results – Diospyros cleistantha O.Lachenaud & G.E.Schatz occurs in the Atlantic regions of Cameroon, Equatorial Guinea and Gabon; it belongs to D. sect. Calvitiella and closely resembles D. zenkeri and D. iturensis. Diospyros subargentea O.Lachenaud, Dauby & G.E.Schatz is endemic to west-central Gabon; it belongs to D. sect. Noltia and most closely resembles D. soyauxii. The conservation status of the two species is assessed as Endangered and Vulnerable, respectively.

International audience; Very high spatial resolution (VHSR) optical satellite imagery has shown good potential to provide non-saturating proxies of tropical forest aboveground biomass (AGB) from the analysis of canopy texture, for instance through the Fourier Transform Textural Ordination method. Empirical case studies however showed that the relationship between Fourier texture features and forest AGB varies across forest types and regions of the world, limiting model transferability. A better understanding of the biophysical mechanisms on which canopy texture – forest AGB relation relies is a prerequisite to move toward broad scale applications. Here we simulated VHSR optical canopy scenes in identical sun-sensor geometry for 279 1-ha tropical forest inventory plots distributed across the tropics. Our aim was to assess the respective merits and complementarity of two types of texture analysis techniques (i.e. Fourier and lacunarity) on a set of forests with contrasted structure and geographical origin, and develop a general texture-based approach for tropical forest AGB mapping. Across forests, Fourier texture captured a gradient of stands mean crown size reflecting well the progressive changes in stand structure throughout forest aggradation phase (e.g. Pearson's r=−0.42 with basal area) while lacunarity texture captured a gradient of canopy openness (, i.e. Pearson's r=−0.57 with stand gap fraction). Both types of texture indices were highly complementary for predicting forest AGB at the global level (so-called FL-model). The residual error of the FL-model was structured across sites and could be partially captured with a bioclimatic proxy, further improving the performance of the global model (so-called FLE-model) and reducing site-level biases. The FLE model was tested on a set of real Pleiades images covering a mosaic of high-biomass forests in the Congo basin (mean AGB over 49 field plots: 359±98Mgha−1), leading to a significant relationship (R2=0.47 on validation data) with reasonable error levels (

AimIn this study we identified large-scale variation in tree species composition across tropical African forests and determined the underlying environmental and historical factors.LocationTropical forests from Senegal to Mozambique.MethodsDistribution data were gathered for 1175 tree species in 455 sample sites scattered across tropical Africa, including all types of tropical forests (wet, moist, dry, and lowland to moderate elevation montane forests). The value of elevation and 19 climatic variables extracted from the BIOCLIM data set were assigned to each sample site. We determined the variation in species composition using correspondence analysis and identified the environmental correlates. We defined floristic clusters according to species composition and identified the characteristic species using indicator analysis.ResultsWe identified a major floristic discontinuity located at the Albertine rift that separated the dry, moist and wet forests of West and Central Africa (the entire Guineo-Congolian Region) from the upland and coastal forests of East Africa. Except for the Albertine Rift, we found no evidence to support the other proposed floristic discontinuities (Dahomey Gap etc.). We detected two main environmental gradients across tropical African forests. The rainfall gradient was strongly correlated with the variation in tree species composition in West and Central Africa. The elevation/temperature gradient highlighted the major floristic differences within East Africa and between East Africa and the Guineo-Congolian Region, the latter being most probably due to the geological disruption and associated climatic history of the East African uplift.Main conclusionsWe found floristic evidence for three main biogeographical regions across the tropical African forests, and described six floristic clusters with particular environmental conditions within these regions: Coastal and Upland for East Africa, Dry and Wet-Moist for West Africa, and Moist and Wet for Central Africa.

