Contribution to the ecological study of orchids in the Comoros archipelago: floristic diversity, biogeography, ecological status, and conservation challenges

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Greener Journal of Agricultural Sciences

ISSN: 2276-7770

Vol. 16(3), pp. 123-140, 2026

Copyright ©2026, Creative Commons Attribution 4.0 International.

https://gjournals.org/GJAS

DOI: https://doi.org/10.15580/gjas.2026.3.062426095

Description: C:\Users\user\Documents\GJOURNALS\GJAS Logo.jpg

Title in English

Contribution to the ecological study of orchids in the Comoros archipelago: floristic diversity, biogeography, ecological status, and conservation challenges

Title in French

Contribution à l’étude écologique des orchidées de l’archipel des Comores : diversité floristique, biogéographie, statut écologique et enjeux de conservation

Maoulida Mohamed ABDILLAHI1,2,4*; Frédéric BIORET2; Vincent BOULLET2; Étienne VENNETIER3

1. Laboratory of Geobotany and Phytosociology, INRAPE, National Research Institute for Agriculture, Fisheries and the Environment, P.O.Box 404, M’dé, Ex-CEFADER, Comoros

2. University of Brest, EA 7462 Geoarchitecture Territories, Urbanization, Biodiversity, Environment, Brest, France

3. Teacher, LPO Gustave Eiffel, Kahani, 97680 Ouangani, Mayotte

4. BP. 906. Specialization in Plant Biology and Ecology, Faculty of Sciences, University of Antananarivo

ARTICLE’S INFO

Article No.: 062426095

Type: Research

Full Text: PDF, PHP, HTML, EPUB, MP3

DOI: 10.15580/gjas.2026.3.062426095

Accepted: 03//07/2026

Published: 04/08/2026

 

*Corresponding Author

ABDILLAHI Maoulida Mohamedi

Laboratory of Geobotany and Phytosociology, INRAPE, National Research Institute for Agriculture, Fisheries and the Environment, P.O.Box 404, M’dé, Ex-CEFADER, Comoros

E-mail: abdillahimaoulida@yahoo.fr; abdillahifsrp@gmail.com

Keywords: Biogeography, conservation, IUCN status, orchids, Comoros Archipelago

Mots clés : Inventaire, biogéographie, Conservation, statut UICN, Orchidées, Archipel des Comores

       

ABSTRACT

  The Malagasy biogeographical region, which includes the Comoros archipelago, is known worldwide for its natural wealth and as a biodiversity hotspot. The degradation of natural ecosystems threatens certain specialized species, including orchids. The aim of this study was to determine the diversity, assess the biogeography, and evaluate the ecological status of orchid species in the Comoros archipelago based on literature reviews, supplemented by field surveys and the application of IUCN criteria (version 4.0). The results of this study identified 148 species, subspecies, and varieties distributed across 33 genera. The endemism rate is 47%, with 63% being native. Grande Comore is the island with the highest number of endemic species (7 strictly endemic species). This flora has a closer affinity with Madagascar (47%) than with other neighboring countries: (3%) with the African continent, (1%) with Asia, or (2%) with the Mascarene Islands. Fifteen species are critically endangered (CR) (8%), seven are endangered (EN) (5%), 27 are vulnerable (VU) (16%), nine are near threatened (NT) (6%), 27 are of least concern (LC) (18%), and 68 are data deficient (DD) (46%). As part of the implementation of a biodiversity conservation management policy, measures must be taken quickly by local authorities to ensure the conservation of these species, some of which are endangered.

In French

La région biogéographique malgache dont fait partie l’archipel des Comores est connue mondialement par sa richesse naturelle mais aussi comme un “ hotspot ” pour la conservation de la biodiversité. La dégradation des écosystèmes naturels met en danger certaines espèces spécialisées dont les orchidées. L’objet de cette étude est de déterminer la diversité, d’évaluer la biogéographie et le statut écologique des espèces d’orchidées de l’archipel des Comores sur la base d’inventaires bibliographiques, complétés par des inventaires de terrains et l’application des critères de l’UICN (version 4.0). Les résultats de cette étude ont permis d’inventorier 148 espèces, sous-espèces et variétés réparties dans 33 genres. Le taux d’endémisme est de 47% et avec 63% d’indigénat. La Grande Comore est l’île la plus riche en espèces endémiques (avec 7 espèces endémiques strictes) pour cette ile. Cette flore possède une affinité plus proche de Madagascar (47%) qu’avec les autres pays voisins : (3%) avec le continent Africain, (1%) avec l’Asie ou (2%) avec les Mascareignes. 15 espèces sont en danger critique (CR) (8%), 7 espèces en danger (EN) (5%), 27 espèces vulnérables (VU) (16%), 9 espèces quasi-menacées (NT) (6%), 27 espèces en préoccupation mineure (LC) (18 %) et 68 espèces en données insuffisantes (DD) (46%). Dans le cadre de la mise en place d’une politique de gestion conservatoire de la biodiversité, des mesures devront être prise rapidement par les autorités locales, afin d’assurer la conservation de ces espèces dont certaines sont en danger d’extinction.

   

INTRODUCTION

Located in the Indian Ocean, the Comoros archipelago consists of four volcanic islands: Grande Comoros, Anjouan, Mohéli, and Mayotte (Figure 1). The first three are under Comorian authority, while Mayotte is under French administration. It has undergone several biological migrations, generally originating from the East African coast and neighboring islands (Madagascar, the Mascarene Islands, etc.).

This archipelago and all the islands of the southwestern Indian Ocean are among the world’s biodiversity hotspots (Dorr, L. J., 1997; Labat J. et al., 2010), particularly for orchids. Orchids form the royal family of the plant kingdom (Stewart and Griffiths, 1995; Gravendeel et al., 2004), with over 25,000 species, of which approximately 1,000 are found in the Indian Ocean region. More than 1,000 species, distributed among 65 genera, are native to Madagascar and the surrounding islands: the Comoros, Mascarene Islands, and Seychelles (Benny et al., 2019), and are found in numerous climatic zones around the globe. These entomophilous flowering plants are highly evolved. For example, in the genus Aerangis, a total of 58 species, including three natural hybrids, are currently recognized. They are distributed throughout tropical and southern Africa, Madagascar, the Comoros, Réunion, and Sri Lanka. Thirty-one species and two varieties are found in continental Africa, none of which are present in the islands of the Indian Ocean. Most sub-Saharan African countries are home to at least one species, with the largest number found in Tanzania, where 19 species have been recorded, followed by Kenya and Malawi, with 10 species each (La Croix 2022). In addition, 27 species have been identified in the western Indian Ocean region, namely Madagascar, the Comoros, and Réunion; all are endemic.

