Diversity of Orchids from Continental Sub-Saharan Africa

Abstract

Africa is a vast continent containing many types of ecological environments. It harbors the second largest forest reserve in the world but its flora is not well known for lack of financial means to carry out botanical prospecting studies. While many families have been well studied, others like the Orchidaceae are little known. This study is intended to contribute to the knowledge of this family through its use and distribution in continental sub-Saharan Africa.

The overall analysis of the orchid flora was done based on the four major regions except North Africa and South Africa (West Africa, Central Africa, Southern Africa, and East Africa). This study is based on the investigation of the literature. We have consulted previous published studies on orchids, floras, and distribution maps of the targeted areas. We were able to draw up a list of 1373 species belonging to 88 genera. The results show that of the four phytogeographic zones, Central Africa is the richest with 708 species, followed by Southern Africa and East Africa with 637 and 583 species, respectively. West Africa, with 413 species, is the least rich area. Several uses have been listed. Mostly, orchids are using in pharmacopoeia, in feeding and as ornamental plants. We were also able to establish endemism in several countries (e.g., Tanzania, Zimbabwe, the Democratic Republic of Congo, Ethiopia, Cameroon, Mozambique, Zambia, Malawi, Rwanda, Angola, Kenya, Nigeria, Gabon, Central African Republic, Uganda, and Burundi).

1 Introduction

Third largest continent in the world in terms of area after Asia and America, African continent has a great diversity of ecological environments ranging from wet evergreen forests to vast desert areas [1]. With this multitude of vegetation, the African continent is rich in more than 62,000 species of flowering plants but still remains largely unknown. Compared to other continents, the diversity is relatively low. Some studies estimate this diversity probably at 25% of the world’s species. Several reasons could explain this ignorance. The fragmentation of Africa due to the history of colonization is believed to have encouraged sectarianism. The large surface area of the continent and the lack of financial support to carry out botanical inventories is also a cause of the ignorance of the flora of the African continent. Most of the country or regional floras of Africa are old.

African continents contain the second largest forest reserve in the world. While many botanical families have been well studied, others are very little known. This is the case of Orchidaceae family which has an estimated global richness of 25,000 species [2]. This family has good representation in tropical and equatorial regions of the world but in Africa it is little studied. The richness of the genera of the Orchidaceae is estimated at 700 accord [3]. This family presents the greatest diversity and number of species in flowering plants [4]. In Africa, the richness of Orchidaceae is estimated at 1500 species belonging to l 87 genera [5, 6].

The Orchidaceae family is important both in botanical terms for its richness, and economically through the use of several species as ornamental plants [7]. Many of these species are sold internationally as an ornamental. This international trade of the orchids species has an impact on the abundance of the species, in their habitats. Some species became rare, and others are on the way of extinction, while others have already disappeared. The main reason for their disappearance is the degradation of their habitat by human activities. Therefore, orchids represent an excellent indicator of the quality of biotopes in which they are found [8]. This work, which aims to contribute to the knowledge of the floristic diversity of the Orchidaceae family, will focus on species from sub-Saharan Africa, except South Africa.

2 Method of Data Collection

This work on the orchids of sub-Saharan Africa was based on the use of literature and on all the flora that we had at our disposal. We have particularly used the books presenting the distribution of Orchidaceae in the countries of sub-Saharan Africa [9, 10]. It should be noted that the work of these authors is based on specimens deposited in different herbaria around the world. We analyzed the flora of orchids according to the four major regions except North Africa and South Africa. Thus the areas considered in this work are: West Africa, Central Africa, Southern Africa (not the country), and East Africa.

3 Brief Presentation of Orchidaceae

3.1 Distribution of Orchids

The Orchidaceae are a cosmopolitan family with a very large ecological environment. Orchids are much more present in warm regions [11]. Herbaceous and perennial, the species of this family have colonized practically all habitats. They can be found in the coastal areas as well as at higher altitudes. However, they are absent from extreme environments such as Antarctica, the sea, the most arid deserts, and the coldest mountain peaks. Orchidaceae are more common in tropical areas where its flora represent nearly 10% of tropical flora. According to Ref. [11], they can be terrestrial plants (tropical, temperate, and boreal environments for geophytes with tubers or rhizomes), epiphytes (generally in tropical environments), and even lianas as species of Vanilla genera. In Africa, the Orchidaceae constitute an important part of the epiphytes of tropical forests. Among the 153 species of epiphytes recorded in the evergreen forests of West Africa, 101 belong to the Orchidaceae family [12].

3.2 Botanical Description and Systematic

The plants belonging to the Orchidaceae family are terrestrial or epiphytic herbs, rarely helophytes, never halophytes, aquatic, or parasitic. The terrestrial Orchidaceae are provided with important underground apparatus, in the form of tubers of stem or root origin or of rhizomes, on which are born the adventitious roots and the leafy and flowering aerial stems. The stems of Orchidaceae are simple or branched and erect. The creeping form is rarely observed.

The strongly adherent roots of orchids allow a good attachment to trees and better withstand the stresses of aerial life. In some species, the leafless vegetative apparatus is reduced to a system of green roots, from which the inflorescences arise directly.

