INTRODUCTION
⌅The Republic of Equatorial Guinea is formed by an oceanic island called Annobón (17 km²), four continental islands: Corisco (15 km2), Elobey Grande (2.27 km²) and Elobey Chico (0.19 km²), and Bioko (2,017 km²), and a continental region, Río Muni. Politically, it is divided into seven provinces: Bioko Norte and Bioko Sur, Annobón, Litoral, Wele-Nzas, Kie-Ntem, and Centro Sur. The last four are on the mainland. Equatorial Guinea has maintained a close relationship with Europe. The island of Bioko was discovered in 1471, becoming part of the Portuguese crown. Four years later the same happened with the island of Annobon. In 1777, with the signing of the Treaty of San Ildefonso between Spain and Portugal, Equatorial Guinea passed to the Spanish crown, and would remain so until 1968, when it achieved its independence.
Río Muni is the continental region of Equatorial Guinea. It is in the Atlantic sector of Central Africa. It occupies 26017 km² between latitudes 1°01’N and 2°21’N, and longitudes 9°00 ‘E (the Atlantic coast) and 11°20’E. It limits to the north with Cameroon, along the Ntem River, and to the east and south with Gabon. Río Muni is part of a large granite plateau that runs from the Atlantic coast to the Adamawa Massif on the north, to the Angola Plateau on the south and to the Congo River Basin on the west. This granite block comes into contact with sandstones and marls of the Tertiary by the west and with sandstones and slates of the Secondary by the southwest.
From a biogeographical point of view, Río Muni is included entirely in the strip of lowland and plain African rainforest, which barely exceeds 1000 m in altitude. It is integrated within the Guineo-Congolian Region, in the Nigerian-Cameroonian Province (Takhtajan 1986: 199Takhtajan A. 1986. Floristic regions of the world. University of California, Berkeley.; Linder & al. 2012Linder H.P., de Klerk H.M., Born J., Burgess N.D., Fjeldså J. & Rahbek C. 2012. The partitioning of Africa: Statistically defined biogeographical regions in sub-Saharan Africa. Journal of Biogeography 39: 1189-1205.; Droissart & al. 2018Droissart V., Dauby G., Hardy O.J., Deblauwe V., Harris D.J., Janssens S., Mackinder B.A., Blach-Overgaard A., Sonké B., Sosef M.S.M., Stévart T., Svenning J.C., Wieringa J.J. & Couvreur T.L.P. 2018. Beyond trees: Biogeographical regionalization of tropical Africa. Journal of Biogeography 45: 1153-1167.). This biogeographical province contains several endemic genera and many endemic species, and is currently covered by dense equatorial rainforests.
The soils of Río Muni are derived from the decomposition of granite and gneiss. They are lateritic soils with a concentration of iron oxide, aluminum, titanium, and magnesium hydrates higher than 30% (De Castro & De la Calle 1985De Castro M.L. & De la Calle M.L. 1985. Geografía de Guinea Ecuatorial. Secretaría General Técnica. Ministerio de Educación y Ciencia, Madrid.; Fa 1991: 19Fa J.E. 1991. Conservación de los Ecosistemas Forestales de Guinea Ecuatorial. IUCN, Gland, Cambridge.).
The climate is equatorial with two dry seasons: one from July to September, the most important, and another from December to mid-February, and two rainy seasons: one from September to November and another from March to June. The average temperature is 25ºC with an oscillation not exceeding 5ºC. The average relative humidity is 90%, dropping slightly, to 85%, in the dry season. Annual precipitation ranges from 1800 to 3800 mm mainly between the months of September to December, with a considerable decrease in precipitation from March to May (De Castro & De la Calle 1985: 15-16De Castro M.L. & De la Calle M.L. 1985. Geografía de Guinea Ecuatorial. Secretaría General Técnica. Ministerio de Educación y Ciencia, Madrid.; Fa 1991: 20Fa J.E. 1991. Conservación de los Ecosistemas Forestales de Guinea Ecuatorial. IUCN, Gland, Cambridge.). However, these figures vary greatly from one year to another, with an estimated mean precipitation of 2500 mm/year (Wilks & Issembé 2000: 3Wilks C. & Issembé Y. 2000. Les arbres de la Guinée Equatoriale: Guide pratique d’identification: région continentale. Projet CUREF, Bata.). Rainfall decreases from west to east and from south to north. Mountainous areas, such as Mount Mitra, and the basin drained by the Mitemele river (Utamboni), on the southern border with Gabon, are the most humid areas.
Botanical collectors in Río Muni
⌅The mainland of Equatorial Guinea has been much less explored than the island territories. The first known collections were made by the German Gustaf Mann (1836-1916), expeditionary of the Baikie’s Niger Expedition. Although he focused his work on Bioko, he also collected fifty specimens in Litoral province (Corisco, Elobey, and in the Kongui river [Congüe]) in 1862. These specimens are preserved mainly in the K herbarium.
It took almost half a century for the explorations in this area to continue, carried out by another German explorer, Günther Tessmann (1884-1969), who in 1908 collected 100 specimens in Litoral province and especially in Wele Nzas (hosted at K), at the Nkolentangan (Alén), Uelleburg and Bebai stations. In 1928, the Spanish forestry engineer Fernando Nájera, commissioned by the “Dirección General de Marruecos y Colonias”, visited the continental area to study the forest richness of Spanish Guinea. During the four months that he stayed in Río Muni, he studied and identified around 60 types of wood. These collections were probably lost from the Madrid “Escuela de Ingenieros de Montes” due to a fire. The result of Nájera’s study was published by the “Instituto Forestal de Investigaciones y Experiencias” (Nájera 1930Nájera F. 1930. La Guinea española y su riqueza forestal. Instituto forestal de investigaciones y experiencias, Madrid.).
The history of Spanish botanical collections in the continental region begins with the pharmaceutical inspector Lope del Val Cordón (1896-1967), who visited the area between June and July 1939, collecting 650 specimens in the four continental provinces. The first botanist to take a decided interest in the flora of Equatorial Guinea was Emilio Guinea López (1907-1985). He made only one trip to the continent between June and September 1945. Guinea indicates that he collected 3,000 specimens. This number is difficult to confirm due to the complicated numbering system that he used. What we know for sure is that more than 1000 vouchers are preserved in MA. A part of these specimens is found in Lisbon (LISC), where Emilio Guinea traveled to identify this material, and perhaps in London (K). The itinerary of his trip shows that he traveled through most of the continental region, with long walking journeys through the most intricate of the tropical forest. Although he collected in the four provinces, it is noteworthy his systematic and intense tours to the Wele Nzas and Kie Ntem provinces. A first advance of his work was published in the Anales del Jardín Botánico de Madrid (Guinea 1945Guinea E. 1945. Novedades sistemáticas de mi primer viaje a la Guinea Continental Española (verano de 1945). Anales del Jardín Botánico de Madrid 6: 463-486.). The following year he published what is still today the main work on the flora of Río Muni: Ensayo Geobotánico de la Guinea Continental española (Guinea 1946Guinea E. 1946. Ensayo geobotánico de la Guinea Continental Española. Dirección General de Marruecos y Colonias, Madrid.). Guinea was occasionally accompanied by J. Gómez Moreno. It will be almost fifty years after (1946Guinea E. 1946. Ensayo geobotánico de la Guinea Continental Española. Dirección General de Marruecos y Colonias, Madrid.), before floristic studies were resumed in the continental region starting in 1990. The Spanish-Portuguese Manuel Fidalgo do Carvalho, who had already collected in Bioko, moved his residence from Malabo (Bioko) to Bata on April 10, 1991, although he had already made some collections in Río Muni in December 1990. Carvalho remained on the continent until September of 1997. During his time in Río Muni, he made 1896 botanical collections. The abundant material that he collected from each specimen is very remarkable, always from fertile plants, and perfectly prepared and preserved. A complete series of his collections is held in MA, with numerous duplicates in major European and North American herbaria (AAU, B, BM, BR, COI, FI, G, H, K, LG, LISC, MO, NY, P, S, UPS, US, WAG, etc.) as well as in the National Herbarium of Equatorial Guinea (BATA).
At the same time of Guinea’s collecting work, in the 90s, the CUREF (“Conservación y Utilización Racional de los Ecosistemas Forestales de Guinea Ecuatorial”) project, funded by the European Union, started, with special emphasis on the study of plants. The botanical leader of the project was Jean Lejoly (BRLU) with the invaluable help of Stanislaw Lisowski (POZG). Several European botanists collected with the support of this project: Tariq Stévart (BRLU, MO), Ingrid Parmentier (BRLU), Bruno Senterre (BRLU) and Stephan Porembski (ROST) who collaborated in the training of a group of Guinean botanists from the INDEFOR (“Instituto de Desarrollo Forestal”), under the newly created BATA herbarium: Crisantos Obama, Pablo Esono, Norberto Nguema, Ildefonso Ndong, Domingo Ngomo, Francisca Eneme, and Diosdado Obiang Mbomio. In addition, there were six additional plant collectors who sometimes accompanied the CUREF-INDEFOR collecting team: Pierre van Asbroeck (BRLU) who collected in 1998 with Lejoly; N. Biedinger (BRLU) in 1998 with Porembski and N. Nguema, and Elad Maurice Epah (BRLU) in 1998 with Lejoly.
In 1997, with the financial support, of the “Agencia Española de Cooperación Internacional y Desarrollo” first, and later the Spanish Ministerio de Ciencia (in their different denominations), the Real Jardín Botánico, CSIC, began a project to study the flora of Equatorial Guinea, including Río Muni, Bioko and Annobón. It was directed by Mauricio Velayos (1955-) from the Real Jardín Botánico, CSIC. Since then, apart from M. Velayos, a team of researchers participated and directed the exploration and collection trips through the four continental provinces: C. Aedo (MA), F.J. Cabezas (MA, currently at MACB), M. de la Estrella (MA, currently at COA), P. Barberá (MA, currently at MO) and M. Fero Meñe (MA, currently at UNGE). In total, 6,800 specimens were collected under the Flora of Equatorial Guinea project.