Twenty of these are endemic to Madagascar, three to the Comoros only, three to both the Comoros and Madagascar, and one, Aerangis punctata, to both Madagascar and Réunion. No species have been reported on the other islands of the western Indian Ocean. The orchids of the Comoros archipelago include endemic, native, and threatened species. The La Grille and Karthala massifs are home to the majority of Comorian endemic species (more than 50% of orchids including 45 endemic species) (Rakotoarivelo F. et al., 2011).

However, knowledge of this flora has many gaps. No complete and up-to-date list of orchids from the entire archipelago exists to date. Works on the orchids of the Comoros Islands are old and partial: the work of Schlechter, R. (1915) in “Kritische Aufzählung der bisher von Madagaskar, den Maskarenen, Komoren und Seychellen bekanntgewordenen Orchidaceen”, that of PERRIER DE LA BÂTHIE (1939-1941) in the Flore de Madagascar et des Comores, and concern a small amount of material from old collections by Boivin & Humblot. The only recent work available to date is quite fragmentary and concerns only the study of a single genus (e.g., Jumellea) or a single species (e.g., Jumellea bosseri, Jumellea pailleri) (Bosser, J., 2002; Cribb, P. & Hermans, J., 2009; Neirynck and Herremans, 2006; Pailler et al., 2008; Pailler, 2009). Few studies have been conducted on the taxonomy of the genera. Since the last comprehensive revision by Perrier de la Bâthie (1939), eight new species of Jumellea have been legitimately described (Summerhayes 1952; Senghas 1964, Senghas 1967; Bosser 1970; Wood 1982; Cribb 2009; Herremans 2001; La Croix 2000; Pailler 2009).

Currently, only two orchid species (Jumellea anjouanensis and Angraecum humblotianum) are listed as threatened by the IUCN for Grande Comore, Anjouan, and Mohéli, both categorized as “endangered” (EN). All orchids are partially protected, without species specificity, on the list of protected species published in decree no. 01/031/MPE/CAB of May 14, 2001, concerning the protection of wild fauna and flora species in the Comoros (Louette, 2004).

On Grande Comore and Anjouan, terrestrial and marine protected areas are being developed, and Mohéli has a protected area, the Mohéli National Park. In Mayotte, a preliminary list of orchids already exists, categorized according to the IUCN (Barthelat et al., 2006; IUCN French Committee, 2013; Hervouet & Barthelat, 2014). Although the marine natural park was created in 2010 and protects the lagoon, its area is limited by the high tide mark (the upper limit of the public maritime domain) and therefore does not include terrestrial habitats. The existing species on the islet of Mbouzi have been protected since the creation of this 82-hectare islet as a nature reserve in 2007. To address this, this work consists of taking stock of the diversity and biogeography of orchids in the Comoros archipelago and determining the ecological status of each species.

Figure 1: Category (Endemism, Indigenous and Introduction)

MATERIALS AND METHODS

Three main methods were used in this work: literature reviews, ecological surveys, personal observations, and conservation status assessment:

– The literature reviews consisted of consulting all documents relating to our topic held in the libraries of national institutions (INRAPE library, CNDRS library) and international databases: the IRNAPE herbarium, the University of the Comoros herbarium, and international herbaria (National Museum of Natural History in Paris, Sonnerat, Tropicos-Misouri Botanical Garden, National Botanical Conservatory of the Mascarene Islands in Réunion and Mayotte).

– The spot ecological surveys and personal observations were carried out in two phases: June and July 2018 (first phase); January and March 2019 (second phase), during which field observations were made using the linear survey method (Duvigneaud, 1980) as well as the collection of samples and their placement in a herbarium at INRAPE.

– The assessment of the conservation status of the species was carried out according to the IUCN criteria and categories described in the two guides: the categories and criteria of the IUCN Red List, Version 3.1 (2012) (www.uicn.fr/La-Liste-rouge-des-especes.html) and the guidelines for the application of the IUCN Red List criteria at the regional and national levels, Version 4.0 (2012) (www.uicn.fr/La-Liste-rouge-des-especes.html); but also based on the Red List of the Flora of Mayotte (Barthelat et al., 2006; IUCN France, 2018; Hervouet & Barthelat, 2014).

RESULTS AND DISCUSSION

A- Results

  1. Floristic Diversity and Biological Spectrum
  2. Floristic Diversity

A total of 148 orchid species were recorded throughout the Comoros archipelago, distributed across 33 genera (Table 1).

The most represented genera are Angraecum (21 species and subspecies), Eulophia (17 species), Cynorkis (16 species and varieties), Bulbophyllum (14 species), Habenaria (9 species), Jumellea (8 species), Aerangis (7 species), Polystachya (6 species), Aeranthes, Disperis, Nervilia, and Liparis (5 species each) (Figure 2). In contrast, the other genera Angraecopsis, Benthamia, Bolusiella, Calanthe, Cheirostylis, Corymborkis, Cymbidiella, Didymoplexis, Galeola, Goodyera, Graphorkis, Hetaeria, Lemurella, Malaxis, Microcoelia, Microterangis, Neobathiea, Oberonia, Oeoniella, Platylepis, Satyrium, Vanilla, and Zeuxine are less represented, with one to three species each. Furthermore, the genera Acampe, Benthamia, Bolusiella, Calanthe, Corymborkis, Didymoplexis, Galeola, Graphorkis, Lemurella, Neobathiea, Oberonia, Oeoniella, Platylepis, and Stichorkis are monospecific.

