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Curbing biodiversity loss and its impact on ecosystem services, resilience and Nature’s Contributions to People is one of the main challenges of our generation (IPBES, 2019b, 2019a; Secretariat of the United Nations Convention on Biological Diversity, 2020). A global baseline assessment of the threat status of all of biodiversity is crucial to monitor the progress of conservation policies worldwide (Mace & al., 2000; Secretariat of the United Nations Convention on Biological Diversity, 2021) and target priority areas for conservation (Walker & al., 2021). However, the magnitude of the task seems insurmountable, as even listing the organisms already known to science is a challenge (Nic Lughadha & al., 2016; Borsch & al., 2020; Govaerts & al., 2021). A new approach is needed to overcome this stumbling block and scale-up the assessment of extinction risk. Here we show that analyses of natural history mega-datasets using artificial intelligence allows us to predict a baseline conservation status for all vascular plants and identify target areas for conservation corresponding to hotspots optimally capturing different aspects of biodiversity. We illustrate the strong potential of AI-based methods to reliably predict extinction risk on a global scale. Our approach not only retrieved recognized biodiversity hotspots but identified new areas that may guide future global conservation action (Myers & al., 2000; Brooks & al., 2006). To further work in this area and guide the targets of the post-2020 biodiversity framework (Díaz & al., 2020a; Secretariat of the United Nations Convention on Biological Diversity, 2020; Mair & al., 2021), it will be necessary to accelerate the acquisition of fundamental data and allow inclusion of social and economic factors (Possingham & Wilson, 2005).

International audience; The nearly cosmopolitan tribe Desmodieae (Fabaceae) includes many important genera for medicine and forage. However, the phylogenetic relationships among the infratribal groups circumscribed using morphological traits are still poorly known. In this study, we used chloroplast (rbcL, psbA-trnH) and nuclear (ITS-1) DNA sequences to investigate the molecular phylogeny and historical biogeography of Desmodieae, and infer ancestral states for several vegetative and reproductive traits. Three groups, corresponding to the Desmodium, Lespedeza, and Phyllodium groups sensu Ohashi were retrieved in the phylogenetic analyses. Conflicts in the topologies inferred from the chloroplast and nuclear datasets were detected. For instance, the Lespedeza clade was sister to the groups Phyllodium + Desmodium based on chloroplast DNA, but nested within the Desmodium group based on ITS-1. Moreover, the New Caledonian endemic genera Arthroclianthus and Nephrodesmus were not monophyletic but together formed a clade, which also included Hanslia and Ohwia based on chloroplast DNA. The hypothetical common ancestor of Desmodieae was dated to the Middle Oligocene (ca. 28.3 Ma) and was likely an Asian shrub or tree producing indehiscent loments. Several colonization events towards Oceania, America, and Africa occurred (all less than ca. 17.5 Ma), most probably through long distance dispersal. The fruits of Desmodieae repeatedly evolved from indehiscence to dehiscence. We also showed that indehiscent loments allow for more variability in the number of seeds per fruit than indehiscent legumes. Modularity seems here to allow variability in the number of ovules produced in a single ovary.

International audience; The census of vascular plants across a 10-year interval (1995-2005) at the fringe of a neotropical rainforest (Nouragues inselberg, French Guiana, South America) revealed that species richness decreased, both at quadrat scale (2 m2) and at the scale of the inselberg (three transects, embracing the whole variation in community composition). Juvenile stages of all tree and shrub species were most severely affected, without any discrimination between life and growth forms, fruit and dispersion types, or seed sizes. Species turnover in time resulted in a net loss of biodiversity, which was inversely related to species occurrence. The most probable cause of the observed species disappearance is global warming, which severely affected northern South America during the last 50 years (+2° C), with a concomitant increase in the occurrence of aridity.