In Orchidaceae family, the leaves are simple, alternate, more or less fleshy, with a sheathing base, parallel to the veins. They are often arranged in two rows, rarely opposite or in whorls. They are sessile or petiolate and sometimes reduced to scales. The greatest diversity at the leaf level is observed in terrestrial Orchidaceae, hence their extensive use as decorative plants.

Epiphytic Orchidaceae have both leathery and succulent, green, or spotted leaves with usually long, hanging aerial roots, gray or white, covered with a velamen, with a meristematic apex. This system absorbs the moisture and nutrients necessary for the life of the plant. These thick ligulate leaves reduce water loss and promote photosynthesis. The survival of many epiphytes in environments subject to extreme conditions is due to the development of particularly active photosynthetic tissues in all organs (stems, roots, and even flowers).

Many tropical and subtropical orchids, both terrestrial and epiphytic, have pseudo-bulbs as reserve organs for water and nutrients. Those pseudo-bulbs vary, depending on the species. We can observe from barely swollen stems to very hard, to apple-shaped bright green organs, from which the leaves emerge. A plant may have only one pseudo-bulb, but these may also be gathered in a tight group, or, in some tropical species, be spaced along a creeping or climbing rhizome. Their size varies from that of a pinhead to a thick cylinder up to 3 m high. Pseudo-bulbs are always on the ground or above ground level, but in several groups of terrestrial orchids in temperate regions, there are similar organs growing on roots in the ground.

The Orchidaceae family is constituted by five subfamilies which are the Epidendroideae, the Apostasioideae, the Vanilloideae, the Cypripedioideae, and the Orchidoideae [13]. The classification of African orchids has been a real challenge for a very long time [14]. Taxonomic confusions are not limited only to the specific level but also to the generic level. For example, the generic delineation within the African Angraecoid group resulted in the discovery of 6 new species and 2 new genera [14]. In addition, 30 species were not correctly assigned, from a phylogenetic point of view, to genera.

The taxonomic insufficiencies of this family, in continental Africa, are justified by several reasons including the political instability of the countries (making field missions difficult), logistical problems, the lack of effective protocols for inventories, etc. At the phylogenetic level, the studies showed that the genera Angraecopsis, Diaphananthe, and Margelliantha are polyphyletic while the genera Aerangis, Ancistrorhynchus, Bolusiella, Campylocentrum, Cyrtorchis, Dendrophylax, Eurychone, Microcoelia, Nephrangis, Podangis, and Solenangis are monophyletic [14].

4 The Orchids of Sub-Saharan Africa

4.1 Richness According to Geographic Areas

The Orchidaceae species inventoried in sub-Saharan Africa are 1373 species grouped into 88 genera. The genera Habenaria (391 spp.), Polystachya (279 spp.), Eulophia (232 spp.), and Bulbophyllum (115 spp.) are the important genera. These genera are followed by Disa, Satyrium, Tridactyle, Angraecum, Disperis, Rhipidoglossum, and Brachycorythis with more than 50 species. We recorded 108 species common to the 4 major regions (West Africa, Central Africa, East Africa, and Southern Africa). According to the work of Refs. [9, 10], the richness of Central Africa phytogeographic zones is 708 species. This zone is followed by southern Africa and eastern Africa with 637 and 583 species, respectively. These numbers are higher than those given by the work of Ref. [15]. For this author, East Africa is the richest region with 679 species followed by Central Africa with 517 species, South Africa with 425 species, and West Africa with 413 species. The region with the lowest orchid abundance is West Africa. Central Africa appears to be the most studied area. Indeed, several works have been carried out in this area by numerous researchers. After Central Africa, the orchids of East and South Africa which have been the best studied. In West Africa very few studies have been focused on Orchidaceae. However, in this area, the important work on the orchids of Côte d’Ivoire should be highlighted [4].

The most abundant species distributed in most countries are: Ansellia africana Lindl., Bolusiella alinae Szlach., Brachycorythis ovata Lindl., Brachycorythis pubescens Harv., Brachycorythis tenuior Rchb.f., Bulbophyllum fuscum Lindl., Bulbophyllum maximum (Lindl.) Rchb.f., Bulbophyllum scaberulum (Rolfe) Bolus, Cyrtorchis arcuata (Lindl.) Schltr. (Fig. 10), Eulophia angolensis (Rchb.f.) Summerh., Eulophia cucullata (Afzel. ex Sw.) Steud., Eulophia guineensis Lindl., Eulophia horsfallii (Bateman) Summerh., Habenaria ichneumonea (Sw.) Lindl., Habenaria schimperiana Hochst. ex A. Rich., Habenaria zambesina Rchb.f., Liparis nervosa (Thunb.) Lindl., Nervilia bicarinata (Blume) Schltr., Nervilia kotschyi (Rchb.f.) Schltr., Nervilia petraea (Afzel. ex Sw.) Summerh., Platylepis glandulosa (Lindl.) Rchb.f., Polystachya golungensis Rchb.f., Polystachya modesta Rchb.f., Polystachya concreta (Jacq.) Garay & H. R. Sweet., Rangaeris muscicola (Rchb.f.) Summerh., Rhipidoglossum rutilum (Rchb.f.) Schltr., Tridactyle anthomaniaca (Rchb.f.) Summerh., Tridactyle bicaudata (Lindl.) Schltr., Tridactyle filifolia (Schltr.) Schltr. et Tridactyle tridactylites (Rolfe) Schltr.