Other people also participated in plant collecting campaigns organized by the Real Jardín Botánico: Raquel Pérez-Viso, who lived in Bata between 1998 and 2000 and collected intensively in Río Muni (4,500 specimens, especially from the Centro Sur Province). Myriam López Serrano, a pharmacist from Granada, focused on the study of the traditional use of medicinal plants of the Centro Sur Province. Encarnación Gómez Marín and Laureano Merino Cristóbal collected 160 plant specimens for the publication of the book Plantas Medicinales de Guinea Ecuatorial. Up to 48 more botanists visited Equatorial Guinea sporadically and collected in the country, but all together collected less than 100 specimens.
Floristic knowledge
⌅Most recent published data from Río Muni are those of Sosef & al. (2017)Sosef M.S., Dauby G., Blach-Overgaard A., van der Burgt X., Catarino L., Damen T., Deblauwe V., Dessein S., Dransfield J., Droissart V., Duarte M.C., Engledow H., Fadeur G., Figueira R., Gereau R.E., Hardy O.J., Harris D.J., de Heij J., Janssens S., Klomberg Y., Klomberg Y., Ley A.C., Mackinder B.A., Meerts P., de Poel J.L. van, Sonke B., Stevart T., Stoffelen P., Svenning J.C., Sepulchre P., Zaiss R., Wieringa J.J. & Couvreur T.L. 2017. Exploring the floristic diversity of tropical Africa. BMC biology 15: 15.. In this study, the reported plant species richness for the whole of Equatorial Guinea is 3,049 species, increasing the estimated figure up to 3,821 species. This approach was based on the study of 15,341 records reflecting a Collection Density Index (CDI) for the country (number of collections/100 km2) of 54.69 (Campbell 1989Campbell D.G. 1989. The Importance of Floristic Inventory in the Tropics. In Campbell D.G. & Hammond D. (eds.), Floristic inventory of tropical countries: The status of plant systematics, collections, and vegetation, plus recommendations for the future: 6-29. New York Botanical Garden, Nueva York.). When CDI is calculated, the figures reveal a moderate level of knowledge of the region and more precisely from the continental region. These authors suggest a minimum of a CDI of 100 before one can state that the botanical inventory of a country or a region is of an acceptable level. If we calculate the CDI of the four provinces of Río Muni, only the Litoral Province is near the level of the CDI of 100, being Kie Ntem and Wele Nzas the provinces with the lowest botanical knowledge (Table 1).
| Territory | Nº collections | Area km² | CDI |
|---|---|---|---|
| Centro Sur | 4,065 | 9,931 | 40 |
| Kie Ntem | 1,019 | 3,943 | 27 |
| Litoral | 4,953 | 6,665 | 74 |
| Wele Nzas | 1,295 | 5,478 | 23 |
| Unknown territory | 217 | - | - |
| Total Río Muni | 11,549 | 26,017 | 44 |
If we plot the collection localities from the 23,517 specimen records (Fig. 1) we observed that plant-collecting efforts are geographically biased and some inaccessible places remain poorly known, thus botanical exploration in Río Muni is still one of the main tasks for future biodiversity studies.
MATERIAL AND METHODS
⌅We built a checklist (Appendix 1) based primarily on both herbarium specimens and bibliographic references. We studied 11,549 specimens collected in Río Muni, mainly from the herbaria BATA, BRLU, HBG, K, LBV, MA, and WAG; although to a lesser extent, also from BM, BR, G, MO, NY, P, and S. For comparative purposes specimens from Cameroon, Gabon, São Tomé and Príncipe, and other territories of Equatorial Guinea kept in those herbaria were also studied.
Of the 11,549 specimens compiled, only 6,850 could be identified to species, this is, assigned to an accepted name. Bibliographic references for all families of vascular plants were also checked. In total 7,985 species records from bibliographic sources were compiled from Alston (1956Alston A.H.G. 1956. New African ferns. Boletim da Sociedade Broteriana, sér. 2, 2: 30: 5-27., 1959)Alston A.H.G. 1959. The ferns and fern-allies of West Tropical Africa. A Supplement of the second edition of the Flora of West Tropical Africa. Crown Agents, London., Arends (1992)Arends J.C. 1992. Studies in Begoniaceae IV. Biosystematics of Begonia squamulosa Hook.f. and affiliated species in section Tetraphila A.DC. Wageningen Agricultural University Papers 91(6): 1-222., Aubréville (1961)Aubréville A. 1961. Sapotacées. In Aubréville A. (ed.), Flore du Gabon 1: 1-162. Muséum National d´Histoire Naturelle, Paris., Aubriot (2020)Aubriot X. 2020. Solanaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 55: 89-137. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf. , Bamps (1970Bamps P. 1970. Notes sur les Guttiferae d’Afrique tropicale. VI et VII. Bulletin du Jardin Botanique National de Belgique 40: 281-290., 1974)Bamps P. 1974. Contribution a l’etude des Araliacees africaines. Bulletin du Jardin Botanique National de Belgique 44: 101-139., Barberá & al. (2013Barberá P., Aedo C. & Velayos M. 2013. Annotated checklist and identification keys of the Acalyphoideae (Euphorbiaceae) of Equatorial Guinea (Annobón, Bioko and Río Muni). Phytotaxa 140: 1-25., 2014Barberá P., Velayos M. & Aedo C. 2014. Taxonomic Revision of Grossera (Crotonoideae, Euphorbiaceae): A Central African Genus. Systematic Botany 39: 490-509. , 2015)Barbera P., Riina R. & Velayos M. 2015. A new species of Grossera (Euphorbiaceae) from Equatorial Guinea. Phytotaxa 221: 175-180., Bauters & al. (2018)Bauters K., Goetghebeur P., Asselman P., Meganck K. & Larridon I. 2018. Molecular phylogenetic study of Scleria subgenus Hypoporum (Sclerieae, Cyperoideae, Cyperaceae) reveals several species new to science. PLOS ONE 13: e0203478., Bidault & van der Burg (2019)Bidault E. & van der Burg W.J. 2019. Novitates Gabonenses 90: Palisota (Commelinaceae) revisited: description of eight new species from Central Africa and notes on the identity of P. satabiei and P. bogneri. Candollea 74: 169-202., Bissiengou & al. (2013)Bissiengou P., Chatrou L.W., Wieringa J.J. & Sosef M.S.M. 2013. Taxonomic novelties in the genus Campylospermum (Ochnaceae). Blumea Journal of Plant Taxonomy and Plant Geography 58: 1-7., Biye et al. (2014)Biye E.H., Balkwill K. & Cron G.V. 2014. A clarification of Gnetum L. (Gnetaceae) in Africa and the description of two new species. Plant Systematics and Evolution 300: 263-272. , Bos (1984)Bos J.J. 1984. Dracaena in West Africa. Wageningen Agricultural University Papers 84 (1): 1-126., Bourobou (2018)Bourobou H.P. 2018. Onagraceae. In Sosef S.M. & al. (eds.), Flore du Gabon 55: 21-35. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf. , Brenan (1953aBrenan J.P.M. 1953a. Plants on the Cambridge Expedition, 1947-1948: III. Kew Bulletin 7: 441-457., 1953bBrenan J.P.M. 1953b. The Albizzia gummifera complex. Kew Bulletin 7: 507-537., 1953cBrenan J.P.M. 1953c. Vernonia titanophylla. In Tropical African Plants: XXIII”. Kew Bulletin 8: 116-117., 1968)Brenan J.P.M. 1968. Commelinaceae. In Hutchinson J. & Dalziel J.M. (eds.), Flora of West Tropical Africa, ed. 2, 3: 22-50. Crown Agents for Overseas Governments and Administrations, London. , Brenan & Exell (1957)Brenan J.P.M. & Exell A.W. 1957. Acacia pennata (L.) Willd. and its relatives in Tropical Africa. Boletim da Sociedade Broteriana, sér. 2, 31: 99-140., Breteler (1999Breteler F.J. 1999. A revision of Prioria, including Gossweilerodendron, Kingiodendron, Oxystigma, and Pterygopodium (Leguminosae-Caesalpinoideae-Detarieae) with emphasis on Africa. Wageningen Agricultural University Papers 99 (3): 1-61., 2010Breteler F.J. 2010. Revision of the African genus Anthonotha (Leguminosae, Caesalpinioideae). Plant Ecology and Evolution 143: 70-99., 2011Breteler F.J. 2011. Thecacoris, including Cyathogyne (Phyllanthaceae), in West Africa: generic delimitation, description of a new species, and a synopsis of all West African species. Edinburgh Journal of Botany 68: 343-350., 2013Breteler F.J. 2013. Revision of Calycobolus (Convolvulaceae) in continental Africa. Plant Ecology and Evolution 146: 328-350., 2016Breteler F.J. 2016. Leptoderris. In Sosef S.M. & al. (eds.), Flore du Gabon 49: 217-230. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf., 2017Breteler F.J. 2017. Anacardiaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 50: 1-50. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf., 2018)Breteler F.J. 2018. Revision of the African genus Crotonogyne (Euphorbiaceae). Plant Ecology and Evolution 151: 352-379., Breteler & Smissaert-Houwing (1977)Breteler F.J. & Smissaert-Houwing A.A.S. 1977. Revision of Atroxima Stapf and Carpolobia G.Don (Polygalaceae). Mededelingen Landbouwhogeschool Wageningen 77(18): 1-45., Cabezas & al. (2004Cabezas F., Aedo C. & Velayos M. 2004. Checklist of the Cyperaceae of Equatorial Guinea. Belgian Journal of Botany 137: 3-26., 2005Cabezas F., Estrella M., Aedo C. & Velayos M. 2005. Marantaceae of Equatorial Guinea. Annales Botanici Fennici 42: 173-184. , 2009)Cabezas F., Estrella M., Aedo C. & Velayos M. 2009. Checklist of Commelinaceae of Equatorial Guinea (Annobón, Bioko and Río Muni). Botanical Journal of the Linnean Society 159: 106-122. , Cebolla-Lozano & Rivas-Ponce (1995a)Cebolla-Lozano C. & Rivas-Ponce M.A. 1995. Poaceae Guineae Aequatorialis nonnullae, II. Fontqueria 42:19-22. , Chatrou & Repetur (1998)Chatrou L.W. & Repetur C.P. 1998. Preliminary notes on a revision of Letestudoxa, Pseudartabotrys, and the tranfer of Pachypodanthium to Duguetia. In Chatrou L.W., Changing genera: systematic studies in Neotropical and West African Annonaceae: 63-81. Ph.D. dissertation, Utrecht University, Utrecht. , Couvreur (2008Couvreur T.L.P. 2008. Revealing the secret of African Annonaceae. Systematics, evolution and biogeography of the syncarpus Genera Isolona and Monodora. Ph.D. dissertation, Wageningen University, Wageningen., 2009)Couvreur T.L.P. 2009. Monograph of the syncarpous African genera Isolona and Monodora (Annonaceae). Systematic Botany Monographs 87: 1-150. , Cufodontis (1953Cufodontis G. 1953. Enumeratio Plantarum Aethiopiae Spermatophyta. Bulletin du Jardin Botanique de l’État à Bruxelles 23(3-4): 1-112., 1955aCufodontis G. 1955a. Enumeratio Plantarum Aethiopiae Spermatophyta (Sequentia). Bulletin du Jardin Botanique de l’État à Bruxelles 25: 193-272. , 1955bCufodontis G. 1955b. Enumeratio Plantarum Aethiopiae Spermatophyta (Sequentia). Bulletin du Jardin Botanique de l’État à Bruxelles 25: 273-344., 1970)Cufodontis G. 1970. Enumeratio Plantarum Aethiopiae Spermatophyta (Sequentia). Bulletin du Jardin Botanique de l’État à Bruxelles 40: 1388-1482., Damen & al. (2018)Damen T.H.J., van der Burg W.J., Wiland-Szymańska J. & Sosef M.S.M. 2018. Taxonomic novelties in African Dracaena (Dracaenaceae). Blumea Journal of Plant Taxonomy and Plant Geography 63: 31-53 , De Kok (2022)De Kok R.P.J. 2022. Verbenaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 58: 125-140. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf. , Dekker (1983)Dekker A.J.F.M. 1983. A revision of the genera Penianthus Miers and Sphenocentrum Pierre (Menispermaceae) of West and Central Africa. Bulletin du Jardin Botanique National de Belgique 53(1-2): 17-66., Del Val (1942)Del Val L. 1942. Guinea Española. Estudios sobre su flora. Dirección General de Marruecos y colonias, Madrid., Dhetchuvi & al. (2011)Dhetchuvi J.B., Wortley A.H. & Harris D.J. 2011. A new species of Aframomum (Zingiberaceae) from Central Africa. Phytotaxa 28: 31-34., Diels (1910)Diels L. 1910. Menispermaceae. In Engler A. (ed.), Pflanzenreich [Heft 46]. IV. 94. Wilhelm Engelmann, Leipzig. , Dilst (1995)Dilst F.J.H. van 1995. Baissea A.DC. Series of revisions of Apocynaceae XXXIX. Bulletin du Jardin Botanique National de Belgique 64: 89-178., Dilst & Leeuwenberg (1991)Dilst F.J.H. van & Leeuwenberg A.J.M. 1991. Rauvolfia L. in Africa and Madagascar. Series of revisions of Apocynaceae XXXIII. Bulletin du Jardin Botanique National de Belgique 61: 21-69., Droissart & al. (2009)Droissart V., Sonké B., Nguembou C.K., Djuikouo M.N., Parmentier I. & Stévart T. 2009. Synopsis of the genus Chamaeangis (Orchidaceae), including two new taxa. Systematic Botany 34: 285-296., Eimunjeze (1976Eimunjeze V.E. 1976. A revision of Hemandradenia Stapf (Connaraceae). Mededelingen Landbouwhogeschool Wageningen 76(9): 1-34., 1989)Eimunjeze V.E. 1989. Hemandradenia Stapf. In Breteler F.J., The Connaraceae. A taxonomic study with emphasis on Africa. Wageningen Agricultural University Papers 89 (6): 275-283. , Engler (1912)Engler A. 1912. Aristolochiaceae africanae II. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 46: 412-414., Estrella & al. (2005Estrella M., Cabezas F., Aedo C. & Velayos M. 2005. Checklist of the Mimosoideae (Leguminosae) of Equatorial Guinea (Annobón, Bioko, Río Muni). Belgian Journal of Botany 138: 11-23. , 2006Estrella M., Cabezas F., Aedo C. & Velayos M. 2006. Checklist of the Caesalpinioideae (Leguminosae) of Equatorial Guinea (Annobón, Bioko, Río Muni). Botanical Journal of the Linnean Society 151: 541-562., 2010aEstrella M., Cabezas F., Aedo C. & Velayos M. 2010a. The Papilionoideae (Leguminosae) of Equatorial Guinea (Annobón, Bioko and Río Muni). Folia Geobotanica 45: 1-57., 2010b)Estrella M., Aedo C., Mackinder B. & Velayos M. 2010b. Taxonomic Revision of Daniellia (Leguminosae: Caesalpinioideae). Systematic Botany 35: 296-324., Fernández-Casas (1992)Fernández-Casas F.J. 1992. Ad Guineae Aequatorialis floram texendam inventa varia. Fontqueria 33: 33-85., Fero (2012)Fero M. 2012. Magnoliidae, Nymphaeidae y Ranunculidae de Guinea Ecuatorial y revisión taxonómica del género Neostenanthera Exell (Annonaceae). Ph.D. dissertation, Universidad Complutense de Madrid, Madrid., Fero & al. (2003Fero M., Cabezas F., Aedo C. & Velayos M. 2003. Check-List of the Piperaceae of Equatorial Guinea. Anales del Jardín Botánico de Madrid 60: 45-50., 2014)Fero M., Aedo C., Cabezas F. & Velayos M. 2014. Taxonomic Revision of Neostenanthera (Annonaceae). Systematic Botany 39: 17-30. , Figueiredo (1995)Figueiredo E. 1995. A revision of Lasiodiscus (Rhamnaceae). Kew Bulletin 50: 495-526., Fischer & Lachenaud (2013)Fischer E. & Lachenaud O. 2013. A new species of Torenia (Linderniaceae) from Gabon, remarks on Torenia mannii Skan, and a key to the African and Madagascan Torenia species. Phytotaxa 125: 40-46., Galán Cela & al. (2018)Galán Cela P., Gamarra R. & Ortúñez E. 2018. Catálogo de la familia Orchidaceae en Guinea Ecuatorial. Collectanea Botanica 37: e003., Gautier & al. (2016)Gautier L., Lachenaud O., van der Burgt X. & Kenfack D. 2016. Five new species of Englerophytum K. Krause (Sapotaceae) from central Africa. Candollea 71: 287-305., Geerinck (1980)Geerinck D. 1980. Répartition géographique d’Orchidacées africaines. I: Polystachya Hook. Bulletin du Jardin Botanique National de Belgique 50: 99-116., Ghogue & al. (2017)Ghogue J.P., Sonké B. & Couvreur T.L.P. 2017. Taxonomic revision of the African genera Brieya and Piptostigma (Annonaceae). Plant Ecology and Evolution 150: 173-216. , González Gómez & Pereira (1946)González Gómez C. & Pereira A.J. 1946. Investigaciones sobre las semillas de Caloncoba mannii (Oliv.) Gilg, de la Guinea Española. Anales del Jardín Botánico de Madrid 6: 110-122., Guinea (1945Guinea E. 1945. Novedades sistemáticas de mi primer viaje a la Guinea Continental Española (verano de 1945). Anales del Jardín Botánico de Madrid 6: 463-486., 1946Guinea E. 1946. Ensayo geobotánico de la Guinea Continental Española. Dirección General de Marruecos y Colonias, Madrid., 1951)Guinea E. 1951. Melastomataceae Fernandopoanae. Boletín de la Real Sociedad Española de Historia Natural, Sección Biológica 49: 175-187., Harris (1995)Harris D.J. 1995. A revision of the Irvingiaceae in Africa. Bulletin du Jardin Botanique National de Belgique 65: 143-196., Harris & Wortley (2018)Harris D.J. & Wortley A.H. 2018. Monograph of Aframomum (Zingiberaceae). Systematic Botany Monographs 104: 1-204., Harris & al. (2021)Harris D.J., Barberá P., Nguem D. & Quintanar A. 2021. Putranjivaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 57: 107-160. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf., Hauman (1951)Hauman L. 1951. Nymphaeaceae. In Robyns & al. (eds.), Flore du Congo Belge et du Ruanda-Urundi vol. 2: 153-164. Publications de l’Institut National pour l’Étude Agronomique du Congo Belge (I.N.E.A.C.), Bruxelles., Heine (1966)Heine H. 1966. Révision du genre Thomandersia Baill. (Acanthaceae). Bulletin du Jardin Botanique de l’État à Bruxelles 36: 207-248., Hepper (1954Hepper F.N. 1954. Flora of West Tropical Africa, ed. 2, 1(1). The Crown agents for Oversea Governments and Administrations, London. , 1958Hepper F.N. 1958. Flora of West Tropical Africa, ed. 2, 1(2). The Crown agents for Oversea Governments and Administrations, London. , 1963Hepper F.N. 1963. Flora of West Tropical Africa, ed. 2, 2. The Crown agents for Oversea Governments and Administrations, London. , 1968aHepper F.N. 1968a. Flora of West Tropical Africa, ed. 2, 3(1). The Crown agents for Oversea Governments and Administrations, London. , 1968bHepper F.N. 1968b. Notes on Tropical African Monocotyledons: I. Kew Bulletin 21: 491-498., 1968cHepper F.N. 1968c. Marantaceae. In Hutchinson J. & Dalziel J.M. (ed.), Flora of West Tropical Africa, the British West African colonies, British Cameroons, the French and Portugese Colonies south of the tropic of Cancer to Lake Chad, and Fernando Po, ed. 2, vol. 3(1): 79-89, Crown Agents for Oversea Governments and Administrations, London., 1972)Hepper F.N. 1972. Flora of West Tropical Africa, ed. 2, 3(2). The Crown agents for Oversea Governments and Administrations, London., Holttum (1981Holttum R.E. 1981. The tree-ferns of Africa Kew Bulletin 36(3): 463-482. , 1986)Holttum R.E. 1986. Studies in the fern-genera allied to Tectaria V. Triplophyllum, a new genus of Africa and America Kew Bulletin 41: 237-260., Hooker (1864)Hooker J.D. 1864. On the plants of the temperate regions of the Cameroons Mountains and Islands in the Bright of Benin; collected by Mr. Gustav Mann, government botanist. Journal of the Proceedings of the Linnean Society, Botany 7: 171-240., Hooper & Napper (1972)Hooper S.S. & Napper D.M. 1972. Cyperaceae. In Hutchinson J. & Dalziel J.M. (ed.), Flora of West Tropical Africa, the British West African colonies, British Cameroons, the French and Portuguese Colonies south of the tropic of Cancer to Lake Chad, and Fernando Po, ed. 2, vol. 3(2): 278-349. Crown Agents for Oversea Governments and Administrations, London., Hutchinson & Dalziel (1927Hutchinson J. & Dalziel J.M. 1927. Flora of West Tropical Africa ed. 1, 1 (1). The Crown agents for the colonies, London. , 1928Hutchinson J. & Dalziel J.M. 1928. Flora of West Tropical Africa ed. 1, 1 (2). The Crown agents for the colonies, London. , 1931Hutchinson J. & Dalziel J.M. 1931. Flora of West Tropical Africa ed. 1, 2 (1). The Crown agents for the colonies, London., 1936)Hutchinson J. & Dalziel J.M. 1936. Flora of West Tropical Africa ed. 1, 2 (2). The Crown agents for the colonies, London. , Ikabanga & al. (2019)Ikabanga D.U., Koffi K.G., Onana J.M., M’batchi B., Hardy O.J. & Stévart T. 2019. Révision taxonomique du genre Santiria (Burseraceae) en Afrique tropicale. Candollea 74: 115-130 , Jacques-Félix (1976Jacques-Félix H. 1976. Le genre Tristemma Jussieu (Melastomataceae). Bulletin du Muséum National d’Histoire Naturelle, sér. 3, Botanique 28: 137-207., 1981)Jacques-Félix H. 1981. Révision du genre Calvoa (Melastomataceae). Bulletin du Muséum National d’Histoire Naturelle, Paris, 4º sér., 3, section B, Adansonia 2: 123-143., Jeffrey (1966Jeffrey C. 1966. Notes on Compositae: I. The Cichorieae in East Tropical Africa. Kew Bulletin 18: 427-486., 1986Jeffrey C. 1986. The Senecioneae in East Tropical Africa. Notes on Compositae: IV. Kew Bulletin 41: 873-943., 1997)Jeffrey C. 1997. What is Emilia coccinea (Sims) G.Don (Compositae)? A revision of the large-headed Emilia species of Africa Kew Bulletin 52: 205-212., Johnson & Murray (2018)Johnson D.M. & Murray N.A. 2018. A revision of Xylopia L. (Annonaceae): the species of Tropical Africa. PhytoKeys 97: 1-252., Jongkind & Lachenaud (2019)Jongkind C.C.H. & Lachenaud O. 2019. Vadensea (Icacinaceae), a new genus to accommodate continental Africa species of Desmostachys. Phytotaxa 405: 237-247, Jongkind (1989aJongkind C.C.H. 1989a. Agelaea Sol. ex Planchon. In Breteler F.J. (ed.), The Connaraceae. A taxonomic study with emphasis on Africa. Wageningen Agricultural University Papers 89 (6): 136-168., 1989bJongkind C.C.H. 1989b. Manotes Sol. ex Planchon. In Breteler F.J. (ed.), The Connaraceae. A taxonomic study with emphasis on Africa. Wageningen Agricultural University Papers 89 (6): 294-309., 1989cJongkind C.C.H. 1989c. Rourea Aublet. In Breteler (ed.), The Connaraceae. A taxonomic study with emphasis on Africa. Wageningen Agricultural University Papers 89(6): 310-368., 2022)Jongkind C.C.H. 2022. Apocynaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 59: 1-276. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf., Keay (1952)Keay R.W.J. 1952. Revision of the “Flora of West Tropical Africa” - I. Kew Bulletin 7: 149-165., Kenfack & al. (2015)Kenfack D., Gereau R.E., Thomas D.W. & Sainge M.N. 2015. The tropical African genus Crotonogynopsis (Euphorbiaceae) with two new species. Novon 24: 246-255., Koechlin (1965)Koechlin J. 1965. Scitaminales: Musacées, Strélitziacées, Zingibéracées, Cannacées, Marantacées. In Aubreville A. (ed.), Flore du Cameroun 4: 27-41. Muséum National d’Historie Naturelle, Paris., Kruif de (1985)Kruif A.P.M. de 1985. A revision of Oncinotis Benth. (Apocynaceae). Part XVI. Agricultural University Wageningen Papers 85-2: 5-45, Lachenaud (2016aLachenaud O. 2016a. Dalbergia. In Sosef S.M. & al. (eds.), Flore du Gabon 49: 101-153. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf., 2016bLachenaud O. 2016b. Millettia sect. Afroscandentes. In Sosef S.M. & al. (eds.), Flore du Gabon 49: 251-260. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf., 2019)Lachenaud O. 2019. Révision du genre Psychotria (Rubiaceae) en Afrique occidentale et centrale. Opera Botanica Belgica 17: 1-909., Lachenaud & Breteler (2011)Lachenaud O. & Breteler F.J. 2011. Novitates Gabonenses 76. Un nouveau Maesobotrya (Euphorbiaceae) des Monts de Cristal (Gabon et Guinée Équatoriale). Adansonia, sér. 3, 33: 215-219., Lachenaud & Jongkind (2010)Lachenaud O. & Jongkind C. 2010. Three new or little-known Chassalia (Rubiaceae) species from west and central Africa. Nordic Journal of Botany 28: 13-20., Lachenaud & van der Maesen (2016)Lachenaud O. & van der Maesen L.J.G. 2016. Notes on African Dalbergia (Leguminosae-Papilionoideae) with the description of two new species from Atlantic Central Africa. Symbolae Botanicae Upsalienses 38: 167-194., Lachenaud & al. (2013Lachenaud O., Droissart V., Dessein S., Stévart T., Simo M., Lemaire B., Taedoumg H. & Sonké B. 2013. New records for the flora of Cameroon, including a new species of Psychotria (Rubiaceae) and range extensions for some rare species. Plant Ecology and Evolution 146: 121-133., 2017Lachenaud O., Schatz G.E., Dauby G. & Stévart T. 2017. Two new species of Diospyros (Ebenaceae) from Central Africa. Plant Ecology and Evolution 150: 217-224., 2018)Lachenaud O., Stévart T., Boupoya A., Texier N., Dauby G. & Bidault E. 2018. Novitates Gabunensis 88: additions to the flora of Gabon and new records of little-known species. Plant Ecology and Evolution 151: 393-422., Le Thomas (1969)Le Thomas A. 1969). Annonacées. In Aubréville A. (ed.), Flore du Gabon 16: 1-372. Muséum National d’Histoire Naturelle, Paris., Leal (2007)Leal M.E. 2007. Novitates Rio Munis 1. A new endemic Scaphopetalum (Malvaceae) from Mount Mitra, Equatorial Guinea. Blumea Journal of Plant Taxonomy and Plant Geography 52: 137-138. , Leeuwenberg (1961aLeeuwenberg A.J.M. 1961a. The Loganiaceae of Africa II. A revision of Mostuea Didr. Mededelingen Landbouwhogeschool Wageningen 61(4): 1-31., 1961bLeeuwenberg A.J.M. 1961b. The Loganiaceae of Africa I. Anthocleista. Acta Botanica Neerlandica 10: 1-53. , 1969Leeuwenberg A.J.M. 1969. The Loganiaceae of Africa VIII. Strychnos III. Revision of the African species with notes on the extra-African. Mededelingen Landbouwhogeschool Wageningen 69: 1-316., 1985)Leeuwenberg A.J.M. 1985. Voacanga Thou. In Leeuwenberg A.J.M. (ed.), Series of revisions of Apocynaceae XV. Agricultural University Wageningen Papers 85 (3): 5-80., Lejoly & Lisowski (1998Lejoly J. & Lisowski S. 1998. Catalogue des Plantes Vasculaires de la Region Continentale de Guinee Equatorial. Ministerio de Bosques y Medio Ambiente República de Guinea Ecuatorial. CUREF, Bata., 1999aLejoly J. & Lisowski S. 1999a. Novitates Guineae Aequatorialis, 1-5. Bulletin du Jardin Botanique National de Belgique 67: 99-121. , 1999bLejoly J. & Lisowski S. 1999b. Novitatis Guineae Aequatorialis (6) Heterotis obamae (Melastomataceae) espèce nouvelle du Rio Muni. Systematics and Geography of Plants 69: 185-188. , 2000)Lejoly J. & Lisowski S. 2000. Novitates Guineae Aequatorialis (7): Lobelia sylvicola (Lobeliaceae), espèce nouvelle de l’Afrique équatoriale occidentale. Acta Botanica Gallica 147: 119-122., Lemmens (1989aLemmens R.H.M.J. 1989a. Cnestis Juss. In Breteler F.J. (ed.), The Connaraceae. A taxonomic study with emphasis on Africa. Wageningen Agricultural University Papers 89(6): 174-238., 1989b)Lemmens R.H.M.J. 1989b. Connarus L. In Breteler F.J. (ed.), The Connaraceae. A taxonomic study with emphasis on Africa. Wageningen Agricultural University Papers. 