Table 1: List of orchid species recorded in the Comoros archipelago (endemic species in bold) in the biography and some field observations

Espèce

Biogéographie

GC AN MO MA COM
1 Acampe pachyglossa INDI : COM, MADA, AFR & MAS (Reunion & Somalia) X X X X  
2 Aerangis bursiculata sp. nov END GC strict X        
3 Aerangis divitiflora END COM & MADA (centre ouest) X     X X
4 Aerangis hildebrandtii END COM X X X X X
5 Aerangis modesta END COM (GC & AN) &MADA X X     X
6 Aerangis polyura sp. nov END COM X X      
7 Aerangis rostellaris END COM (GC) & MADA X       X
8 Aerangis spiculata END COM (GC, AN &MA) et MADA X X   X  
9 Aeranthes campbelliae END GC strict X        
10 Aeranthes caudata

END COM & MADA

        X
11 Aeranthes dentiens END COM & MADA         X
12 Aeranthes grandiflora END COM &MADA         X
13 Aeranthes virginalis END COM & MADA         X
14 Angraecopsis pobeguinii END GC strict X        
15 Angraecopsis trifurca END COM & AFR (Ethiopia, Zimbabwe) X        
16 Angraecum arachnites MADA X        
17 Angraecum baronii MADA X       X
18 Angraecum calceolus INDI : MOZA in Western India (COM, MADA & MASC (MAU, ROD, REU, SEY) X X X    
19 Angraecum caulescens END COM & MASC X   X X  
20 Angraecum conchoglossum MADA, REU         X
21 Angraecum dendrobiopsis MADA         X?
22 Angraecum eburneum COM, AFR (Southe-ast Kenya to eastern Tanzania, Pemba and Zanzibar), MADA et MASC (MAU, REU, SEY) X        
23 Angraecum eburneum subsp. superbum INDI : COM, MADA & SEY X   X X  
24 Angraecum florulentum END COM X X?      
25 Angraecum germinyanum END COM & REU X X   X X
26 Angraecum humbertii MADA         X
27 Angraecum humblotianum MADA         X
28 Angraecum leonis END COM & MADA X   X X X
29 Angraecum mauritianum MADA, MASC X X?      
30 Angraecum meirax END COM et MADA         X
31 Angraecum multiflorum MADA, MASC (MAU, REU, SEY) & COM         X
32 Angraecum pectinatum INDI : COM, MADA & MASC (MAU, REU)     X   X
33 Angraecum sp IND X        
34 Angraecum scottianum END COM X X      
35 Angraecum xylopus END COM X       X
36 Benthamia sp IND X        
37 Bolusiella iridifolia INDI : COM &AFR         X
38 Bulbophyllum alexandrae MADA & COM         X
39 Bulbophyllum comorianum END COM X        
40 Bulbophyllum coriophorum END COM &MADA X ?   X X  
41 Bulbophyllum densum MASC (MAU &REU)         X
42 Bulbophyllum humblotii MADA, SEY & AFR (Tanzania, Zimbabwe), Malawi et COM X        
43 Bulbophyllum hyalinum END GC &MADA X        
44 Bulbophyllum intertextum AFR, MADA, SEY X       X
45 Bulbophyllum leonii END COM X X X    
46 Bulbophyllum longiflorum Uganda, northeast of KwaZulu-Natal, west of the Indian Ocean, from Bhutan to the Pacific. X   X X  
47 Bulbophyllum megalonyx END COM   X      
48 Bulbophyllum nutans INDI : COM, MADA &MASC (MAU, REU) X        
49 Bulbophyllum occlusum MADA, REU & COM        
50 Bulbophyllum occultum INDI : COM, MADA & MASC (MAU, REU) X   X    
51 Bulbophyllum sp IND X X      
52 Calanthe sylvatica INDI : COM, AFR et west OI (MADA & REU) X X X X  
53 Cheirostylis nuda MAU, REU     X    
54 Cheirostylis gymnochiloides END COM (AN & MA) &MADA     X X  
55 Corymborkis corymbis AFR, MADA et REU         X
56 Cynorkis benaraensis sp. nv. END COM (MA)       X  
57 Cynorkis comorensis END GC strict X        
58 Cynorkis fastigiata INDI : COM, MADA &MASC (MAU, REU & SEY) X X X X  
59 Cynorkis flexuosa END MA & MADA       X  
60 Cynorkis nutans COM, MADA & REU X        
61 Cynorkis humblotiana END COM         X
62 Cynorkis lilacina INDI : COM, MADA & REU X X      
63 Cynorkis lilacina var. boiviniana END COM X        
64 Cynorkis lilacina var. comorensis END COM X X      
65 Cynorkis parvula END COM         X
66 Cynorkis purpurascens INDI : COM (MA), MADA & MASC       X  
67 Cynorkis ridleyi COM, MADA & REU X       X
68 Cynorkis schmidtii END GC Strict X        
69 Cynorkis sigmoidea END GC strict X        
70 Cynorkis speciosa MADA       X  
71 Cynorkis tenella END COM & MADA X        
72 Didymoplexis avaratraensis Madagascar       X  
73 Disperis hildebrandtii END COM & MADA       X  
74 Disperis humblotii END COM & MADA X X     X
75 Disperis oppositifolia INDI : Comoros, Madagascar, Mauritius, Réunion X   X X  
76 Disperis trinileata END COM & MADA   X   X  
77 Disperis tripetaloides IND   X   X X
78 Eulophia alismatophylla  END COM & MADA (N.E)         X
79 Eulophia angornensis END COM         X
80 Eulophia bosseriana M.W.Chase & Schuit.