Aim: Our aim was to document African rain forest tree diversity patterns to test whether they support one of the following hypotheses: the structure of tree species diversity is at equilibrium and mostly driven by neutral processes (H0); the structure of tree species diversity results from Pleistocene forest cover dynamics (H1); or the structure of tree species diversity results from ecological sorting along environmental gradients (H2). Location: West Central Africa: the hilly region of Gabon, a putative Pleistocene forest refuge, and the adjacent flat littoral region, putatively colonized by forests from the hilly region after the last glaciation. Methods: We used 103 standardized 0.1-ha tree plots distributed among five landscapes in the two regions. We partitioned the tree diversity within and among plots at a local and regional scale using the Hurlbert effective number of species framework. The explanatory power of geographical and elevational distances on species turnover was tested. At the landscape scale, we partitioned the beta diversity into nestedness and turnover components. Results: Mean alpha and gamma diversities were much higher in the hilly region, where differences in elevation explained a significant part of species turnover. Substantial species turnover correlated with geographical distance also occurred in the littoral region despite its low elevational heterogeneity. Floristic turnover between plots from different regions remained stable whatever the elevational/geographical distances. At the regional scale, species replacement remained the main contributor to beta diversity (low nestedness values). Main conclusions: The heterogeneous distribution of alpha and gamma diversity, similar levels of species turnover among plots and the low contribution of the nestedness component to beta diversity between hilly and littoral landscapes do not support hypotheses H0 and H1. The combined impacts of limited dispersal and ecological sorting along environmental gradients (H2) can explain patterns within regions. The marked floristic discontinuity between regions could reflect contrasting histories (two distinct refugia) although the role of contrasting environments cannot be discounted.

Aim Large trees (d.b.h. 70 cm) store large amounts of biomass. Several studies suggest that large trees may be vulnerable to changing climate, poten- tially leading to declining forest biomass storage. Here we determine the importance of large trees for tropical forest biomass storage and explore which intrinsic (species trait) and extrinsic (environment) variables are associated with the density of large trees and forest biomass at continental and pan-tropical scales. Location Pan-tropical.

International audience; The biogeographic history of the African rain forests has been contentious. Phylogeography, the study of the geographic distribution of genetic lineages within species, can highlight the signatures of historical events affecting the demography and distribution of species (i.e. population fragmentation or size changes, range expansion/contraction) and, thereby, the ecosystems they belong to. The accumulation of recent data for African rain forests now enables a first biogeographic synthesis for the region. In this review, we explain which phylogeographic patterns are expected under different scenarios of past demographic change, and we give an overview of the patterns detected in African rain forest trees to discuss whether they support alternative hypotheses regarding the history of the African rain forest cover. The major genetic discontinuities in the region support the role of refugia during climatic oscillations, though not necessarily following the classically proposed scenarios. We identify in particular a genetic split between the North and the South of the Lower Guinean region. Finally we provide some perspectives for future study.; L’histoire biogéographique des forêts tropicales africaines reste controversée. La phylogéographie, l’étude de la répartition géographique des lignées génétiques au sein des espèces, peut révéler la signature d’événements historiques qui ont affecté la démographie et la répartition des espèces (fragmentation ou changement de taille de population, extension/contraction de leur distribution) et de leurs écosystèmes constitutifs. La récente accumulation de données pour les forêts pluviales africaines permet une première synthèse biogéographique. Dans cette revue, nous expliquons quels patrons phylogéographiques sont attendus selon différents scénarios de changement démographique passé, puis nous donnons un aperçu des patrons détectés chez les arbres des forêts pluviales africaines, afin de discuter s’ils appuient des hypothèses alternatives concernant l’histoire de la couverture forestière. Les discontinuités génétiques majeures dans la région tendent à soutenir le rôle des refuges lors des oscillations climatiques, mais pas forcément selon les scénarios classiquement proposés. Elles mettent notamment en évidence une discontinuité génétique entre le Nord et le Sud de la basse Guinée. Nous terminons par quelques perspectives pour des études futures.