89(6): 239-267., Léonard (1951Léonard J. 1951. Notulae Systematicae XI. Les Cynometra et les genres voisins en Afrique tropicale. Bulletin du Jardin Botanique de l’État à Bruxelles 21(3-4): 373-450., 1955Léonard J. 1955. Notulae Systematicae XIX. Observations sur divers Bridelia africains (Euphorbiaceae). Bulletin du Jardin Botanique de l’État à Bruxelles 25: 359-374., 1961Léonard J. 1961. Notulae Systematicae XXXII. Observations sur des espèces africaines de Clutia, Ricinodendron et Sapium (Euphorbiacées). Bulletin du Jardin Botanique de l’État à Bruxelles 31: 391-406., 1988Léonard J. 1988. Révision du genre Antidesma L. (Euphorbiaceae) en Afrique Centrale. Bulletin du Jardin Botanique National de Belgique 58: 3-46., 1995Léonard J. 1995. Le genre Discoglypremna Prain au Zaïre (Euphorbiaceae). Bulletin du Jardin Botanique National de Belgique 64: 201-207., 1996)Léonard J. 1996. Révision des espèces zaïroises des genres Mareya Baill. et Mareyopsis Pax & K.Hoffm. (Euphorbiaceae). Bulletin du Jardin Botanique National de Belgique 65: 3-22., Léonard & Voorhoeve (1964)Léonard J. & Voorhoeve A.G. 1964. Notulae Systematicae XXXV. The genera Stachyothyrsus Harms and Kaoue Pellegr. (African Caesalpiniaceae). Bulletin du Jardin Botanique de l’État à Bruxelles 34: 419-423., Lissambou & al. (2018)Lissambou B.J., Hardy O.J., Atteke C., Stevart T., Dauby G., Mbatchi B., Sonké B. & Couvreur T.L.P. 2018. Taxonomic revision of the African genus Greenwayodendron (Annonaceae). PhytoKeys 114: 55-93., Lock (1978Lock J.M. 1978. Notes on the genus Aframomum (Zingiberaceae). 3. Two new species from West Africa. Bulletin du Jardin Botanique National de Belgique 48(3-4): 393-398., 1980Lock J.M. 1980. Notes on Aframomum (Zingiberaceae) in West Africa, with a new key to the species. Kew Bulletin 35: 299-313., 1989)Lock J.M. 1989. Legumes of Africa: A Check-List. Royal Botanic Gardens, Kew., Maas & Maas-van de Kamer (2020)Maas P. & Maas-van de Kamer H. 2020. Gentianaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 54: 59-80. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf., Maas-van de Kamer & al. (2016)Maas-van de Kamer H., Maas P.J.M., Wieringa J.J. & Specht C.D. 2016. Monograph of African Costaceae. Blumea Journal of Plant Taxonomy and Plant Geography 61: 280-318. , Maesen & Sosef (2016)Maesen L.J.G. & Sosef S.M. 2016. Leguminosae. In Sosef S.M. & al. (eds.), Flore du Gabon 49: 1-407. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf., Manktelow (1996)Manktelow M. 1996. Phaulopsis (Acanthaceae): a monograph. Symbolae Botanicae Upsalienses 31(2): 1-184., Mas-Guindal (1944)Mas-Guindal J. 1944. Datos para el conocimiento de la flora de la Guinea Española. La vegetación espontánea y las plantas cultivadas. Dirección General de Marruecos y Colonias, Madrid., Milne-Redhead (1950)Milne-Redhead E. 1950. Notes on African Marantaceae: I. Kew Bulletin 5: 157-164., Morales (1993Morales R. 1993. Lamiaceae Guineae Aequatorialis nonnullae. Fontqueria 36: 287-291., 2011)Morales R. 2011. Las labiadas (Lamiaceae) de Guinea Ecuatorial. Anales del Jardín Botánico de Madrid 68: 199-223., Moran & Smith (2001)Moran C.R. & Smith R.A. 2001. Phytogeographic ralationships between Neotropical and African-Madagascan Pteridophytes. Brittonia 53: 304-351., Morton (1978Morton J.K. 1978. A revision of the Justicia insularis-striata complex (Acanthaceae). Kew Bulletin 32: 433-448., 1979)Morton J.K. 1979. An overlooked species of Nelsonia (Acanthaceae) from Africa. Kew Bulletin 33: 399-402., Moutsamboté (1990)Moutsamboté J.M. 1990. Vernonia titanophylla Brenan (Asteraceae), espèce nouvelle pour la flore du Congo. Bulletin du Jardin Botanique National de Belgique 60(3-4): 275-278., Nelmes (1955Nelmes E. 1955. Notes on Cyperaceae: XXXIII. The African species of Hypolytrum. Kew Bulletin 10: 63-82., 1956Nelmes E. 1956. Notes on Cyperaceae: XXXIX. African species of Scleria excluding sect. Hypoporum. Kew Bulletin 11: 73-111., 1957)Nelmes E. 1957. Notes on Cyperaceae: XLI. Rhynchospora in Tropical East Africa. Kew Bulletin 11: 533., Ntore (2008)Ntore S. 2008. Révision du genre afrotropical Pauridiantha (Rubiaceae). Opera Botanica Belgica 15: 1-227., Oliver & Hanbury (1864)Oliver D. & Hanbury D. 1863. On some new species of Amomum from West Africa. Journal of the Proceedings of the Linnean Society, Botany 7 (26): 109-110., Oliver (1865Oliver D. 1865. On five new genera of West Tropical Africa, belonging to the natural Orders Bixineae, Tiliaceae and Annonaceae, with a note upon the genera Oncoba and Mayna. Journal of the Linnean Society, Botany 9: 170-176., 1868Oliver D. 1868. Annonaceae. In Oliver D. (ed.), Flora of Tropical Africa 1: 13-39. L. Reeve & Co., Ashford., 1871)Oliver D. 1871. Flora of tropical Africa, vol. 2, Leguminosae to Ficoideae. L. Reeve & Co., London., Parmentier (2001)Parmentier I. 2001. Premières études sur la diversité végétale des inselbergs de Guinée Équatoriale continentale. Systematics and Geography of Plants 71: 911-922., Parmentier & Geerik (2003)Parmentier I. & Geerik D. 2003. Checklist of the Melastomataceae of the Equatorial Guinea. Anales del Jardín Botánico de Madrid 60: 331-346. , Parmentier & al. (2001)Parmentier I., Lejoly J. & Nguema N. 2001. La végétation des inselbergs de Piedra Nzas (Guinée Équatoriale continentale). Acta Botanica Gallica 148: 341-365., Paton & al. (2022)Paton A., Pollard B.J. & Meerts P. 2022. Labiatae. In Sosef S.M. & al. (eds.), Flore du Gabon 58: 1-111. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf. , Pax & Hoffmann (1911Pax F. & Hoffmann K. 1911. Euphorbiaceae-Cluytieae. In Engler A. (ed.), Das Pflanzenreich IV.147.III (Heft 47), Wilhelm Engelmann, Leipzig., 1912Pax F. & Hoffmann K. 1912. Euphorbiaceae-Acalypheae-Chrozophorinae. In Engler A. (ed.), Das Pflanzenreich IV.147.VI (Heft 57). Wilhelm Engelmann, Leipzig., 1914)Pax F. & Hoffmann K. 1914. Euphorbiaceae-Acalypheae-Mercurialinae. In Engler A. (ed.), Das Pflanzenreich IV.147.VII (Heft 63) Wilhelm Engelmann, Leipzig, Berlin., Poncy (1978)Poncy O. 1978. Le genre Pararistolochia, Aristolochiaceae d’Afrique tropicale. Adansonia, sér. 2, 17: 465-494., Prain (1911)Prain D. 1911. A review of the genera Erythrococca & Micrococca. Annalen der Botanick. ed. Usteri 25: 75-638., Prance & Jongkind (2015)Prance G.T. & Jongkind C.C.H. 2015. A revision of African Lecythidaceae. Kew Bulletin 70: 1-68, Quintanar & al. (2022)Quintanar A., Barberá P. & Harris D.J. 2022. A new species of Drypetes (Putranjivaceae) from the western Congolian swamp forest, D. palustris sp. nov. Anales del Jardín Botánico de Madrid 79: e120., Rial (2002)Rial A. 2002. Une Nouvelle epèce de Macropodiella (Podostemaceae) de Guinée Équatoriale. Adansonia, sér. 3, 24: 295-297, Robbrecht & al. (1993)Robbrecht E., Rohrhofer U. & Puff C. 1993. A survey of Bertiera (Rubiaceae), including a discussion of its taxonomic position. Opera Botanica Belgica 6: 101-141, Sanford (1971)Sanford W.W. 1971. The orchid flora of Equatorial Guinea in relation to that of West Africa. Mitteilungen der Botanischen Staatssammlung München 10: 287-298., Schaefer (2021)Schaefer H. 2021. Cucurbitaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 57: 35-106. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf., Senterre (2005)Senterre B. 2005. Checklist of the Ebenaceae of Equatorial Guinea. Anales del Jardín Botánico de Madrid 62: 53-63., Simons (2021)Simons E.L.A.N. 2021. Boraginaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 57: 1-23. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf., Sleumer (1971Sleumer H. 1971. Le genre Casearia Jacq. (Flacourtiaceae) en Afrique, à Madagascar et aux Mascareignes. Bulletin du Jardin Botanique National de Belgique 41: 397-426., 1972aSleumer H. 1972a. A taxonomic revision of the genus Scottellia Oliv. (Flacourtiaceae). Blumea Journal of Plant Taxonomy and Plant Geography 20: 275-281. , 1972bSleumer H. 1972b. A taxonomic revision of the genus Dovyalis E.Mey. ex Arn. (Flacourtiaceae). Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 92: 64-89. , 1972cSleumer H. 1972c. A taxonomic revision of the genus Dasylepis Oliv. (Flacourtiaceae). Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 92: 554-561. , 1973Sleumer H. 1973. Révision du genre Homalium Jacq. (Flacourtiacées) en Afrique (y compris Madagascar et les Mascareignes). Bulletin du Jardin Botanique National de Belgique 43: 239-328., 1974aSleumer H. 1974a. Die afrikanischen Arten der Gattum Lindackeria Presl (Flacourtiaceae). Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 94: 311-326. , 1974bSleumer H. 1974b. Revision der Gattung Caloncoba Gilg (Flacourtiaceae). Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 94: 120-138. , 1974c)Sleumer H. 1974c. Revision der Gattung Poggea Gürke (Flacourtiaceae). Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 94: 296-301, Sonké (2007Sonké B., Djuikouo M.N. & Robbrecht E. 2007. Calycosiphonia pentamera sp. nov. (afrotropical Rubiaceae) from the ‘Lower Guinea’ area. Nordic Journal of Botany 25: 275-280), Sosef & Bissiengou (2016)Sosef M. & Bissiengou P. 2016. Ochnaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 48: 21-88. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf. , Sosef & Dauby (2013)Sosef M.S.M. & Dauby,G. 2013. Clusiaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 45: 1-43. Naturalis Biodiversity Center, Robdorf., Sosef & Nguema Miyono (2010)Sosef M.S.M. & Nguema Miyono N.S. 2010. New species of Begonia section Loasibegonia (Begoniaceae) from the Monte Alen region, Equatorial Guinea. Blumea Journal of Plant Taxonomy and Plant Geography 55: 91-93., Stévart & al. (2010)Stévart T., Cawoy V., Damen T. & Droissart V. 2010. Taxonomy of Atlantic Central African orchids 1. A new species of Angraecum sect. Pectinaria (Orchidaceae) from Gabon and Equatorial Guinea. Systematic Botany 35: 252-256., Stévart & Oliveira (2000)Stévart T. & de Oliveira F. 2000. Guide des Orchidées de Sao Tomé et Príncipe. ECOFAC, São Tomé., Stewart (1979)Stewart J. 1979. A revision of the African species of Aerangis (Orchidaceae). Kew Bulletin 34: 239-319., Szlachetko (2008)Szlachetko D.L. 2008. Orchidaceae of Ivory Coast. Ruizia, monografías del Real Jardín Botánico de Madrid, CSIC 20: 1-396., Thiselton-Dyer (1913)Thiselton-Dyer W.T. 1913. Flora of Tropical Africa 6 (1). L. Reeve & Co., London., Townsend (1975)Townsend C.C. 1975. The genus Celosia (Subgenus Celosia) in Tropical Africa. In Hooker´s Icon. Pl. 38(2): 1-123. , Troupin (1950Troupin G. 1950. Contribution à l’étude systématique de Berlinia Soland et genres voisins (Caesalpiniaceae - Amherstieae). Bulletin du Jardin Botanique de l’État à Bruxelles 20: 285-324, 1962)Troupin G. 1962. Monographie des Menispermaceae africaines. Mémoires de la Classe de Sciences Naturelles et Médicales, Académie royale des Sciences d’Outre-Mer 13(2): 1-320., Van der Burg (2013)Van der Burg W.J. 2013. Malvaceae. In Sosef S. & al. (eds.), Flore du Gabon 45: 45-88. Naturalis Biodiversity Center, Robdorf., Van der Burg & Bidault (2020)Van der Burg W.J. & Bidaul, E. 2020. Commelinaceae. In Sosef S.M. & al. (eds.), Flore du Gabon 55: 1-88. Naturalis Biodiversity Center & Botanic Garden Meise, Robdorf. , Velayos & al. (2001Velayos M., Aedo C. & Pérez Viso R. 2001. Check-List of the Pteridophytes of Equatorial Guinea. Belgian Journal of Botany 134: 145-191., 2008Velayos M., Aedo C., Cabezas F. & Estrella M. 2008. Flora de Guinea Ecuatorial. Claves de plantas vasculares de Annobón, Bioko y Río Muni vol. I. Psilotaceae-Vittariaceae. Real Jardín Botánico (CSIC), Madrid. , 2014Velayos M., Aedo C., Cabezas F., Estrella M., Barberá P. & Fero M. 2014. Flora de Guinea Ecuatorial. Claves de plantas vasculares de Annobón, Bioko y Río Muni vol. XI. Bromelianae-Juncanae. Real Jardín Botánico (CSIC), Madrid., 2015Velayos M., Cabezas F., Barberá P. & Fero M. 2015. Flora de Guinea Ecuatorial. Claves de plantas vasculares de Annobón, Bioko y Río Muni vol. XII. Poanae-Typhanae. Real Jardín Botánico (CSIC), Madrid., 2018)Velayos M., Cabezas F., Galán P., Gamarra R., Ortúñez E. & Fero M. 2018. Flora de Guinea Ecuatorial. Claves de plantas vasculares de Annobón, Bioko y Río Muni. Vol. X. Lilianae-Dioscoreanae. Real Jardín Botánico (CSIC), Madrid. , Veranso-Libalah & al. (2019)Veranso-Libalah M.C., Lachenaud O., Stone R.G. & Kadereit G. 2019. Nothodissotis (Melastomataceae), a new genus from Atlantic Central Africa, including the new species N. alenensis from Equatorial Guinea. PhytoKeys 118: 89-103. , Verdcourt (1996)Verdcourt B. 1996. Piperaceae. In Polhill R.M. (ed.), Flora of Tropical East Africa: 1-24. A.A. Balkema, Rotterdam and Brookfield., Vermeulen (1987)Vermeulen J.J. 1987. A taxonomic revision of the continental African Bulbophyllinae. Orchids Monographs 2: 1-298., Verstraete & al. (2013)Verstraete B., Lachenaud O., Smets E., Dessein S. & Sonké B. 2013. Taxonomy and phylogenetics of Cuviera (Rubiaceae-Vanguerieae) and reinstatement of Globulostylis with the description of three new species. Botanical Journal of the Linnean Society 173: 407-441., Villiers (1990)Villiers J.F. 1990. Contribution à l’étude du genre Newtonia Baillon (Leguminosae-Mimosoideae) en Afrique. Bulletin du Jardin Botanique National de Belgique 60: 119-138, White (1963White F. 1963. Notes on the Ebenaceae V. Some new names and new species in Diospyros. Bulletin du Jardin Botanique de l’État à Bruxelles 33: 345-367., 1976White F. 1976. The taxonomy, ecology and chorology of African Chrysobalanaceae (excluding Acioa). Bulletin du Jardin Botanique National de Belgique 46: 265-350., 1978)White F. 1978. The taxonomy, ecology and chorology of African Ebenaceae I. The Guineo-Congolian species. Bulletin du Jardin Botanique National de Belgique 48: 245-358., Whitmore (2008)Whitmore T.C. 2008. The genus Macaranga. A prodromus. Royal Botanic Gardens, Kew., Wieringa (1999)Wieringa J.J. 1999. Monopetalanthus exit. A systematic study of Aphanocalyx, Bikinia, Icuria, Michelsonia and Tetraberlinia (Leguminosae, Caesalpinioideae). Wageningen Agricultural University Papers 99 (4): 1-320., Wilde (1968Wilde J.J.F.E. de 1968. A revision of the species of Trichilia P. Browne (Meliaceae) on the African continent. Mededelingen Landbouwhogeschool Wageningen 68(2): 1-207., 1971)Wilde W.J.J.O. de 1971. A monograph of the genus Adenia Forsk. (Passifloraceae). Mededelingen Landbouwhogeschool Wageningen 71(18): 1-281., Wilks & Issembé (2000)Wilks C. & Issembé Y. 2000. Les arbres de la Guinée Equatoriale: Guide pratique d’identification: région continentale. Projet CUREF, Bata., Zemagho & al. (2017Zemagho L., Liede-Schumann S., Lachenaud O., Dessein S. & Sonké B. 2017. Taxonomic revision of Sabicea subgenus Anisophyllae (Ixoroideae, Rubiaceae) from Tropical Africa, with four new species. Phytotaxa 293: 1-68., 2018)Zemagho L., Lachenaud O. & Sonké B. 2018. Four new species of Sabicea (Rubiaceae) from tropical Africa, with additional notes on the genus. Candollea 73: 277-293.. Names were updated according to the African Plant Database (https://africanplantdatabase.ch/en), or in the cases where supporting specimens were mentioned, the corresponding accepted names were assigned. Names of localities were also updated and standardized. Complementarily, 10,109 records from GBIF (2022)GBIF.org. 2022. GBIF Occurrence Download (16 Dec. 2022), https://doi.org/10.15468/dl.gpnzaa and 8,897 records from RAINBIO (Dauby & al. 2016Dauby G., Zaiss R., Blach-Overgaard A., Catarino L., Damen T., Deblauwe V., Dessin S., Dransfield J., Droissart V., Duarte M.C., Engledow H., Fadeur G., Figueira R., Gereau R.E., Hardy O.J., Harris D.J., de Heij J., Janssens S.B., Klomberg Y., Ley A.C., Mackinder B.A., Meerts P., van de Poel J.L., Sonké B., Sosef M.S.M., Stévart T., Stoffelen P., Svenning J.-C., Sepulchre P., van der Burgt X.M., Wieringa J.J. & Couvreur T.L.P. 2016. RAINBIO: a mega-database of tropical African vascular plant distributions. PhytoKeys 74: 1-18.) databases were also checked and updated, building a dataset of 36,984 species occurrence records from Río Muni, of which 23,517 were georeferenced.