MADA (SW. & S. Central)

      X  
81 Eulophia cordylinophylla END COM X   X X  
82 Eulophia cucullata INDI : COM, AFR &MADA X     X  
83 Eulophia decaryana 

INDI : COM, AFR (Kenya, KwaZulu-Natal, MOZ, Zimbabwe) & MADA,

      X ? X ?
84 Eulophia falcigera  MADA         X ?
85 Eulophia furcata  END COM et MADA (NW)       X  
86 Eulophia livingstoneana INDI : COM, AFR (Ethiopia to Limpopo) & MADA X     X  
87 Eulophia lonchophylla  END COM et AFR (KwaZulu-Natal, MOZ, Tanzania) X   X X  
88 Eulophia maculata 

IND : COM, AFR, MADA & MAU

      X X
89 Eulophia petiolata  END COM &MADA (N.W)       X X
90 Eulophia pileata END COM & MADA         X
91 Eulophia plantaginea IND X     X  
92 Eulophia pulchra  INDI : COM, AFR (Tanzania à MOZ), MADA, MAU and W. Pacific.       X X
93 Eulophia sclerophylla  END COM et MAD (SE)         X
94 Eulophia spathulifera H. Perrier N. & W. MADA       X X
95 Eulophia sp END COM        X  
96 Galeola humblotii END COM (GC) et MADA X        
97 Goodyera afzelii MADA, MOZ, Vietnam X      
98 Goodyera procera Tropical and Subtropical Asia     X   X
99 Graphorkis concolor INDI : COM, MADA, MASC (MAU, REU, SEY)         X
100 Graphorkis concolor var. alphabetica INDI : COM, MADA, MADA (MAU, REU, SEY)       X  
101 Habenaria boiviniana INDI : COM, AFR (Kenya, Tanzania,) &MADA X   X X  
102 Habenaria cirrhata INDI : COM, Tropical AFR and MADA         X
103 Habenaria clareae MADA, Malawi, Zimbabwe       X  
104 Habenaria comorensis END COM         X
105 Habenaria incarnata END COM &MADA X X ? X   X
106 Habenaria johannae END COM   X      
107 Habenaria sp IND X X X    
108 Habenaria tomentella END COM         X
109 Hetaeria vaginalis END COM         X
110 Jumellea anjouanensis END COM X X X   X
111 Jumellea arachnantha END COM X X X X ?  
112 Jumellea arborescens END COM & MADA X   X X  
113 Jumellea comorensis END COM X X     X
114 Jumellea confusa END COM & MADA         X
115 Jumellea maxillarioides END COM & MADA X        
116 Jumellea pailleri END COM X X      
117 Jumellea sp IND X X X    
118 Lemurella culicifera INDI : COM, MADA, MAU X X   X  
119 Liparis caulescens REU X       X
120 Liparis cespitosa INDI : COM, Tanzania to MOZ & S. Pacific X       X
121 Liparis salassia INDI : COM, MADA, MAU, REU         X
122 Liparis sambiranoensis END COM et MADA   X X X X
123 Liparis sp IND   X X    
124 Malaxis cardiophylla END COM X     X X
125 Microcoelia aphylla INDI : COM, AFR (Kenya, KwaZulu-Natal, MOZ, Tanzania, Uganda, Zimbabwe), MADA et MASC (REU et MAU)       X
126 Microcoelia cornuta END COM et MADA (N.O)       X X
127 Microcoelia macrantha

MADA

X     X  
128 Neobathiea grandidieriana END COM et MADA X X     X
129 Nervilia bicarinata INDI : COM, AFR, MAD et Arabian Peninsula X     X  
130 Nervilia hirsuta IND       X X
131 Nervilia kotschyi INDI : COM, AFR et MADA  X     X  
132 Nervilia petraea Tropical AFR       X  
133 Nervilia renschiana AFR (Tanzania to South Africa) & MADA       X  
134 Oberonia disticha INDI : Tropical AFR &S. Africa & West OI X X X    
135 Oeoniella polystachys INDI : COM, MADA & MASC (MAU, REU) X       X
136 Platylepis polyadenia INDI : COM, MADA, MASC (MAU, REU, SEY) X   X X X
137 Polystachya anceps END COM et MADA X X   X  
138 Polystachya concreta INDI : Tropical & Subtropical America. X X X X  
139 Polystachya cultriformis INDI : COM, Tropical et S. Africa et west OI X X ?     X
140 Polystachya rosea END COM, MADA & SEY X       X
141 Polystachya sp IND X X      
142 Polystachya waterlotii END COM & MADA (Centrale)   X     X
143 Satyrium amoenum INDI : COM, MADA, REU X        
144 Satyrium trinerve IND : COM, AFR (Tropical et S. Afrique) & MADA X        
145 Stichorkis disticha END COM, MASC (MAU et REU) X        
146 Vanilla humblotii END COM & MADA (N) X X   X  
147 Vanilla planifolia INTR : S. Mexico to N. Brazil X X X X  
148 Zeuxine ballii Malawi to Zimbabwe       X  

Indication :

GC: Grand Comoros (Ngazidja); AN: Anjouan (Ndzuani); MO: Moheli (Mwali); MA: Mayotte (Maoré). MADA: Madagascar; AFR: Africa; REU: Reunion; MAU: Mauritius; SEY: Seychelles; MOZ: Mozambique.

END: Endemic; INDI: Native; INTR: Introduced; IND: Undetermined; ?: Presence doubtful.

b- Biological spectrum, epiphyte substrate, and habitat

Three biological forms can be distinguished according to Raunkiaer’s (1906) biological spectrum in the orchids of the Comoros Archipelago (Table 2): epiphytes (on tree trunks, lithophytes, or saxicolous) represent approximately 54%, geophytes (terrestrial orchids) approximately 46%, and lianas only 1%.

It should also be noted that, depending on the climate and vegetation type, most of the recorded orchids are found primarily in humid and transitional forests or savannas (151 species), compared to 5 species in dry areas (forest, scrubland, and savanna). The humid climate and vegetation type of the sites play very important roles in the establishment of these species, most of which are epiphytes. However, some species with very high ecological plasticity in these islands can be found in both humid and dry forests (examples: Angraecum humblotianum, Bulbophyllum hyalinum, etc.). The Comoros, located in the tropics, boasts a wide diversity of flowers, including orchids. Most often, they grow on trees, but some also grow on rocks.

Several species of trees and shrubs are used as supports by epiphytic orchid species in the vegetation formations of the archipelago. In humid forests and mesophyll forests, the species found are Weinmannia comorensis (Cunoniaceae), Ophiocolea comorensis (Bignoniaceae), Aphloia theaeformis (Flacourtiaceae), and Tambourissa leptphylla (Monimiaceae). In dry forests, thickets, and fields, the species found are Vitex doniana (Verbenaceae) and Mangifera indica (Anacardiaceae).

