Burkholderia endophytes were identified within the leaves of non-nodulated members of the genus Psychotria. In contrast to leaf-nodulated Psychotria species, which are known to accommodate their endosymbionts into specialized endosymbiont-housing structures, non-nodulated species lack bacterial leaf nodules and harbor endosymbionts intercellularly between mesophyll cells. Based on molecular data (rps16, trnG, and trnLF), the phylogenetic reconstruction of the host plants revealed a separate origin of leaf-nodulated and non-nodulated Psychotria species. Despite a distinct phylogenetic position of the two host clades, the endophytes of the non-nodulated plants were not placed into a single monophyletic group but were found to be closely related to the leaf-nodulated endosymbionts. The observation of genetically similar endophytes in both nodulated and non-nodulated Psychotria lineages suggests that the host plant is playing a crucial role in the induction of leaf nodule formation. Moreover, the concentration of endosymbionts into specialized leaf nodules may be considered as a more derived evolutionary adaptation of the host plant, serving as an interface structure to facilitate metabolic exchange between plant and endosymbiont.

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The littoral forests of the Libreville area (Gabon) and their importance for conservation: description of a new endemic Psychotria species (Rubiaceae)Background -A new species of Rubiaceae, Psychotria wieringae O.Lachenaud, is described and illustrated. Methods -Normal practises of herbarium taxonomy have been applied. Key results -P. wieringae is endemic to the Libreville peninsula (Gabon), where it is locally abundant in the undergrowth of littoral forests on sandy soils. It is related to P. gabonica Hiern but differs in its pale bark, glabrous inflorescences, flower colour, and leaves with a prominent midrib on the upper surface. IUCN assessment -The species is considered as Endangered EN B2ab(i,ii,iii,iv,v) according to IUCN criteria. Its survival in situ will likely depend on the maintenance of the subpopulation at the "Ferme des crocodiles", situated in the Raponda-Walker Arboretum. The occurence of several other endemic species in the area, and their conservation, are also discussed.Contexte -Une nouvelle espèce de Rubiaceae, Psychotria wieringae O.Lachenaud, est décrite et illustrée. Méthodes -Les méthodes usuelles de taxonomie d'herbier ont été appliquées. Résultats-clés -P. wieringae est endémique de la péninsule de Libreville (Gabon) où il est localement abondant dans le sous-bois des forêts littorales sur sol sableux. Voisin de P. gabonica Hiern, il en diffère notamment par son écorce claire, les inflorescences glabres et la couleur des fleurs, et par la nervure médiane des feuilles saillante à la face supérieure. Estimation UICN -L'espèce est considérée comme En danger EN B2ab(i,ii,iii,iv,v) selon les critères de l'UICN. Sa survie en condition in situ dépendra probablement du maintien de la sous-population de la "Ferme des crocodiles", située dans l'Arboretum Raponda-Walker. La présence de plusieurs autres espèces endémiques dans la région, et leur conservation, sont également discutées.

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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, including Balthasaria mannii (Oliv.) Verdc., 1969 (Pentaphylacaceae) and Psychotria exellii R. 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.

Urban development is an increasing threat to the integrity of formerly remote protected areas, in some cases resulting in their downgrading, downsizing or degazetting. One-quarter of previously remote protected areas are now within 17 km of a city and thus face the threat of urbanization. Here we describe a case of avoided downgrading, downsizing and degazetting of a protected area in the Mondah forest of Gabon, north of Libreville. Since its creation in 1934 the Forêt Classée de la Mondah has been downsized regularly, losing 40% of its area over 80 years. During this time the forest surrounding the Forêt Classée was subject to usage for urban and peri-urban needs, including agriculture, sand extraction, collection of medicinal plants, ceremonies, and housing construction. In 2010 the area was threatened with further downsizing. The presence of narrowly endemic plant species in the area was suspected, and mapping and evaluation of these species was proposed in an effort to maintain the protected area boundaries. Botanical field work, including ex situ conservation measures and participant observation in nearby forest communities, was conducted; 24 endemic species, all threatened by urbanization, were evaluated using the criteria for the IUCN Red List of Threatened Species. The borders of the protected area were maintained because of its role in maintaining irreplaceable habitat for threatened species. The area was renamed Raponda Walker Arboretum in 2012

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.

Three new species of Rubiaceae from Central Africa are described and illustrated. Chassalia lutescens O.Lachenaud & D.J.Harris (widespread from Cameroon to Democratic Republic of Congo) is recognised inter alia by the T-shaped ventral furrow of the seeds and the orange-yellow discoloration of inflorescences in herbarium specimens. Psychotria nodiflora O.Lachenaud & D.J.Harris (Central African Republic, Congo-Brazzaville and Democratic Republic of Congo), belonging to Psychotria subgen. Psychotria sect. Involucratae, is unique among African species of the genus in having paired axillary inflorescences. Psychotria pteropus O.Lachenaud & D.J.Harris (Central African Republic and Democratic Republic of Congo) belongs to Psychotria subgen. Tetramerae; it is closely related to P. leptophylla Hiern but differs in its narrow corolla tube and globose to ellipsoid fruits.