Accurately monitoring tropical forest carbon stocks is an outstanding challenge. Allometric models that consider tree diameter, height and wood density as predictors are currently used in most tropical forest carbon studies. In particular, a pantropical biomass model has been widely used for approximately a decade, and its most recent version will certainly constitute a reference in the coming years. However, this reference model shows a systematic bias for the largest trees. Because large trees are key drivers of forest carbon stocks and dynamics, understanding the origin and the consequences of this bias is of utmost concern. In this study, we compiled a unique tree mass dataset on 673 trees measured in five tropical countries (101 trees > 100 cm in diameter) and an original dataset of 130 forest plots (1 ha) from central Africa to quantify the error of biomass allometric models at the individual and plot levels when explicitly accounting or not accounting for crown mass variations. We first showed that the proportion of crown to total tree aboveground biomass is highly variable among trees, ranging from 3 to 88 %. This proportion was constant on average for trees < 10 Mg (mean of 34 %) but, above this threshold, increased sharply with tree mass and exceeded 50 % on average for trees ≥ 45 Mg. This increase coincided with a progressive deviation between the pantropical biomass model estimations and actual tree mass. Accounting for a crown mass proxy in a newly developed model consistently removed the bias observed for large trees (> 1 Mg) and reduced the range of plot-level error from −23–16 to 0–10 %. The disproportionally higher allocation of large trees to crown mass may thus explain the bias observed recently in the reference pantropical model. This bias leads to far-from-negligible, but often overlooked, systematic errors at the plot level and may be easily corrected by accounting for a crown mass proxy for the largest trees in a stand, thus suggesting that the accuracy of forest carbon estimates can be significantly improved at a minimal cost.

A theoretical framework based on Hill numbers has recently been advocated to measure and partition diversity sensu stricto. Hill numbers can be interpreted intuitively as eff ective number of species (ENS). Th ey conform to the so-called replication principle allowing a mathematically coherent multiplicative partitioning of diversity. Th ey form a family of ENS defi ned by the parameter q which controls the weight attributed to rare species. Despite its advantages, this framework was developed without considering its robustness when treating community samples. In this study, we fi rst show that Hurlbert diversity indices (expected number of species among k individuals) can be transformed into ENS that conform asymptotically to the replication principle while controlling the weight given to rare species through parameter k . We investigate the statistical properties of Hill and Hurlbert ENS using simulated communities with contrasted diversity. Th e properties of multiplicative beta diversity estimators based on ENS are also characterized by simulating communities with diff erent levels of diff erentiation. We show that Hurlbert ENS provides a better statistical performance than Hill numbers when dealing with small sample sizes. By contrast, Hill numbers and their estimators suff er from substantial bias except when rare species have a low weight ( q 2). An estimator of ENS estimating both Hill numbers for q 2 and Hurlbert ENS for k 2 is shown to give the best performance and is recommended for processing real datasets when rare species receive low weight. In order to better take account of rare species, current estimators of Hill numbers are not recommended when sample size is too low while Hurlbert’s ENS performs reliably. In conclusion, while Hill numbers possess some interesting mathematical properties that are not shared by Hurlbert’s ENS, the latter outperforms Hill numbers in terms of statistical properties and is well suited to processing community samples, as illustrated on a real dataset.

Since the publication of the Gabon Checklist in 2006, intensive fieldwork activity has led to the discovery of many novelties. We document here 61 new records for the flora of Gabon, including nine new generic records. Five taxa are also removed from the Gabon flora. © 2011 Trustees of the Royal Botanic Garden Edinburgh.

Our aim was to evaluate the extent to which we can predict and map tree alpha diversity across broad spatial scales either by using climate and remote sensing data or by exploiting spatial autocorrelation patterns in tropical rain forest, West Africa and Atlantic Central Africa.