2-Table : Biological spectra of orchids

Biological spectra Epiphyt Geophyt Liana Total
Number of species 80 68 2 148
Biological form rate (%) 54 46 1,28 100

2- Biogeographical Affinity of Species and Endemism

The flora of these islands shares similarities due to their origin (islands of the Indian Ocean). However, there is a disparity in the distribution of endemic species and their presence on each island (Table 3). Grande Comore has the highest proportion of endemic species despite its relatively young age.

Table 3 : Distribution of endemic species and their presence on each island

Specie Biogeography GC AN MO MA COM
1 Aerangis bursiculata sp. nov END GC strict X        
2 Aerangis divitiflora END COM &MADA (West-Center) X     X X
3 Aerangis hildebrandtii END COM X X X X X
4 Aerangis modesta END COM (GC et AN) & MADA X X     X
5 Aerangis polyura sp. nov END COM X X      
6 Aerangis rostellaris END COM (GC) & MADA X       X
7 Aerangis spiculata END COM (GC, AN et MA) & MADA X X   X  
8 Aeranthes campbelliae END GC strict X        
9 Aeranthes caudata END COM & MADA         X
10 Aeranthes dentiens END COM & MADA         X
11 Aeranthes grandiflora END COM & MADA         X
12 Aeranthes virginalis END COM & MADA         X
13 Angraecopsis pobeguinii END GC strict X        
14 Angraecopsis trifurca END COM &AFR (Ethiopia, Zimbabwe) X        
15 Angraecum caulescens END COM & MASC X   X X  
16 Angraecum florulentum END COM X X?      
17 Angraecum germinyanum END COM & REU X X   X X
18 Angraecum leonis END COM & MADA X   X X X
19 Angraecum meirax END COM & MADA         X
20 Angraecum scottianum END COM X X      
21 Angraecum xylopus END COM X       X
22 Bulbophyllum comorianum END COM X        
23 Bulbophyllum coriophorum END COM & MADA X ?   X X  
24 Bulbophyllum hyalinum END GC & MADA X        
25 Bulbophyllum leonii END COM X X X    
26 Bulbophyllum megalonyx END COM   X      
27 Cheirostylis gymnochiloides END COM (AN, MA), MADA     X X  
28 Cynorkis benaraensis sp. nv. END COM (MA)       X  
29 Cynorkis comorensis END GC strict X        
30 Cynorkis flexuosa END MA et MADA       X  
31 Cynorkis humblotiana END COM         X
32 Cynorkis lilacina var. boiviniana END COM X        
33 Cynorkis lilacina var. comorensis END COM X X      
34 Cynorkis parvula END COM         X
35 Cynorkis ridleyi            
36 Cynorkis schmidtii END GC Strict X        
37 Cynorkis sigmoidea END GC strict X        
38 Cynorkis tenella END COM &MADA X        
39 Disperis hildebrandtii END COM &MADA       X  
40 Disperis humblotii END COM & MADA X X     X
41 Disperis trinileata END COM &MADA   X   X  
42 Eulophia alismatophylla  END COM &MADA (N.E)         X
43 Eulophia angornensis END COM         X
44 Eulophia cordylinophylla END COM X   X X  
45 Eulophia furcata  END COM & MADA (NW)       X  
46 Eulophia lonchophylla  END COM & AFR (KwaZulu-Natal, MOZ, Tanzania) X   X X  
47 Eulophia petiolata  END COM & MADA (N.W)       X X
48 Eulophia sclerophylla  END COM &MAD (SE)         X
49 Eulophia sp END COM        X  
50 Galeola humblotii END COM (GC) & MADA X        
51 Habenaria comorensis END COM         X
52 Habenaria incarnata END COM & MADA X X ? X   X
53 Habenaria johannae END COM   X      
54 Habenaria tomentella END COM         X
55 Hetaeria vaginalis END COM         X
56 Jumellea anjouanensis END COM X X X   X
57 Jumellea arachnantha END COM X X X X ?  
58 Jumellea comorensis END COM X X     X
59 Jumellea confusa END COM et MADA         X
60 Jumellea maxillarioides END COM & MADA X        
61 Jumellea pailleri END COM X X      
62 Liparis sambiranoensis END COM & MADA   X X X X
63 Malaxis cardiophylla END COM X     X X
64 Microcoelia cornuta END COM &MADA (N.O)       X X
65 Neobathiea grandidieriana END COM &MADA X X     X
66 Polystachya anceps END COM &MADA X X   X  
67 Polystachya rosea

END COM, MADA & SEY

X       X
68 Polystachya waterlotii END COM & MADA (Center)   X     X
69 Stichorkis disticha END COM, MASC (MAU & REU) X        
70 Vanilla humblotii END COM & MADA (N) X X   X  

Figure 1 shows that of the 148 orchid species inventoried for all 4 islands of the archipelago, 70 species (i.e. 47%) are endemic, 72 are native or naturalized (i.e. 49%), 5 are undetermined (i.e. 3%) and only one introduced species (i.e. 1%).

Endemic species are distributed as follows:

– 34 species are endemic to the Comoros and Madagascar (i.e., 92%), 2 species are endemic to the Comoros and the Mascarene Islands (i.e., 5%), and only one species is endemic to the Comoros and Africa (i.e., 3%) (Fig. 2). Thus, the species are much more closely related between the Comoros and Madagascar than with Africa and the Mascarene Islands.

– 31 are endemic to the Comoros, of which seven (7) are strictly endemic to Grande Comore and two (2) strictly endemic to Anjouan.

