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Malgré l’idée couramment admise d’un territoire couvert d’une forêt homogène, en réalité la Guyane est très hétérogène tant dans la répartition des espèces que des paysages végétaux. Nous évoquerons les différentes voies d’exploration possibles de la biodiversité végétale utilisées jusqu’à présent et leurs perspectives de développement dans le cadre de la mise en place d’un conservatoire botanique en Guyane. Deux exemples seront développés: l’état des connaissances et les stratégies d’acquisition pour les espèces arborescentes forestières mettant l’accent sur l’aspect fragmenté de l’espace forestier ; et l’étude des espèces dites « utiles », associées aux activités humaines, en particulier les plantes liées à l’agriculture traditionnelle, les plantes médicinales et les plantes introduites, dont la présence est liée à l’habitat humain, ancien ou récent. La mise en place du conservatoire botanique à l’échelle de la Région Guyane, portée par la collectivité locale, et soutenue par le ministère de l’Environnement nous permet d’envisager la mise en place d’une structure intégrant les connaissances scientifiques et les connaissances traditionnelles. Médiateur entre l’État, les collectivités, les organismes de recherche, les associations et les communautés, il pourrait devenir un véritable outil de gouvernance de la biodiversité pour la Guyane, mais aussi une plateforme de collaboration internationale à l’échelle du plateau des Guyanes. Despite the widely accepted idea of an area covered with a homogeneous forest, french Guiana is actually very heterogeneous in both distribution of species and forest landscapes. We will discuss the various usual ways for exploration of plant biodiversity and their development through the introduction of a botanical conservatory in french Guiana. Two examples will be developed : the state of knowledge and acquisition strategies for forest tree species with emphasis on the fragmented appearance of the forest area ; and the study of species listed as "useful", associated with human activities, in particular plants related to traditional agriculture, medicinal plants and exotics, whose presence is related to human habitat, old or new. The establishment of the botanical conservatory in the Guiana Region, supported by the « Region Guyane » and by the Ministry of the environment, allows us to set up a structure integrating scientific knowledge and traditional knowledge. This mediator between the state, local collectivities, research organizations, associations and communities, could become a real tool for biodiversity governance for Guiana, and also a platform for international collaboration on the scale of the Guiana Shield.

International audience; The genetic diversity of 221 Mimosa pudica bacterial symbionts trapped from eight soils from diverse environments in French Guiana was assessed by 16S rRNA PCR-RFLP, REP-PCR fingerprints, as well as by phylogenies of their 16S rRNA and recA housekeeping genes, and by their nifH, nodA and nodC symbiotic genes. Interestingly, we found a large diversity of beta-rhizobia, with Burkholderia phymatum and Burkholderia tuberum being the most frequent and diverse symbiotic species. Other species were also found, such as Burkholderia mimosarum, an unnamed Burkholderia species and, for the first time in South America, Cupriavidus taiwanensis. The sampling site had a strong influence on the diversity of the symbionts sampled, and the specific distributions of symbiotic populations between the soils were related to soil composition in some cases. Some alpha-rhizobial strains taxonomically close to Rhizobium endophyticum were also trapped in one soil, and these carried two copies of the nodA gene, a feature not previously reported. Phylogenies of nodA, nodC and nifH genes showed a monophyly of symbiotic genes for beta-rhizobia isolated from Mimosa spp., indicative of a long history of interaction between beta-rhizobia and Mimosa species. Based on their symbiotic gene phylogenies and legume hosts, B. tuberum was shown to contain two large biovars: one specific to the mimosoid genus Mimosa and one to South African papilionoid legumes.

International audience; While the populations of large herbivores are being depleted in many tropical rainforests, the importance of their trophic role in the ecological functioning and biodiversity of these ecosystems is still not well evaluated. This is due to the outstanding plant diversity that they feed upon and the inherent difficulties involved in observing their elusive behaviour. Classically, the diet of elusive tropical herbivores is studied through the observation of browsing signs and macroscopic analysis of faeces or stomach contents. In this study, we illustrate that the original coupling of classic methods with genetic and ethnobotanical approaches yields information both about the diet diversity, the foraging modalities and the potential impact on vegetation of the largest terrestrial mammal of Amazonia, the lowland tapir. The study was conducted in the Guianan shield, where the ecology of tapirs has been less investigated. We identified 92 new species, 51 new genera and 13 new families of plants eaten by tapirs. We discuss the relative contribution of our different approaches, notably the contribution of genetic barcoding, used for the first time to investigate the diet of a large tropical mammal, and how local traditional ecological knowledge is accredited and valuable for research on the ecology of elusive animals.