Résumé
Background and aims - The intensive botanical prospections carried out in Gabon since the publication of the national checklist in 2006 have resulted in c. 34300 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 Ogooue 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 heibarium 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.