 

Figure 2: Affinity of the Comoros endemic species with Madagascar, Africa, and the Mascarene Island

3- Ecological status of the species

The threats to the habitats of the studied species are both anthropogenic and natural in origin; however, it is the anthropogenic threat that contributes most to the destruction of these species’ habitats and leads to a reduction in forest area, as the majority of the species are forest dwellers. Indeed, the IUCN classification takes into account relationships with neighboring populations to avoid inappropriate estimates, for example, estimates that could be overestimated for populations at the edge of their range (Feldmann, 2008). Literature reviews, field data, analysis of the distribution map of selected species, and the threats and pressures exerted on species and habitats allowed for an estimation of extinction risks for all selected species, given the lack of well-defined and structured terrestrial Protected Areas in the archipelago. The area of ​​occurrence is less than 400 km² and the area of ​​occupancy is less than 80 km². Fifteen (15) species are categorized as Critically Endangered (CR) (10%), 7 species as Endangered (5%), 24 as Vulnerable (VU) (16%), 9 as Near Threatened (NT) (6%), 27 as Least Concern (LC) (18%), and 68 species do not allow for a threat category to be proposed according to the Red List criteria due to a lack of data (DD) (46%) (Table 4). This does not mean that they are not threatened or of special interest, but rather that particular attention must be paid to them to better assess their status.

4-Table : Ecological status of orchids according to IUCN criteria

Species – Author – Publication Date Statut
1 Aerangis bursiculata Hermans sp. nov CR
2 Aerangis polyura sp. nov CR
3 Bulbophyllum hyalinum Schltr., 1924 CR
4 Bulbophyllum intertextum Lindl., 1862 CR
5 Cynorkis comorensis Bosser., 2002 CR
6 Cynorkis lilacina Ridl. CR
7 Cynorkis lilacina Ridl. var. boiviniana (Kraenzl.) H. Perrier CR
8 Graphorkis concolor (Thouars) Kuntze.,1891 CR
9 Graphorkis concolor (Thouars) Kuntze var. alphabetica F. N. Rasm.,1979 CR
10 Habenaria clareae Hermans., 2007 CR
11 Eulophia maculata (Lindl.) Rchb.f.1863 CR
12 Liparis caulescens Cordem., 1895 CR
13 Liparis cespitosa (Lam.) Lindl., 1825 CR
14 Nervilia renschiana Rchb.f., 1881 CR
15 Stichorkis disticha (Thouars) Pfitzer., 1897 CR
1 Didymoplexis avaratraensis P. J. Cribb, Nusb. & L. Gaut., 2012 EN
2 Eulophia livingstoneana (Rchb. f.) Summerh., 1948 EN
3 Goodyera afzelii Schltr., 1918 EN
4 Jumellea pailleri F.Rakotoar., 2011 EN
5 Malaxis cardiophylla (Rchb.f.) Kuntze., 1891 EN
6 Microcoelia macrantha (H. Perrier) Summerh., 1943 EN
7 Nervilia petraea (Afzel. Ex.Sw) Summerth., 1945 EN
1 Aerangis modesta (Hook. f.) Schltr., 1914 VU
2 Angraecopsis trifurca (Rchb. f.) Schltr., 1915 VU
3 Angraecum calceolus Thouars., 1822 VU
4 Angraecum caulescens Thouars., 1822 VU
5 Angraecum eburneum Bory., 1804 VU
6 Angraecum florulentum Rchb. F., 1885 VU
7 Angraecum germinyanum Hook. f., 1889 VU
8 Angraecum scottianum Rchb. f.,1878 VU
9 Angraecum leonis (Rchb. f.) André., 1885 VU
10 Bulbophyllum nutans Thouars., 1822 VU
11 Bulbophyllum occultum Thouars., 1822 VU
12 Cynorkis benaraensis sp. nv. VU
13 Cynorkis sigmoidea Kraenzl.,1898 VU
14 Galeola humblotii Rchb.f., 1885 VU
15 Jumellea maxillarioides (Ridl.) Schltr.,1925 VU
16 Jumellea arborescens H. Perrier., 1938 VU
17 Microcoelia aphylla (Thouars) Summerh., 1936 VU
18 Microcoelia cornuta (Ridl.) Carlsward., 2007 VU
19 Nervilia bicarinata (Blume) Schltr., 1911 VU
20 Nervilia kotschyi (Rchb. f.) Schltr., 1911 VU
21 Eulophia cordylinophylla Rchb.f. 1885 VU
22 Platylepis polyadenia Rchb. f., 1885 VU
23 Satyrium trinerve Lindl., 1838 VU
24 Vanilla humblotii Rchb. f., 1885 VU
1 Angraecum eburneum subsp. superbum NT
2 Bulbophyllum comorianum H. Perrier., 1838 NT
3

Calanthe sylvatica (Thouars) Lindl., 1883

NT
4 Cynorkis fastigiata Thouars., 1822 NT
5 Cynorkis purpurascens Thouars., 1822 NT
6 Disperis oppositifolia Sm., 1809 NT
7 Eulophia pulchra Eulophia pulchra (Thouars) Lindl.1883 NT
8 Eulophia furcata furcata (Bosser & Morat) MWChase & Schuit.2021 NT
9 Polystachya cultriformis (Thouars) Lindl. ex Spreng., 1826 NT
1 Acampe pachyglossa Reichb. f. 1881 LC
2 Aerangis hildebrandtii (Rchb.f.) P.J.Cribb & Carlsward., 2012 LC
3 Angraecopsis trifurca (Rchb. f.) Schltr., 1915 LC
4 Bulbophyllum coriophorum Ridl., 1886 LC
5 Bulbophyllum leonii Kraenzl. 1900 LC
6 Bulbophyllum longiflorum Thouars., 1822 LC
7 Bulbophyllum nutans Thouars., 1822 LC
8 Bulbophyllum occultum Thouars., 1822 LC
9 Cheirostylis gymnochiloides (Ridl.) Rchb.f., 1885 LC
10 Cynorkis flexuosa Lindl., 1835 LC
11 Disperis hildebrandtii Rchb. f., 1881 LC
12 Disperis tripetaloides (Thouars) Lindl., 1839 LC
13 Eulophia alismatophylla Rchb.f.,1885 LC
14