Granite inselbergs protrude from forest and savanna in the tropics. They are exposed to harsh climates (alternation of heavy rain and severe drought) and provide little nutrient for plants. Soil animals and humus components were investigated in cyanobacterial crusts close to patches of epilithic vegetation on the surface of the Nouragues inselberg (French Guiana). Three biological crust samples, corresponding to bromeliacean carpets of increasing size (supposed of increasing age), were sampled for faunal and micromorphological studies. Arthropods (mainly mites and insects) were abundant and highly diversified, the more so after enchytraeid worms ate and transformed the cyanobacterial mass. Below the superficial cyanobacterial crust, humus was made of a loose assemblage of enchytraeid faeces where these animals were present, or of a compact assemblage of cyanobacteria and amorphous organic matter where mites were the dominant animal group. Roots abounded in the humified part of the crust. We conclude that soil invertebrates, in particular enchytraeid worms, are important for the accumulation of organic matter on granite outcrops, and so therefore for the encroachment of plant succession.

South American inselbergs constitute singular and fragmented habitats in the tropical rain forest. Pitcairnia geyskesii is restricted to these habitats and exhibits both sexual and asexual reproduction. The genetic structure of populations on three inselbergs in French Guiana is examined by analysis of ten isozyme loci. All analyzed populations show high levels of genetic variation. On average, 63.3% of loci per population were polymorphic, with a mean number of 2.21 alleles per polymorphic locus, and mean observed and expected heterozygosities of 0.185 and 0.183, respectively. The analyses of genetic variability displayed at different levels (inselbergs, subpopulations, and mats) give different but complementary information. A significant multilocus disequilibrium was detected in one subpopulation, whereas none was observed within the whole populations sampled on the three inselbergs. Tests on spatial genetic structure indicate a patchy distribution of genotypes on two inselbergs. The data give some insights on the reproductive behavior of P. geyskesii. (1) Efficient sexual reproduction leads to seed recruitment at the level of the inselberg. (2) Both clonality and seed recruitment occur within mats. (3) Vegetative spread by fragmentation is involved in the establishment of new mats. There is substantial differentiation (F(ST) = 0.322) and low gene flow among inselbergs (Nm = 0.234). High genetic diversity within inselbergs appears as a consequence of the association of genet longevity induced by clonal replication and recruitment of new genets produced by sexual reproduction.

Tropical forests can be described as a mosaic of juxtaposed eco-units corresponding to different stages of regeneration after treefals. However, these small-scale regeneration mechanisms alone cannot account for the different patterns of species distribution, plant communities and population structures found in this habitat. The presence of charcoal layers in the soil and the study of sediments along streams suggest that large-scale forest fires deeply affected the tropical forest vegetation, even in high rainfall areas such as French Guiana. Many atypical plant distribution and population structure patterns, in relation to what would be expected from present-time regeneration processes, can be explained by these large-scale events which happened during the last few thousand years.

Tropical inselbergs are isolated elevations with a special type of vegetation and surrounded by rain forest. The paper describes, using the field methods of Braun-Blanquet, combined with numerical analysis (clustering, Correspondence Analysis), plant communities on French Guianan inselbergs. Six new associations are described: Portulacetum sedifolii, Furcraeetum foetidae, Ananasetum annassoidis, Stylosanthetum guianensis, Axonopetum ramosi and (endemic to the Guianan inselbergs) Pepinietum geyskesii – with three subassociations. The six vegetation units reflect different combinations of environmental factors such as local relief, insolation, water availability and soil depth. All syntaxa show a low species diversity. Species of Cyperaceae, Poaceae, Lentibulariaceae and Bromeliaceae are predominant, whereas families typical of other South American inselbergs (Velloziaceae and Cactaceae), are missing or scarce. Similarities between vegetation units of South American and African inselbergs are emphasized.