4.2 Endemism of Orchidaceae Species in the Sub-Saharan Countries

Apart from species widely distributed in all regions, other species seem rather confined to a given country or region. Recent studies showed that 284 species are found in East Africa, 259 species in Central Africa, 201 in South Africa, and only 58 species in South Africa [9, 10]. There is thus an endemism in certain countries or in two border countries.

The richness countries in endemic species based on the distribution map of herbarium samples are Tanzania (78 species), Zimbabwe (41 species), the Democratic Republic of Congo (38 species), Ethiopia (32 species), Cameroon (29 species), Mozambique (27 species), Zambia (24 species), Malawi (23 species), Rwanda (21 species), Angola (20 species), Kenya (18 species), Nigeria (17 species), Gabon (16 species), Central African Republic (8 species), and Uganda and Burundi with 5 species each [9, 10]. This number of endemic species could vary with taxonomic revisions and sampling effort conducted in several countries. The endemic species found in Tanzania include: Aerangis confusa J. Stewart, Ancistrorhynchus parviflorus Summerh., Angraecopsis tenerrima Kraenzl.; I. & E. la Croix, Angraecum brevicornu Summerh., Bonatea volkensiana (Kraenzl.) Rolfe, Brachycorythis tanganyikensis Summerh, Cynorkis pleistadenia (Rchb.f.) Schltr., Disperis elaphoceras Verdc., Epipactis ulugurica Mansf., Eulophia amblyosepala (Schltr.) Butzin, Habenaria apiculata Summerh., Holothrix hydra P. J. Cribb, Margelliantha clavata P. J. Cribb, Mystacidium nguruense P. J. Cribb, Nervilia similis Schltr, Oeceoclades zanzibarica (Summerh.) Garay & P. Taylor, Platycoryne ambigua (Kraenzl.) Summerh., Polystachya acuminata Summerh., Pterygodium ukingense Schltr, Rangaeris schliebenii (Mansf.) P. J. Cribb, Rhipidoglossum melianthum (P. J. Cribb) Senghas, Satyrium comptum Summerh., Tridactyle brevifolia Mansf., Vanilla zanzibarica Rolfe, Zeuxine lunulata P. J. Cribb & J. Bowden.

Kenya, which borders Tanzania, has 243 Orchidaceae species divided into 47 genera according to Ref. [16]. Among the species we note as endemic to Kenyan flora are Ancistrorhynchus paysanii Senghas, Angraecum decipiens Summerh., A. spectabile Summerh., Bilabrella kraenzliniana, Polystachya bella Summerh., Eulophia endlichiana (Kraenzl)., Habenaria altior Rendle, H. bonateoides Ponsie, H. haareri Summerh., H. keniensis Summerh., H. thomsonii Rchb. f., Holothrix pentadactyla (Summerh.) Summerh., Polystachya holstii Kraenzl., P. teitensis P. J. Cribb, Rhipidoglossum montanum (Piers) Senghas, Ypsilopus longifolius (Kraenzl.) Summerh, Y. viridiflorus P. J. Cribb & J. Stewart.

According to the distribution map, these two East African countries have in common 17 endemic species found only on their territory. These are: Aerangis coriacea Summerh., Angraecopsis breviloba Summerh, Angraecum viride Kraenzl., Bonatea rabaiensis (Rendle) Rolfe, Cynorkis uncata (Rolfe) Kraenzl., C. usambarae Rolfe, Disperis egregia Summerh., Habenaria helicoplectrum Summerh., H. plectromaniaca Rchb.f. & S. Moore, Polystachya confusa Rolfe, P. disiformis J. Cribb, P. leucosepala P. J. Cribb, P. shega Kraenzl., Tridactyle cruciformis Summerh., T. furcistipes Summerh., T. tanneri P. J. Cribb, Rhipidoglossum tanneri (P. J. Cribb) Senghas.

Ethiopia has 160 Orchidaceae species, divided into 37 genera [15]. These authors have recorded 26 endemic species while 35 species have been reported by Refs. [9, 10]. Among the species indicated, we can cite Angraecopsis trifurca (Rchb.f.) Schltr, Habenaria lefebureana (A. Rich.) T. Durand & Schinz, Disa pulchella Hochst. ex A. Rich., Disperis crassicaulis Rchb.f., Eulophia abyssinica Rchb. f., Habenaria aethiopica S. Thomas & P. J. Cribb, Holothrix praecox Rchb.f., Liparis abyssinica A. Rich., Polystachya aethiopica P. J. Cribb, Rhipidoglossum candidum (P. J. Cribb) Senghas, Roeperocharis alcicornis Kraenzl., Satyrium aethiopicum Summerh.