Eulophia lonchophylla (Rchb. f.) Garay et Taylor., 1976

LC
15 Habenaria boiviniana Kraenzl. & Schltr., 1898/1897 LC
16 Habenaria incarnata (Lyall ex Lindl.) Rchb. f., 1865 LC
17 Jumellea anjouanensis (Finet) H. Perrier., 1941 LC
18 Jumellea arachnantha (Rchb. f.) Schlecht., 1915 LC
19 Jumellea comorensis (Rchb. f.) Schltr., 1915 LC
20 Lemurella culicifera (Rchb.f.) H. Perrier., 1941 LC
21 Liparis sambiranoensis Schltr., 1924 LC
22 Oberonia disticha (Lam.) Schltr., 1924 LC
23 Oeceoclades sp. LC
24 Oeoniella polystachys (Thouars) Schltr.1918 LC
25 Polystachya anceps Ridl., 1885 LC
26 Vanilla planifolia B. D. Jacks. ex Andrews., 1808 LC
27

Zeuxine ballii P.J.Cribb., 1977

LC
1

Aerangis divitiflora (Schltr.) P.J.Cribb & Carlsward.2012

DD
2 Aerangis rostellaris (Rchb.f.) H.Perrier.,1941 DD
3 Aerangis spiculata (Finet) Senghas., 1972 DD
4 Aeranthes campbelliae Hermans & Bosser., 2003 DD
5 Aeranthes caudata Rolfe ., 1901 DD
6 Aeranthes dentiens Rchb.f., 1885 DD
7 Aeranthes grandiflora Lindl., 1824 DD
8 Aeranthes virginalis D.L.Roberts., 2005 DD
9 Angraecopsis pobeguinii (Finet) H. Perrier., 1941 DD
10 Angraecum arachnites Schltr., 1925 DD
11 Angraecum baronii (Finet) Shltr., 1905 DD
12 Angraecum conchoglossum Schltr.,1918 DD
13 Angraecum dendrobiopsis Schltr., 1925 DD
14 Angraecum humbertii H.Perrier.,1939 DD
15 Angraecum humblotianum Schltr., 1915 DD
16 Angraecum mauritianum (Poir.) Frappier., 1880 DD
17 Angraecum meirax (Rchb.f.) H.Perrier.,1938 DD
18 Angraecum multiflorum Thouars., 1822 DD
19 Angraecum pectinatum Thouars., 1822 DD
20 Angraecum ramosum Thouars., 1822 DD
21 Angraecum sp DD
22 Angraecum xylopus Rchb.f., 1885 DD
23 Benthamia sp DD
24 Bolusiella iridifolia (Rolfe) Schltr. Beih.,1918 DD
25 Bulbophyllum alexandrae Schltr., 1925 DD
26 Bulbophyllum humblotii Rolfe., 1891 DD
27 Bulbophyllum densum Thouar., 1822 DD
28 Bulbophyllum occlusum Ridl., 1885 DD
29 Bulbophyllum megalonyx Rchb.f., 1881 DD
30 Bulbophyllum sp. DD
31 Cheirostylis nuda Thouars., 1822 DD
32 Corymborkis corymbis Thouars., 1822 DD
33 Cynorkis humblotiana Kranszl., 1901 DD
34 Cynorkis lilacina Ridl. Var. comorensis H. Perrier DD
35 Cynorkis parvula Schltr., 1915 DD
36 Cynorkis ridleyi T. Durand & Schinz., 1895 DD
37 Cynorkis speciosa Ridl., 1885 DD
38 Cynorkis tenella Ridl., 1886 DD
39 Disperis humblotii Rchb. f., 1885 DD
40 Disperis trinileata Schltr., 1924 DD
41 Eulophia alismatophylla Rchb.f.1885 DD
42 Eulophia angornensis (Rchb.f.) P.J.Cribb., 1998 DD
43 Eulophia bosseriana M.W. Chase & Schuit.2021 DD
44 Eulophia decaryana H.Perrier. 1935 DD
45

Eulophia falcigera (Rchb.f.) MWChase, Kumar et Schuit.

DD
46 Eulophia pileata Ridl., J. Linn., 1885 DD
47 Eulophia plantaginea (Thouars) Rolfe ex Hochr., 1908 DD
48 Eulophia sclerophylla Rchb.f.1885 DD
49 Eulophia spathulifera H.Perrier. 1935 DD
50 Eulophia sp DD
51 Goodyera procera (Ker Gawl.) Hook., 1923 DD
52 Habenaria cirrhata (Lindl.) Rchb.f., 1865 DD
53 Habenaria comorensis H. Perrier., 1951 DD
54 Habenaria johannae Kranze., 1893 DD
55 Habenaria sp DD
56 Habenaria tomentella Rchb., 1885 DD
57 Hetaeria vaginalis Rchb.f., 1885 DD
58 Jumellea confusa (Schltr.) Schltr., 1915 DD
59 Jumellea sp DD
60 Liparis salassia (Pers.) Summerh., 1953 DD
61 Liparis sp DD
62 Neobathiea grandidieriana (Rchb.f.) Garay., 1972 DD
63 Nervilia hirsuta(Blume) Schltr., 1911 DD
64 Oeoniella polystachys (Thouars) Schltr., 1918 DD
65 Polystachya rosea Ridl., 1885 DD
66 Polystachya sp DD
67 Polystachya waterlotii Guillaumin., 1928 DD
68

Satyrium amoenum (Thouars) A. Rich., 1828

DD

Discussion

1- Floristic Diversity and Endemism

The terrestrial ecosystems of the Comoros archipelago include rainforests in the mountainous regions of each island and dry forests. Altitude and soil have contributed to a high level of diversity, including several endemic and threatened species, among them many orchids. The number of orchid species inventoried during this study is very high (33 genera, 144 species, 1 subspecies, and 3 varieties of orchids, with 70 endemic taxa), compared to previous studies, as shown in Tables 1 and 4. It should be noted that Moulaert (1998) adopted the number of species from Perrier de la Bathie (1939, 1941), adding 3 species, and Pailler et al. (2018) cited 28 endemic species (Table 5). Since 1915, inventories carried out mainly in Mayotte, to a lesser extent in Grande Comore, and very little in Anjouan and Mohéli, have led to the discovery of several species, some of which are new to science. Revision by genus has also contributed to finding more and more new species. In addition, other species have been synonymized (e.g., Microterangis hariotiana, Solenangis cornuta, etc.), as mentioned by Kaith et al. (2006).