International audience; Geographic patterns of genetic variation at chloroplast markers have been successfully used to address the phylogeography and the demographic history of many plant species. Very few studies have however been conducted in important tropical centers of plant biodiversity like the African rainforests. The phylogeography of a tree species widespread in Central African mature forests, Greenwayodendron suaveolens subsp. suaveolens (Annonaceae), was investigated in the Lower Guinea phytogeographic domain (essentially Gabon and Cameroon) by sequencing an intergenic spacer of the chloroplast genome (trnC-petN1R). A total of 11 polymorphic sites, including nine single nucleotide polymorphisms (SNPs), two insertions/deletions and two inversions, defined 12 haplotypes. The taxon is represented by two sympatric varieties (var. suaveolens and var. gabonica) that carried distinct and relatively divergent haplotypes. These varieties, also well distinguishable morphologically, might therefore represent true biological species. The variety suaveolens, more common and more widespread than the variety gabonica, was represented by ten haplotypes. This taxon showed a weak but statistically significant phylogeographic structure, indicating that two sets of related haplotypes essentially occurred respectively in the northern and the southern hemispheres. These results suggest that the distribution of Greenwayodendron suaveolens subsp. suaveolens, which is currently continuous in the Lower Guinea domain, might have been more fragmented in the past, possibly in relation with Pleistocene forest fragmentation.

Large tropical trees and a few dominant species were recently identified as the main structuring elements of tropical forests. However, such result did not translate yet into quantitative approaches which are essential to understand, predict and monitor forest functions and composition over large, often poorly accessible territories. Here we show that the above-ground biomass (AGB) of the whole forest can be predicted from a few large trees and that the relationship is proved strikingly stable in 175 1-ha plots investigated across 8 sites spanning Central Africa. We designed a generic model predicting AGB with an error of 14% when based on only 5% of the stems, which points to universality in forest structural properties. For the first time in Africa, we identified some dominant species that disproportionally contribute to forest AGB with 1.5% of recorded species accounting for over 50% of the stock of AGB. Consequently, focusing on large trees and dominant species provides precise information on the whole forest stand. This offers new perspectives for understanding the functioning of tropical forests and opens new doors for the development of innovative monitoring strategies., SCOPUS: ar.j, info:eu-repo/semantics/published

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher's alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼40,000 and ∼53,000, i.e. at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼19,000-25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼4,500-6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa., 0, SCOPUS: ar.j, info:eu-repo/semantics/published

Scorodophloeus zenkeri is a tropical tree from mature rainforests of Central Africa, locally threatened by overexploitation. Ten nuclear microsatellite markers, amplifiable in two multiplexed reactions, were developed and characterized in one population. The levels of polymorphism observed (3–15 alleles per locus, expected heterozygosity ranging from 0.198 to 0.905) point at the promising application of the markers for conservation purposes regarding the location of past forest refugia, assessment of mating system and evaluation of genetic diversity in isolated and threatened populations.

Taxonomic classification based on morphology alone can prove difficult. This is the case of the polymorphic forest tree species Santiria trimera in Africa, whose classification has remained controversial for over a century. Studies combining chloroplast and nuclear DNA sequences show the existence of several phylogenetic clades in this taxon, with some occurring in sympatry in western Central Africa suggesting the existence of at least two species. By combining genetic and morphological markers, we aim to assess the species delimitation in the Santiria species complex. Morphological trait (trunk, leaflet, flower and fruit characteristics) analysis using 223 standing individuals and 103 herbarium samples were combined with genetic analyses using 479 individuals genotyped at eight microsatellite markers. Genetic clusters were identified using Bayesian assignment in order to delimit species following the Biological Species Concept and to identify distinctive characters from morphometric analyses in retrospect. Three genetic clusters were identified and found to occur in sympatry. The type of inflorescence and the colour of unripe fruit were the most discriminant morphological traits among those genetic clusters, while many quantitative traits showed overlapping distributions between genetic clusters and explain the difficulty encountered by previous botanists to resolve the taxonomy of Santiria. The combination of genetic and morphological data suggests the presence of three species within the taxon Santiria trimera from western Central Africa. This work should guide a taxonomic revision within the genus Santiria in Africa., SCOPUS: ar.j, info:eu-repo/semantics/published