In Central Africa, Cameroon harbors the highest number of endemic species with 29 endemic species recorded [9, 10]. In a previous work in this country, 44 endemic species were identified [17]. These endemic species are, among others, Ancistrorhynchus constrictus Szlach. & Olsz., Angraecopsis cryptantha Cribb, Angraecum curvipes Schltr., Bolusiella zenkeri (Kraenzl.) Schltr., Bulbophyllum saltatorium Lindl., Chamaeangis letouzeyi Szlach. & Olsz., Cheirostylis divina (Guinea) Summerh. var. ochyrae Szlach. & Olsz., Diaphananthe garayana Szlach. & Olsz., Disperis kamerunensis Schltr., Disperis nitida Summerh., Gastrodia africana Kraenzl., Genyorchis macrantha Summerh., Habenaria alinae Szlach., Liparis kamerunensis Schltr., Microcoelia sanfordii L. Jónss., Ossiculum aurantiacum P. J. Cribb & Laan, Platycoryne alinae Szlach., Polystachya albescens Ridl. subsp. angustifolia (Summerh.) Summerh., Rangaeris trachypus (Kraenzl.) Guillaumin, Rhipidoglossum ochyrae Szlach. & Olsz., Rhipidoglossum polydactylum (Kraenzl.) Garay, Vanilla ochyrae Szlach. & Olsz.

Orchids species of Gabon can be checked at http://orchideesgabon.e-monsite.com/pages/orchidees-liste.html. This site gives a non-exhaustive list of 284 species divided into 53 genera among which 16 endemic species [9, 10]. These endemics species are: Angraecopsis hallei Szlach. & Olszewski, Angraecum cribbianum Szlach. & Olszewski, Bulbophyllum apodum Hook.f., B. subligaculiferum J. J. Vern., Cyrtorchis henriquesiana (Ridl.) Schltr., Dinklageella villiersii Szlach. & Olszewski, Rhipidoglossum magnicalcar Szlach. & Olszewski, Taeniorrhiza gabonensis Summerh., Tridactyle latifolia Summerh., T. minutifolia Stévart & D’Haijère, T. pentalobata P. J. Cribb & Stévart, Vanilla acuminata Rolfe, V. chalotii Finet, V. hallei Szlach. & Olszewski, Veyretella hetaerioides (Summerh.) Szlach. & Olszewski, V. flabellata Szlach.

Gabon and Cameroon have 11 species in common [17]. These species are: Aerangis gracillima (Kraenzl.) J. C. Arends & J. Stewart, Ancistrorhynchus obovata Stévart inédit., Angraecum eichlerianum Kraenzl. var. curvicalcaratum Szlach. & Olsz., Bulbophyllum fayi J. J. Verm., Bulbophyllum minutifolium Stévart in Stévart & al., Diaphananthe ceriflora J. B. Petersen, Eggelingia gabonensis P. J. Cribb & Laan, Genyorchis platybulbon Schltr., Halleorchis aspidogynoides Szlach. & Olsz., Polystachya kubalae Szlach. & Olsz., Polystachya letouzeyana Szlach. & Olsz. However, 19 species have been indicated as common endemic species to these two countries [9, 10].

Cameroon shares with the Republic of Congo, the Democratic Republic of Congo, Equatorial Guinea, and Ethiopia five endemic species which are Habenaria phantasma la Croix, Habenaria stenoceras Summerh., Rhipidoglossum monte-alenense Descourvières, Stévart & P. J. Cribb and Stolzia grandiflora P. J. Cribb. Habenaria egregia Summerh. is only observed in Cameroon, Ethiopia, and Kenya.

The species Orestias micrantha Summerh., Polystachya batkoi Szlach. & Olszewski, Polystachya letouzeyana Szlach. & Olszewski, Polystachya moniquetiana Stévart & Geerinck, Polystachya riomuniensis Stévart & Nguema and Polystachya stodolnyi Szlach. & Olszewski are only found in Cameroon, Gabon, and Equatorial Guinea. Cameroon also shares with Gabon and the Republic of Congo the species Habenaria lisowskii Szlach. and with Gabon and the Democratic Republic of Congo the species Tridactyle laurentii (De Wild.) Schltr. Two species Polystachya bifida Lindl. and Polystachya testuana Summerh are endemic to Gabon and Equatorial Guinea.

The Democratic Republic of Congo has 38 endemic species according to the distribution maps of Refs. [9, 10]. Some of these species are: Angraecum mofakoko De Wild., Bulbophyllum horridulum J. J. Vern., Cynorkis summerhayesiana Geerinck, Diaphananthe divitiflora (Kraenzl.) Schltr., Disa alinae Szlach., Eulophia fernandeziana Geerinck, Habenaria garayana Szlach. & Olszewski, Polystachya alicjae Mytnik, Roeperocharis maleveziana Geerinck, Tridactyle fimbriatipetala (De Wild.) Schltr., Tridactyle stipulata (De Wild.) Schltr., Tridactyle vanderlaaniana Geerinck.

In République Centrafricaine, we found only eight endemics species which are: Ancistrorhynchus brevifolius Finet, Eulophia falcatiloba Szlach. & Olszewski, Habenaria kornasiorum Szlach. & Olszewski, Habenaria letestuana Szlach. & Olszewski, Microcoelia jonssonii Szlach. & Olszewski, Platycoryne lisowskiana Szlach. & Kras, Platycoryne ochyrana Szlach., Disperis raiilabris Summerh.