For example, two new genera have just been added to our list: Didymoplexis (with the species D. avaratraensis, a species that until now had only been found in Madagascar and which has just been rediscovered in Mayotte) and Zeuxine, an African genus (with the species Z. balli, which does not exist in Madagascar).

Table 5: Comparison of orchids inventoried from 1905 to 2006.

  Schlechter R (1915) Perrier de la Bathie (1939, 1941) Moulaert (1998) Keith, Abdou and Labat (2006)
Number of genera 17 26 26 25
Number of species 46 69 72 81

Number of endemic species

41 45 45 18

2- Biogeography of Species

The insularity of the Comoros archipelago, its location in the tropics, allows it to have floristic affinities with neighboring countries. However, these affinities are stronger with Madagascar than with the African and Asian continents or the Mascarene Islands, as demonstrated by Rakotoarivelo et al. (2013) for the genus Jumellea Schltr. For example, the genus Disperis comprises nearly 80 species distributed in Africa, Madagascar, and the islands of the Indian Ocean (La Croix et al. 2002; Kurzweil and Manning, 2005; Govaerts, 2019), including 3 species native to the Comoros and Madagascar. None of these species are shared between the Comoros and Africa. The flora of the archipelago is very similar to that of Madagascar (with variations specific to each island) and can be considered a less diverse version of the main island (Louette et al., 2004). According to Pascal et al. (2001), one of the striking features of Mayotte’s flora is the considerable proportion of Malagasy plants, which are three times more numerous than plants of African origin.

From a botanical point of view, Mayotte is merely an extension of Madagascar. Recently, some thirty tree species previously considered endemic to Madagascar have been found in Mayotte, reinforcing the dominance of Malagasy plants on the island (Pascal, 2002). This could be due to the island’s biogeographical isolation from Africa, which is a continent.

Other factors may also play a role, such as prevailing winds, cyclones (which move from Madagascar to the Comoros), ocean currents, and animals. Indeed, oceanic islands formed by submarine volcanism, such as the Comoros Archipelago, exhibit a distinct originality in terms of plant biodiversity (biogeographical endemism), but also a relative poverty compared to the continental landmasses from which colonizing organisms originate (Abdillahi, 2017). For example, as the closest landmass to Réunion Island, Madagascar provided the majority of the seeds for the native plants currently inhabiting the island. A study conducted on Dombeyoidae clearly illustrates the multiple Malagasy origins of their species (Pechon et al., 2010).

3- Risk of Species Extinction

For a preliminary assessment, the results obtained in this study are broadly similar to those obtained for Réunion Island for 130 species assessed, including 9 critically endangered (CR) species (6%), 18 endangered (EN) species (12%), 9 vulnerable (VU) species (6%), 9 near threatened (NT) species (6%), 57 of least concern (LC) species (38%), and 43 with sufficient data (DD) species (27.7%) (http://www.reunion.developpement-durable.gouv.fr/IMG/pdf/Dossier de presse Flore vasculaire de La Réunion_cle567cb3). The destruction and degradation of natural habitats represent the main cause of the decline of plant species in Réunion.

Urban and agricultural development is responsible for the progressive disappearance of numerous species. Furthermore, some plant species are subject to intense harvesting pressure.

Due to their beauty, several orchid species are harvested for commercial purposes (http://www.reunion.developpement-durable.gouv.fr/IMG/pdf/Dossier de presse Flore vasculaire de La Réunion_cle567cb3). Throughout the islands of the Comoros archipelago, the original vegetation has undergone extreme decline. The proportion of land covered by forests fell from 6.6% in 1990 to 1.7% in 2012, meaning that nearly 500 hectares of forest disappear each year (FAO, 2010 and 2012) across the three islands. In Mayotte, natural formations now cover only 4 to 5% of the land area. Fragile ecosystems, such as dry forest, survive only in fragments. They have given way to slash-and-burn farming systems or the expansion of urban areas (Keith et al. 2006; Abdillahi, 2009 and 2017).

CONCLUSION

The Comoros archipelago is rich in plant biodiversity, particularly orchids. One hundred and forty-five species, one subspecies, and three varieties, distributed across 33 genera, were inventoried during this study. The most represented genera are Angraecum, Eulophia, Cynorkis, Bulbophyllum, Habenaria, Jumellea, Aerangis, Polystachya, and Aeranthes. Epiphytic and geophytic species are distributed almost equally (54% and 48%, respectively), with lianas representing only 1%. The majority of these orchids are found in humid and transitional forests and/or savannas, with very few in dry areas.

Seventy (70) species (47%) are endemic, 72 are native or naturalized (49%), 5 are undetermined (3%), and only one is an introduced species (1%), with variations between the islands. Grande Comore is the island richest in endemic species. These species are more closely related to Madagascar (47%) than to the African continent (3%), the Asian continent (1%), or the Mascarene Islands (2%).

Within this orchid flora, fifteen (15) species are critically endangered (CR) (8%), seven (7) are endangered (EN) (5%), 25 (25) are vulnerable (VU) (16%), nine (9) are near threatened (NT) (6%), 27 (27) are of least concern (LC) (18%), and 68 (46%) are of data deficient (DD). The habitats of these species are subject to various anthropogenic and natural pressures and threats, the former being the most significant.

This article aims to provide objective data to support conservation actions that could be integrated into management and conservation plans for the orchids of the archipelago, including the delimitation of these species’ habitats into protected areas and raising awareness among national and local authorities and the public about the biological and ecological importance of orchids. Further studies will be needed to further explore the ecology, diversity, and biogeography of these species in order to gain a comprehensive understanding of the orchids on each island of this archipelago.

Acknowledgments

We thank all those who supported us in conducting this field study and writing this article, in particular the Phytosociology and Geoarchitecture Laboratory at the University of Western Brittany and the SCAC service of the French Embassy in Moroni.

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Cite this Article:

Abdillahi, MM; Bioret, F; Boullet, V; Vennetier, E (2026). Contribution to the ecological study of orchids in the Comoros archipelago: floristic diversity, biogeography, ecological status, and conservation challenges. Greener Journal of Agricultural Sciences, 16(3): 123-140. https://doi.org/10.15580/gjas.2026.3.062426095 .

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