The checklist was arranged in four main plant groups: Pteridophytes, Magnoliids, Monocotyledons and Eudicotyledons. Within each group, families, genera, and species were arranged alphabetically. Family classification follows PPG I (Schuettpelz & al. 2016Schuettpelz E., Schneider H., Smith A.R., Hovenkamp P., Prado J., Rouhan G., Salino A., Sundue M., Almeida T.E. , Parris B., Sessa E.B., Field A.R., Gasper A.L., Rothfels C.J., Windham M.D., Lehnert M., Dauphin B., Ebihara A., Lehtonen S., Schwartsburd P.B., Metzgar J., Zhang L.B., Kuo L.Y., Brownsey P.J., Kato M. & Arana M.D. 2016. A community-derived classification for extant lycophytes and ferns. Journal of Systematics and Evolution 54: 563-603.) for Pteridophytes and APG IV (Byng & al. 2016Byng J.W., Chase M.W., Christenhusz M.J.M., Fay M.F., Judd W.S., Mabberley D.J., Sennikov A.N., Soltis D.E., Soltis P.S. & Stevens P.F. 2016. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV. Botanical Journal of the Linnean Society 181: 1-20.) for Angiosperms. When a discrepancy with the classification of Flora de Guinea Ecuatorial (Velayos & al. 2008Velayos M., Aedo C., Cabezas F. & Estrella M. 2008. Flora de Guinea Ecuatorial. Claves de plantas vasculares de Annobón, Bioko y Río Muni vol. I. Psilotaceae-Vittariaceae. Real Jardín Botánico (CSIC), Madrid. ) was found we indicated it in brackets. Authors of plant names were abbreviated according to Brummit & Powell (1992)Brummit P.K. & Powell C.E. 1992. Authors of plant names. Royal Botanic Gardens, Kew. Londres., and to the updated version available at http://www.ipni.org/ipni/query_author.html.
Under each accepted name, we included the following information: i) the updated IUCN category (https://www.iucnredlist.org/ accessed September 2022) (NE indicates the species has not been evaluated); ii) distribution information, indicating if the species is native, endemic, subendemic (considering subendemic plants with a reduced distribution area in which most of the localities are in Río Muni), introduced, naturalized, or cultivated and also the complete distribution range with the biogeographical divisions of Takhtajan (1986)Takhtajan A. 1986. Floristic regions of the world. University of California, Berkeley.; and iii) a list of the studied specimens arranged by provinces. References from the most relevant literature were also included, but these were not considered in the floristic analysis. Taxa marked with a question mark are doubtful because of imprecise information and must be corroborated in the future.
A map (Fig. 1) and an updated and standardized list of collection localities of Río Muni is also provided (Appendix 2). A list of 665 localities was gathered, checked, and correctly spelled, and 450 localities were revised and georeferenced.
The conservation status of threatened species was assessed using the IUCN criteria (IUCN 2019). A preliminary risk of extinction assessment using the IUCN Red List categories and criteria (IUCN 2019) was carried out for the endemics and subendemic species that have not yet been published in the IUCN. Area of Occupancy (AOO) and Extent of Occurrence (EOO), estimated using a 2 × 2 km grid, were calculated using GeoCAT (2020)GeoCAT. 2020. Geospatial Conservation Assessment Tool. Royal Botanic Gardens, Kew. Website: http://geocat.kew.org [accessed 5 Nov. 2022].
RESULTS AND DISCUSSION
⌅Floristic Analysis
⌅Due to their biological importance, floristic inventories of tropical African underexplored areas are an urgent need. Despite of the huge development of communication infrastructures in the continental region of Equatorial Guinea, a large percentage of its territory is still inaccessible (Fig. 1). Besides, some of the published data are not supported by herbarium specimens, thus so much of the information available is not reliable. Many of the analyses, conservation plans, or management strategies that have been developed in African countries have been made with outdated bibliographic data and assuming complete biodiversity inventories, which are far from being so. Thus, it is quite common in these regions (tropical Africa) that when new collections are added, species numbers change drastically. Similar results are usually observed with new taxonomic treatments or systematic analyses. Endemic or threatened species are usually known from a few collections, which require new data to properly evaluate their real taxonomic status or threat level. The Río Muni Vascular Plants catalogue is a compendium of numerous cases of the above-mentioned problems.
The checklist of Vascular Plants from Río Muni comprises 178 families, 1,020 genera and 2,707 species and infraspecific taxa (Appendix 1). Pteridophytes represent the 5% of the species (142) and the 12.35% of the families of Río Muni (22). With these figures, the floristic knowledge of Río Muni, in terms of number of species, increases in 26.14% from the most recent studies (Table 2). The number of taxa considered as native is 2,411 (89.96%), 32 species (1.2%) are introduced, 36 cultivated (1.35%), and 158 (5.92%) should be considered as naturalized since they are able to establish new populations.
| Guinea 1946Guinea E. 1946. Ensayo geobotánico de la Guinea Continental Española. Dirección General de Marruecos y Colonias, Madrid. | Lejoly & Lisowski 1998Lejoly J. & Lisowski S. 1998. Catalogue des Plantes Vasculaires de la Region Continentale de Guinee Equatorial. Ministerio de Bosques y Medio Ambiente República de Guinea Ecuatorial. CUREF, Bata. | Sosef & al. 2017Sosef M.S., Dauby G., Blach-Overgaard A., van der Burgt X., Catarino L., Damen T., Deblauwe V., Dessein S., Dransfield J., Droissart V., Duarte M.C., Engledow H., Fadeur G., Figueira R., Gereau R.E., Hardy O.J., Harris D.J., de Heij J., Janssens S., Klomberg Y., Klomberg Y., Ley A.C., Mackinder B.A., Meerts P., de Poel J.L. van, Sonke B., Stevart T., Stoffelen P., Svenning J.C., Sepulchre P., Zaiss R., Wieringa J.J. & Couvreur T.L. 2017. Exploring the floristic diversity of tropical Africa. BMC biology 15: 15. | This work | |
|---|---|---|---|---|
| Pteridophyta | 52 | 53 | 133 | 142 |
| Spermatophyta | 1,064 | 1,141 | 2,013 | 2,565 |
| Total | 1,116 | 1,194 | 2,146 | 2,707 |
The most diverse families are Rubiaceae (294 species), Fabaceae (290), Orchidaceae (168) and Poaceae (105). The 10 most species-rich families are completed by Euphorbiaceae (87), Apocynaceae (85), Cyperaceae (79), Annonaceae (68), Acanthaceae (65) and Melastomataceae (61). These 10 families alone comprise about half of the species (49.22%) of Río Muni (Fig. 2).
This floristic pattern of family diversity is similar to the one found in Annobon island (Velayos & al. 2014Velayos M., Barberá P., Cabezas F., Estrella M., Fero M. & Aedo C. 2014. Checklist of the Vascular Plants of Annobón (Equatorial Guinea). Phytotaxa 171: 1-078. ). Such pattern is observed even when total species-richness figures are 10-times bigger (Annobon 24 species of Fabaceae, Río Muni 290) and it highlights the importance of the flow of species across the territories of the Gulf of Guinea. This idea is supported by the low number of endemic species observed in these territories.
Although the botanical exploratory level of Río Muni is relatively high when compared to the Central African countries, the number of species recorded so far is still far from the observed in neighboring Cameroon or Gabon, with 6,883 and 5,236 species respectively (Sosef & al. 2017Sosef M.S., Dauby G., Blach-Overgaard A., van der Burgt X., Catarino L., Damen T., Deblauwe V., Dessein S., Dransfield J., Droissart V., Duarte M.C., Engledow H., Fadeur G., Figueira R., Gereau R.E., Hardy O.J., Harris D.J., de Heij J., Janssens S., Klomberg Y., Klomberg Y., Ley A.C., Mackinder B.A., Meerts P., de Poel J.L. van, Sonke B., Stevart T., Stoffelen P., Svenning J.C., Sepulchre P., Zaiss R., Wieringa J.J. & Couvreur T.L. 2017. Exploring the floristic diversity of tropical Africa. BMC biology 15: 15.). Besides the differences in area among the three of them, these figures are pointing out the need of continuing with the collection effort in Río Muni. The number of species in the continental region and the entire Equatorial Guinea would likely increase if plant collecting efforts were extended to the poorly explored areas in the near future.