A total of 21 endemic species from Rwanda flora has been noticed [9, 10]. They are: Bulbophyllum kivuense J. J. Vern., Diaphananthe eggelingii P. J. Cribb, Diaphananthe liae Ed. Fischer, Killmann, J.-P. Lebel & Delep., Disperis natascha-oppeltae Eb. Fischer, Killmann, Disperis reklieberae Eb. Fischer, Eulophia pocsii Eb. Fisch., Gastrodia rwandensis Eb. Fisch. & Killmann, Habenaria bequaertii Summerh., Margelliantha lebelii Eb. Fischer & Killmann, Polystachya anastacialynae Eb. Fischer, Polystachya bruechertiae Eb. Fischer, Killmann & J.-P. Lebel, Polystachya erica-lanzae Eb. Fischer, Polystachya isabelae Mytnik, Polystachya lawalreeana Geerinck, Polystachya samilae Eb Fisch., Rhipidoglossum cuneatum (Summerh.) Garay, Rhipidoglossum mildbraedii (Kraenzl.) Garay, Stolzia heiligenthalii Eb. Fisch., Killmann, Stolzia kalkhof-roseae Eb. Fischer, Killmann, Tridactyle nanne-ritzkae Eb. Fischer, Killmann, Lebel & Delepierre, Tridactyle stevartiana Geerinck.

According to the two authors [9, 10], there are five endemic species in Burundi which are: Habenaria lewallei Geerinck, Polystachya editae Eb. Fisch., Polystachya lacroixiana Geerinck, Polystachya maculata P. J. Cribb, Polystachya walravensiana Geerinck & Arbonn.

Burundi and Rwanda share 16 endemic species which are: Habenaria coeloglossoides Summerh., Habenaria lehae Eb. Fischer, Polystachya tridentata Summerh, Polystachya troupiniana Geerinck, Polystachya undulata P. J. Cribb & Podz., Polystachya woosnamii Rendle, Rhaesteria eggelingii Summerh., Polystachya proterantha P. J. Cribb, Habenaria brachylobos (Summerh.) Summerh., Rhipidoglossum ovale (Summerh.) Garay, Tridactyle eggelingii Summerh., Margelliantha burttii (Summerh.) P. J. Cribb, Polystachya fabriana Geerinck, Polystachya macropoda Summerh., Rhipidoglossum arbonnieri (Geerinck) Eb. Fischer, Killmann, Rhipidoglossum delepierreanum (Lebel & Geerinck) Eb. Fisch., Killmann.

In West Africa, the orchids flora of Nigeria and Côte d’Ivoire is well known compared to the other countries of the area. Nigeria is rich with 239 species divided between 34 genera. It is the country with the most endemic species in West Africa [9, 10]. According to these authors, there are 15 endemic species. But other studies based on inventories reveal 7 endemic species which are: Diaphananthe dorotheae (Rendle) Summerh., Genyorchis apertiflora Summerh., Habenaria linguiformis Summerh., Habenaria nigerica Summerh., Habenaria phylacocheira Summerh., Habenaria prionocraspedon Summerh., Alectra virgata Hemsl., which are indicated to be endemic species of Nigeria [18].

By observing the distribution maps of species, Nigeria (West Africa), neighbor of Cameroon (Central Africa), shares with this country 26 endemic species [9, 10]. These are for example: Aerangis gravenreuthii (Kraenzl.) Schltr., Ancistrorhynchus serratus Summerh., Angraecopsis cryptantha P. J. Cribb, Angraecum angustum (Rolfe) Summerh., Diaphananthe lanceolata (Summerh.) P. J. Cribb & Carlsward, Disperis mildbraedii Schltr. ex Summerh., Genyorchis micropetala (Lindl.) Schltr, Habenaria alinae Szlach., Liparis letouzeyana Szlach. & Olszewski, Platycoryne megalorrhyncha Summerh., Polystachya alpina Lindl., Tridactyle lagosensis (Rolfe) Schltr., Rhipidoglossum obanense (Rendle) Summerh. Platylepis xerostele Ormerod is observed on the border of Nigeria and Cameroon.

The book entitled Les Orchidées de Côte d’Ivoire gave for this country a total of 264 species divided into 48 genera [4]. This study increased the number of species recorder in the frame of previous studies [19]. Indeed three new species (Ancistrorbyncbus akeassiae Perez-Vera, Bulbupbyllum danii Perez-Vera, and Cbamaeangis pauciflora Perez-Vera) and two new varieties (Bulbopbyllum scaberulum (Rolfe) Bolus var. album Perez-Vera and Cyrtorcbis broumii (Rolfe) Schltr. var. guillaumetii Perez-Vera) have been described [4].