Comparative phylogeography is an effective approach to assess the evolutionary history of biological communities. We used comparative phylogeography in fourteen tree taxa from Lower Guinea (Atlantic Equatorial Africa) to test for congruence with two simple evolutionary scenarios based on physio-climatic features 1) the W-E environmental gradient and 2) the N-S seasonal inversion, which determine climatic and seasonality differences in the region. We sequenced the trnC-ycf6 plastid DNA region using a dual sampling strategy: fourteen taxa with small sample sizes (dataset 1, mean n = 16/taxon), to assess whether a strong general pattern of allele endemism and genetic differentiation emerged; and four taxonomically well-studied species with larger sample sizes (dataset 2, mean n = 109/species) to detect the presence of particular shared phylogeographic patterns. When grouping the samples into two alternative sets of two populations, W and E, vs. N and S, neither dataset exhibited a strong pattern of allelic endemism, suggesting that none of the considered regions consistently harboured older populations. Differentiation in dataset 1 was similarly strong between W and E as between N and S, with 3-5 significant F ST tests out of 14 tests in each scenario. Coalescent simulations indicated that, given the power of the data, this result probably reflects idiosyncratic histories of the taxa, or a weak common differentiation pattern (possibly with population substructure) undetectable across taxa in dataset 1. Dataset 2 identified a common genetic break separating the northern and southern populations of Greenwayodendron suaveolens subsp. suaveolens var. suaveolens, Milicia excelsa, Symphonia globulifera and Trichoscypha acuminata in Lower Guinea, in agreement with differentiation across the N-S seasonal inversion. Our work suggests that currently recognized tree taxa or suspected species complexes can contain strongly differentiated genetic lineages, which could lead to misinterpretation of phylogeographic patterns. Therefore the evolutionary processes of such taxa require further study in African tropical rainforests., Journal Article, SCOPUS: ar.j, info:eu-repo/semantics/published

Garcinia has some 260 species and is often regarded as a genus with a difficult taxonomy. No recent treatment is available for the botanically rich Lower Guinea phytogeographical region. This study aims at partly filling this gap. First, several taxonomic problems are solved. G. chromocarpa is reduced to a variety of G. quadrifaria. G. gnetoides and G. granulata are both synonyms of G. quadrifaria. G. zenkeri is a synonym of G. densivenia and lectotypes are being designated for both names. G. brevipedicellata is a synonym of G. afzelii, as is G. antidysenterica for which a lectotype is designated. Second, two new species endemic to Gabon are described: Garcinia gabonensis Sosef & Dauby and Garcinia obliqua Sosef & Dauby. Finally, an identification key to all species present in the Lower Guinea region is provided. A few remaining West African species names could not be placed with certainty, because the type material was lost or not traced yet. One is a Rutaceae while the remaining three are provisionally to be regarded as synonyms of G. smeathmannii.

PREMISE OF THE STUDY Microsatellite loci were developed in the endangered Pericopsis elata using a combination of low-cost procedures. METHODS AND RESULTS Microsatellite isolation was performed simultaneously on three distinct species through a newly available procedure that associates multiplex microsatellite enrichment and next-generation sequencing, allowing the rapid and low-cost development of microsatellite-enriched libraries through the use of a 1/32nd GS-FLX plate. Genotyping using M13-like labeling in multiplexed reactions allowed additional cost savings. From 72 primers selected for initial screening, 21 positively amplified P. elata, and 11 showed polymorphism with two to 11 alleles per locus and a mean value of 5.4 alleles per locus. CONCLUSIONS These microsatellite loci will be useful to further investigate the level of genetic variation within and between natural populations of P. elata in Africa.

A new species Afrothismia gabonensis Dauby & Stevart (Burmanniaceae) is described from the Pongara National Park (Gabon). It is the second Afrothismia species recorded from this country and the twelfth of the genus. The new species mainly differs from Afrothismia winkleri by its dorsal tepals which are much longer. Information on the species’ ecology, phenology and distribution is provided.