Threatened status and endemicity
⌅The number of threatened taxa (VU, EN and CR) is 144 (5.31% of the total taxa) of which 48 are under extinction risk, i.e., considered Endangered or Critically Endangered (Table 3). Two endemic species, Polyscias aequatoguineensis and Scleria mongomoensis are categorized as Endangered and should be regarded as prioritary species for Conservation plans and strategies. Nonetheless, a revaluation of the real situation of these species should be even more important to do since preliminary data indicate that the real threatened status of Vascular Plants in Equatorial Guinea is far from well known. As an example, we focus our discussion below on endemic or subendemic plants from Río Muni.
| NE-DD | LC | NT | VU | EN | CR | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Nº | % | Nº | % | Nº | % | Nº | % | Nº | % | Nº | % | |
| Pteridophyta | 132 | 92.96 | 9 | 6.34 | 0 | 0 | 1 | 0.7 | 0 | 0 | 0 | 0 |
| Gymnospermae | 1 | 50 | 0 | 0 | 1 | 50 | 0 | 0 | 0 | 0 | 0 | 0 |
| Magnoliods | 42 | 43.75 | 43 | 44.79 | 3 | 3.12 | 6 | 6.25 | 1 | 1.04 | 1 | 1.04 |
| Monocots | 389 | 65.79 | 177 | 31.21 | 1 | 0.17 | 8 | 1.41 | 11 | 1.94 | 1 | 0.17 |
| Eudicots | 1,082 | 57.55 | 652 | 34.68 | 31 | 1.65 | 81 | 4.3 | 30 | 1.6 | 4 | 0.21 |
| Total | 1,646 | 881 | 36 | 96 | 42 | 6 | ||||||
Of all threatened taxa, only three are non-native to Río Muni namely Terminalia neotaliala, Gossypium hirsutum (both naturalized) and Memecylon erythranthum (introduced); and only 11 species could be considered as strictly endemic to Río Muni (Table 4). This low number of endemic taxa is reflecting the absence of natural barriers in the territory.
| Family | Species | IUCN category | Preliminary assessment |
|---|---|---|---|
| Araliaceae | Polyscias aequatoguineensis Lejoly & Lisowski | EN (2021) | - |
| Aspleniaceae | Asplenium carvalhoanum Herrero, Aedo, Velayos & Viane | NE | CR (here) |
| Begoniaceae | Begonia aequatoguineensis Sosef & Nguema | NE | VU D2 (here) |
| Begoniaceae | Begonia monte-alenensis Sosef | NE | VU D2 (Sosef 2014Sosef M. 2014. Novitates Gabonenses 86. The Begonia clypeifolia complex (Begoniaceae) unravelled. Plant Ecology and Evolution 147(2): 224-236) |
| Cyperaceae | Scleria mongomoensis Bauters | EN (2020) | - |
| Euphorbiaceae | Grossera angustifolia Barberá & Riina | EN (2022) | - |
| Malvaceae | Scaphopetalum obiangianum M.E. Leal | NE | VU D2 (here) |
| Melastomataceae | Guyonia obamae (Lejoly & Lisowski) Veranso-Libalah & R. D. Stone (=G. arenaria (Jacq.-Fél.) Verano-Libalah & R.D. Stone | NE | NT (Lachenaud & al. 2018Lachenaud O., Stévart T., Boupoya A., Texier N., Dauby G. & Bidault E. 2018. Novitates Gabunensis 88: additions to the flora of Gabon and new records of little-known species. Plant Ecology and Evolution 151: 393-422.) |
| Melastomataceae | Nothodissotis alenensis Veranso-Libalah & O. Lachenaud | NE | VU D2 (Veranso-Libalah & al. 2019Veranso-Libalah M.C., Lachenaud O., Stone R.G. & Kadereit G. 2019. Nothodissotis (Melastomataceae), a new genus from Atlantic Central Africa, including the new species N. alenensis from Equatorial Guinea. PhytoKeys 118: 89-103. ) |
| Orchidaceae | Polystachya riomuniensis Stévart & Nguema | NE | LC/EN |
| Orchidaceae | Rhipidoglossum montealenense Descourvières, Stévart & P.J. Cribb | - | EN (Descourvières & al. 2013) |
| Orchidaceae | Vanilla chalotii Finet | NE | VU/EN |
| Podostemaceae | Macropodiella uoroensis Rial | NE | CR (here) |
From the 13 endemic/subendemic species, three of them (Scleria mongomoensis, Polyscias aequatoguineensis, and Grossera angustifolia) have been recently evaluated by the IUCN as EN (Larridon & Bauters 2020Larridon I. & Bauters K. 2020. Scleria mongomoensis. The IUCN Red List of Threatened Species 2020: e.T172032833A172033445. ; Paradis & al. 2021Paradis A.H., Ikabanga D.U., Bidault E., Texier N. & Stévart T. 2021. Polyscias aequatoguineensis. The IUCN Red List of Threatened Species 2021: e.T173360456A174512880. ; Ruiz de Diego & al. 2022Ruiz de Diego P., Riina R. & Barberá P. 2022. Grossera angustifolia. The IUCN Red List of Threatened Species 2022: e.T176584058A176601312.). Guyonia obamae records from Río Muni have been identified as G. arenaria, and the species was preliminary assessed as NT (Lachenaud & al. 2018Lachenaud O., Stévart T., Boupoya A., Texier N., Dauby G. & Bidault E. 2018. Novitates Gabunensis 88: additions to the flora of Gabon and new records of little-known species. Plant Ecology and Evolution 151: 393-422.), nonetheless its taxonomic situation is still unclear.
We confirm that 12 out 13 of the endemic species evaluated should be considered as threatened (Table 4). Only for the subendemic Polystachya riomuniensis, since the distribution range of the species is quite large, the Extent of Occurrence (EOO) criteria states it as Least Concern while the Area of Occupancy (AOO) indicates the taxon as EN. We consider a more realistic conservative approach until taxonomic studies confirm the identity of these 12 species or new collecting campaigns confirm the presence of these taxa beyond the current distribution ranges.
Preliminary assessments of NE taxa
⌅Scaphopetalum obiangianum is a shrub 20-150 cm tall, known from the understory of rain forest, at around 700 m in elevation (Leal 2007Leal M.E. 2007. Novitates Rio Munis 1. A new endemic Scaphopetalum (Malvaceae) from Mount Mitra, Equatorial Guinea. Blumea Journal of Plant Taxonomy and Plant Geography 52: 137-138. ). The species is endemic to Equatorial Guinea and is only known from one collection made by Leal in 2005 in Monte Mitra, which thus represents a single occurrence in the Litoral Province. The AOO is estimated as 4 km2, below the upper threshold for Critically Endangered status under subcriterion B2. The EOO is the same as the AOO. This occurrence therefore represents the entire known population of the species. It is located within a protected area (Monte Alen National Park), and no specific threats have been identified at the present time. Therefore, Scaphopetalum obiangianum is assigned a preliminary status of VU D2.
Begonia aequatoguineensis is an herb up to c. 5 cm high, known from primary forest at c. 450 m altitude (Sosef & Nguema Miyono 2010Sosef M.S.M. & Nguema Miyono N.S. 2010. New species of Begonia section Loasibegonia (Begoniaceae) from the Monte Alen region, Equatorial Guinea. Blumea Journal of Plant Taxonomy and Plant Geography 55: 91-93.). The species is endemic to Equatorial Guinea and is only known from one collection, which thus represents a single occurrence, made by Nguema Miyono at West of Mendung, in the Centro Sur Province. The AOO is estimated as 4 km2, below the upper threshold for Critically Endangered status under subcriterion B2. The EOO is the same as the AOO. This occurrence therefore represents the entire known population of the species. It is located within the protected area Monte Alén National Park and no specific threats have been identified at the present time. Therefore, Begonia aequatoguineensis is assigned a preliminary status of VU D2.
Asplenium carvalhoanum is an epiphyte, known from primary rainforest, endemic to Equatorial Guinea (Herrero & al. 2001Herrero A., Aedo C., Velayos M. & Viane R.L. 2001. A new species of Asplenium (Aspleniaceae, Pteridophyta) from Equatorial Guinea. Annales Botanici Fennici 38: 175-180.). The species is only known from one collection, made by Carvalho in Cogo, between Emangós and Ncó villages, in the Litoral Province, which thus represents a single occurrence. The AOO is estimated as 4 km2, below the upper threshold for Critically Endangered status under subcriterion B2. The EOO is the same as the AOO. This occurrence therefore represents the entire known population of the species. It is not located within a protected area and is threatened by logging and by small-scale harvesting. The most serious plausible threat is the logging. We infer a future decline in the extent and quality of its habitat, therefore Asplenium carvalhoanum is thus assessed as CR B2ab(iii).
Macropodiella uoroensis is endemic to Equatorial Guinea, known from the rapids of the Uoro river, at Centro Sur province. The species is only known from one collection made by Rial & Laso in 1994, representing a single occurrence. The AOO is estimated as 4 km2, below the upper threshold for Critically Endangered status under subcriterion B2. The EOO is the same as the AOO. This occurrence therefore represents the entire known population of the species. It is not located within a protected area and is potentially threatened by water pollution due to increase in urbanization. We infer a future decline in the extent and quality of its habitat hence, Macropodiella uoroensis is assessed as CR B2ab(iii).
Priority conservation areas
⌅The geographical analyses of threatened species from Río Muni revealed the value of the National System of Protected Areas of Equatorial Guinea (Fig. 3). A total of 618 records out of the 23,517 compiled correspond to threatened species (CR, EN or VU), 224 of them are outside protected areas, which means that 36.25% of the threatened plants of Río Muni do not have any protection at all. If we consider those Near Threatened taxa, there are 721 total occurrences, 276 outside protected areas (38.28%). Monte Alén National Park is by far the most important Protected Area in Río Muni, hosting 49.23% of the occurrences of threatened species in this continental region. Two protected areas, Río Campo, and Montes Temelón do not include any occurrence from threatened species (Fig. 3).
Endemicity and areas for conservation
⌅The conservation relevance of the system of protected areas of Equatorial Guinea comes to the fore when we consider the endemicity of the flora. Figure 4 shows the spatial distribution of the 13 endemic and subendemic species. Twenty-one of these occurrence records (46.6%) are included in protected areas. In this sense, the situation of Scleria mongomoensis, Macropodiella uoroensis, Polyscias aequatoguineensis, Grossera angustifolia and Asplenium carvalhoanum is particularly delicate since none of their localities has any protection status. As aforementioned, all of them, but Polyscias aequatoguineensis, could be also threatened under the IUCN category of Critically Endangered.
Expanding the area of the Monte Alén National Park and establishing a monitoring program for these species to establish corridors between protected areas or new areas of special interest for the flora are necessary strategies to achieve a sustainable management of plant diversity in Equatorial Guinea. Connecting the different protected areas or increasing the surface area of some of them seems to be the best alternative to include the greatest number of threatened species present in this region. Finally, we emphasize that coastal meadows are especially under protected from human impacts.