Côte d’Ivoire shares with Liberia and Sierra Leone three species: Polystachya pseudodisa Kraenzl., Tridactyle fusifera Mansf., and Bulbophyllum denticulatum Rolfe. Polystachya leonensis Rchb.f. is found in Guinea and Sierra Leone. This species is not counted among ivorian orchids, although it is collected near the Ivorian border. This species has been also observed in Cameroon flora. The species Polystachya bancoensis Burg has only been observed in Côte d’Ivoire and Ghana. The species Polystachya rivae Schweinf. encountered in Ethiopia has been reported in Côte d’Ivoire [9, 10]. This species is not included in the list compiled by Ref. [4].

Côte d’Ivoire, Liberia, Sierra Leone, and Ghana share Bulbophyllum danii Perez-Vera, Angraecum modicum Summerh., Diaphananthe suborbicularis Summerh. and Bulbophyllum parvum Summerh. The species Malaxis melanotoessa Summerh. and Polystachya bequaertii Summerh. et Polystachya elastica Lindl. are only found in Liberia and Sierra Leone. Species like Habenaria jacobi Summerh. and Habenaria jaegeri Summerh. are found in Liberia and Sierra Leone and Guinea. The species Habenaria angustissima Summerh. is endemic in Senegal and Guinea. The species Bulbophyllum parvum Summerh. and Diaphananthe suborbicularis Summerh. are found in Ghana and Sierra Leone. The species Rhipidoglossum laticalcar (J. B. Hall) Senghas is only found in Ghana and Nigeria. Polystachya monolenis Summerh. is an endemic species of Sierra Leone and Ghana. The species Rhipidoglossum laxiflorum Summerh. has been reported in Ghana, Togo, and Côte d’Ivoire in the work of Refs. [9, 10]. However, this species has not been reported in Côte d’Ivoire [4]. Habenaria dinklagei Kraenzl. has only been observed in Liberia and Nigeria. It has not been found in other regions between the two countries.

The well-known Southern African countries for orchids are Angola, Malawi, Mozambique, Zambia, and Zimbabwe. The flora of Angola is rich of 228 orchids belonging to 40 genera [20]. This Angolan flora has 20 endemic species according to Refs. [9, 10]. For example we can mention Angraecopsis gassneri G. Will., Brachycorythis mixta Summerh., Diaphananthe welwitschii (Rchb.f.) Schltr., Eulophia aloifolia Welw. ex Rchb.f, Eulophia protearum Rchb.f., Habenaria decaptera Rchb.f., Habenaria robusta Welw. ex Rchb.f., Holothrix klimkoana Szlach. & Marg., Polystachya angularis Rchb.f., Satyrium aciculare van der Niet & P. J. Cribb et Satyrium welwitschii Rchb.f.

The site https://www.malawiflora.com/speciesdata/family.php?family_id=161 gave for Malawi 420 Orchidaceae species grouped into 57 genera. Among these 420 species, 23 are endemic according to the work of Refs. [9, 10]. Three hundred six species distributed among 48 genera have been counted by Ref. [21]. It is understandable that this number may be increasing with the work prior to this study [22]. In this flora of Malawi, 23 species are endemic according to the work of Refs. [9, 10]. Those species are: Aerangis carnea J. Stewart, Angraecopsis lovettii P. J. Cribb, Angraecum umbrosum P. J. Cribb, Bonatea stereophylla (Kraenzl.) Summerh., Disa walleri Rchb.f., Disperis decipiens Verdc.; Habenaria diselloides Schltr., Holothrix buchananii Schltr., Polystachya mzuzuensis P. J. Cribb & la Croix, Polystachya suaveolens P. J. Cribb, Rhipidoglossum oxycentron (P. J. Cribb) Senghas, Satyrium afromontanum la Croix & P. J. Cribb.

Mozambique harbors 232 species and 49 genera of orchids with 7 endemic species [23]. These species are: Cyrtorchis glaucifolia Summerh., Disperis mozambicensis Schltr., Eulophia biloba Schltr., Eulophia bisaccata Kraenzl., Habenaria hirsutissima Summerh., Habenaria mosambicensis Schltr. et Liparis hemipilioides Schltr. In addition, 14 other species are shared with Zimbabwe, Tanzania, Malawi, and South Africa. The country shares 10 endemic species with Zimbabwe: Bulbophyllum ballii P. J. Cribb, Cynorkis anisoloba Summerh., Disa chimanimaniensis (H. P. Linder) H. P. Linder, Disa zimbabweensis H. P. Linder, Neobolusia ciliata Summerh., Oligophyton drummondii H. P. Linder & G. Will., Polystachya subumbellata P. J. Cribb & Podz., Polystachya valentina la Croix & P. J. Cribb, Satyrium flavum la Croix, and Schizochilus lepidus Summerh. Mozambique shares, respectively, with Malawi and Tanzania the species Polystachya songaniensis G. Will. et Habenaria stylites Rchb.f. & S. Moore subsp. johnsonii (Rolfe) Summerh.