Pitcairnia geyskesii is a saxicolous bromeliad endemic to the granitic inselbergs of French Guiana and Surinam. Seven polymorphic microsatellite markers were characterized to investigate the polymorphism among individuals sampled on five inselbergs in French Guiana. The total number of alleles per locus varied from four to 14. Mean observed heterozygosities at each microsatellite locus ranged from 0.114 to 0.629. This set of microsatellites offers an efficient tool for more detailed investigations on the genetic structure of fragmented populations living on such a singular and insular habitat within tropical rainforest.

During the annual carbohydrate cycle, starch and soluble sugar concentrations were quite similar in the lower and upper parts of the trunk of sweet cherry. The seasonal variations were characterized by a maximum carbohydrate content between summer and mid-November and at the end of winter. Bloom and fruit development were distinguished by carbohydrate depletion. The effects of the removal of low branches on the level of the carbohydrates were related to the time of pruning. After summer pruning, the middle and upper parts of the trunk contained the highest concentrations of starch and soluble sugars. The following year, starch had completely disappeared in the upper and lower parts of the trunk. The autumn pruning induced an increase in starch and soluble sugar levels in the upper part. The winter pruning mainly induced a rapid accumulation of soluble sugars in the upper part only.

Summary In 1-year-old Ailanthus seedlings, drought stress first induces hydrolisis of carbohydrates stored which are mainly accumulated in the taproot. After the outset of wilting (8–10 days after watering cessation), this phenomena is connected with an increase of soluble sugars in the root system and stem. During this period, proteins are less affected even increase significantly in the stem after leaf-fall. When the abscission of the terminal bud occurs (at the end of the experience), one note an important decrease in carbohydrate, lipid and protein contents of the tap—root and stem. On the contrary, the lateral roots are characterized by high soluble sugar level, starch synthesis, stability of proteins and lipid accumulation. In the nonstressed seedlings, the composition of the soluble sugar fraction of the different perennial parts is marked by the dominance of sucrose. During the stress treatment, fructose becomes the most important sugar in the stem and tap-root. In the lateral roots, the fructose ...

International audience; Inselbergs are hills rising abruptly from the surrounding plains where cyanobacteria are the only living organisms under conditions of intense solar radiation. A survival mechanism to prevent UV-damage has been associated with synthesis of the ultraviolet-screening, photostable sheath pigment scytonemin. The organic extract of Scytonema sp., collected on the Mitaraka inselberg, French Guyana, yielded three new pigments, tetramethoxyscytonemin (1), dimethoxyscytonemin (2), and scytonine (3), derived from the scytoneman skeleton of scytonemin. These structures were assigned mainly on the basis of (1)H and (13)C NMR and MS experiments.

The analysis of most plant populations in natural forests clearly retraces the mechanisms of sylvigenesis, based on the occurrence of small-scale incidents — in particular treefall gaps — more or less regularly distributed in time and space (van der Meer et al. chapter 24). However, a number of ‘anomalies’ detected in the population structure or in the distribution of some species cannot be adequately explained by the internal dynamic processes which occur on the century time scale. Plants react at different speeds to perturbations, and major events, even very ancient ones such as the perturbations recorded in the sediments, have probably also left a durable mark in the present organisation of the vegetation. We can therefore hypothesise that relatively ancient events, which would have occurred on a much larger scale than treefall gaps, would have caused large modifications of the forest ecosystems and left long-lasting tell-tale signs.

The term ‘inselberg’, proposed by Bonhardt (1900), characterises isolated rock outcrops consisting mainly of Precambrian granites or gneisses. The origin, geology and geomorphology of inselbergs have been widely studied (Bremer & Jennings 1978, Twidale & Bourne 1978, Twidale 1980). In South America, classical whale back forms dominate and are scattered throughout the Guiana and Brazilian Shield up to East Bolivia. These hills rise abruptly from the surrounding landscape and constitute singular habitats in tropical rain forest. Due to the poorly developed soils and extreme microclimatic fluctuations, they are colonised by vegetation drastically different from the surroundings. Thus, they reflect a clear habitat fragmentation and constitute functional ‘terrestrial’ islands (Prance 1996).