In Zambia 412 orchids species divided into 46 genera are recorded on the site https://www.zambiaflora.com/speciesdata/family.php?family_id=161. Among these species, 22 are endemic. These species are: Bonatea antennifera Rolfe, Bonatea cassidea Sond., Cynorkis clarae Geerinck, Disa helenae Buscal. & Schltr., Disa praecox (H. P. Linder) H. P. Linder in Linder & Kurzweil, Disperis bifida P. J. Cribb, Eulophia brenanii P. J. Cribb & la Croix, Eulophia richardsiae P. J. Cribb & la Croix; Habenaria argentea P. J. Cribb, Habenaria bertauxiana Szlach. & Olszewski, Habenaria binghamii G. Will., Habenaria macrotidion Summerh., Habenaria orthocentron P. J. Cribb, Habenaria pasmithii G. Will., Habenaria petraea Renz & Grosvenor, Habenaria tubifolia la Croix & P. J. Cribb, Habenaria velutina Summerh., Holothrix villosa Lindl. var. villosa, Polystachya asper P. J. Cribb & Podz., Polystachya erythrocephala Summerh., Polystachya mafingensis P. J. Cribb, Pteroglossaspis corymbosa G. Will.

Zimbabwe has 358 species of orchids for 54 genera that can be viewed at the site https://www.zimbabweflora.co.zw/speciesdata/family.php?family_id=161.

A list of the plant taxa endemic or nearly endemic to Zimbabwe has not previously been compiled [24]. The list of endemics identified in this flora will be based on Refs. [9, 10]. Zimbabwe comes after Tanzania with 41 endemic species. We have retained Aeranthes parkesii G. Will., Angraecum chimanimaniense G. Will., Bulbophyllum chikukwa Fibeck & Mavi, Brownleea galpinii Bolus subsp. galpinii, Cynorkis anisoloba Summerh., Disa chimanimaniensis (H. P. Linder) H. P. Linder, Disperis concinna Schltr., Eceoclades quadriloba (Schltr.) Garay & P. Taylor, Eulophia foliosa (Lindl.) Bolus, Goodyera afzelii Schltr, Habenaria bicolor Conrath & Kraenzl., Holothrix macowaniana Rchb. f., Mystacidium gracile Harv., Neobolusia ciliata Summerh., Oeceoclades pandurata (Rolfe) Garay & P. Taylor, Oligophyton drummondii H. P. Linder & G. Will., Platycoryne affinis Summerh., Polystachya pubescens (Lindl.) Rchb.f., Satyrium flavum la Croix, Schizochilus calcaratus P. J. Cribb & la Croix, Stenoglottis woodii Schltr., Tridactyle hurungweensis W. Fibeck.

5 Uses of Orchidaceae Species in African Countries

Orchids are best known for their beautiful flowers which make them a resource of great economic importance in the horticultural industry.

Very little information related to the indigenous African ornamental orchids are available. However, several orchids from other continents or countries have been introduced and domesticated and constitute important sources of income for African horticulturalists. Among these species Arachnis hookeriana (Rchb.f.) Rchb., Arachnis flos-aeris (L.) Rchb.f. native to Asia, Papilionanthe hookeriana (Rchb.f.) Schltr. native to Malaysia and Bletilla striata (Thunb.) Rchb.f. from Japan, China, and Tibet. These species are cultivated and sold in Cameroon [25]. Ansellia africana Lindl. (Fig. 1), nicknamed the panther orchid because of its remarkable size of flowers and its yellow color streaked with brown, is an ornamental species in Gabon. This species is also called the queen of African orchids. Its range stretches from West Africa to South Africa. This large epiphytic orchid is arguably the most popular African orchid in the West. In Gabon, we can also see, Eulophia bouliawongo (Rchb.f.) J.Raynal (Eulophia oedoplectron Summerh.), another ornamental orchid, named the queen of marshes and coastal savannas prone to flooding. It is a large pink orchid over 2 m tall. Its flower stalk can produce up to 35 quite spectacular, deep pink flowers (https://www.lepratiquedugabon.com/les-orchidees-du-gabon/).

Fig. 1

Image of Ansellia africana Lindl. (From Aké-Assi)

Some orchids are also consumed by several communities in Africa. The species of orchids consumed by people are different from one country to another. However, Disa robusta N.E.Br. (Fig. 2) and Satyrium buchananii Schltr. are eaten in several countries. In Cameroon (Central Africa), the underground organs of Habenaria keayi Summerh. and Habenaria zambesina Rchb.f. (Fig. 3) are eaten [26]. Orchids are also eaten in East Africa. In Malawi the tubers of several orchids are used for food. These are, among others, Disa engleriana Kraenzl. (Fig. 4), Disa zombica N.E.Br., Habenaria walleri Rchb.f., Satyrium amblyosaccos Schltr. [27]. In Tanzania these are Brachycorythis pleistophylla Rchb.f., Disa erubescens Rendle, Disa ochrostachya Rchb.f., Eulophia schweinfurthii Kraenzl., Habenaria xanthochlora Schltr., Satyrium atherstonei Rchb.f., Disa robusta N.E.Br., Satyrium robustum Schltr., Satyrium sceptrum Schltr., Satyrium acutirostrum Summerh., Roeperocharis wentzeliana Kraenzl. which are used for the preparation of several meals [28]. In Benin (West Africa), Eulophia horsfallii (Bateman) Summerh. (Fig. 5), Habenaria cirrhata (Lindl.) Rchb.f. (Fig. 6), and Nervilia bicarinata (Blume) Schltr. are used in the preparation of sauces [29].

Fig. 2

Image of Disa robusta N.E.Br.

Fig. 3

Image of Habenaria zambesina Rchb.f.

Fig. 4

Image of Disa engleriana Kraenzl.

Fig. 5

Image of Eulophia horsfallii (Bateman) Summerh.

Fig. 6

Image of Habenaria cirrhata (Lindl.) Rchb.f.

An often-overlooked value of plants in the Orchidaceae family is their role in medicine. In many countries of Europe, America, Asia, and Africa, orchids have been used as traditional medicine for a very long time. Particularly in Africa, they are used in human and animal medicine. In Benin, in human health, orchids are used to cure several diseases [29]. Calyptrochilum christyanum (Rchb.f.) Summerh. is used in the treatment of dysmenorrhea (painful periods), edema of the lower limbs, malaria, and liver disease (disease of the faith). This species is also used to speed up the walking of a baby. Eulophia guineensis Lindl. is known to cure edema of the lower extremities, cough, epigastralgia (stomach pain), and fever. Habenaria schimperiana Hochst. ex A. Rich. is used to cure visual disturbances. To treat fever, myalgia (muscle pain), urinary disorders, epigastralgia (stomach pain), people of Benin use Nervilia bicarinata (Blume) Schltr. Nervilia kotschyi (Rchb.f.) Schltr. is used to treat dysmenorrhea (painful periods), epigastralgia (stomach pain), and cough [29]. In Cameroon, orchids are also used to treat several diseases. Angraecum angustipetalum Rendle is used for bone fortification of children. It is also used to perform abortions. This species is also used against snakes. Ancistrorhynchus serratus Summerh. is used to treat diabetes. Bulbophyllum fuscum var. melinostachyum (Schltr.) J. J. Verm., Bulbophyllum barbigerum Lindl., Bulbophyllum intertextum Lindl., and Bulbophyllum calyptratum Kraenzl. are used to cure diseases such as side pain, otodynia (ear pain), burns, wounds, and dermatoses (skin diseases). Cyrtorchis arcuata (Lindl.) Schltr. (Fig. 7) is recommended in the treatment of diabetes and skin diseases.

Fig. 7

Image of Cyrtorchis arcuata (Lindl.) Schltr.

Diaphananthe bidens (Afzel. ex Sw.) Schltr. (Fig. 8) is used for fertility. Graphorkis lurida (Sw.) Kuntze is used to treat coughs and tuberculosis. Habenaria procera (Afzel. ex Sw.) Lindl. is recommended for the purification of blood, gastritis, and arthritis. Liparis nervosa (Thunb.) Lindl. is used to treat ulcers and burns. Listrostachys pertusa (Lindl.) Rchb.f. (Fig. 9) is recommended for epigastralgia (stomach pain), constipation, and measles. Polystachya concreta (Jacq.) Garay & H. R. Sweet, Polystachya cultriformis (Thouars) Lindl. ex Spreng., and Polystachya caloglossa Rchb.f. are used to treat rheumatism, arthritis, measles, and burns. Tridactyle tridactylites (Rolfe) Schltr. is used for the treatment of dementia or mental disorders [25].

Fig. 8

Image of Diaphananthe bidens (Afzel. ex Sw.) Schltr. (From CSRS)

Fig. 9

Image of Listrostachys pertusa. (From the Parc National des Île Ehotilés)

In Benin, orchids are used spiritually. Calyptrochilum christyanum (Rchb.f.) Summerh. is used to attract good luck, the power of prophecy. It also has a vanishing power. Eulophia guineensis Lindl. fights the spirits of twins. Nervilia bicarinata (Blume) Schltr. (Fig. 10) is used for the power of prophecy. This species is also used to fight against the spirit of the deceased, witchcraft, and the spirits of twins [29]. In Cameroon, Ansellia africana Lindl. is used to ward off evil spirits and promote romantic relationships. Angraecum birrimense Rolfe, Bulbophyllum lupulinum Lindl., and Bulbophyllum falcatum (Lindl.) Rchb.f. are used to fight witchcraft. These species are also used to make predictions. Calyptrochilum emarginatum (Afzel. ex Sw.) Schltr. is used for seduction and luck [25].

Fig. 10

Image of Nervilia bicarinata (Blume) Schltr. (From Sinfra)

In animal health, Calyptrochilum christyanum (Rchb.f.) Summerh. and Habenaria cirrhata (Lindl.) Rchb.f. are used to treat diseases in chickens [29].

6 Conclusion

Based on this review of the literature, the contribution of the sub-Saharan African orchid flora is estimated to be more than 5% of the world flora of orchids. It is clear that the number of species is underestimated taking into account the fact that several regions of the continent were not highly inventoried. Also, many species are epiphytes, thus difficult to be collected. Orchidaceae is a diverse family and important for communities for the diversity of its uses (ornamental, food, medicine, etc.). The fact that some regions are more studied than others should be highlighted. For instance, Central and East Africa are relatively well known compared to West Africa. With the high rate of deforestation in Africa, several species could be threatened in the continent. Intensive prospection of understudied areas should be carried out to avoid the loss of many species. Also, it is important to assess the conservation status of the African orchids.