Included here are the volcanic Comoros Islands, the coralline Aldabra Islands and several other west Indian Ocean islands including Cosmoledo, Fauquhar, Glorieusa and Providence.

Comoran Pemphis Bush

Mainly associated with low-lying very rough, sharp ‘champignon’ or pitted limestone, this formation is almost entirely composed of Pemphis acidula bushes. It is a distinctive sclerophyll scrub that often forms a narrow belt outlining mangrove areas. There are also broader belts along part of the lagoon coast and on part of the north coast and south coast west of Dune d’Messe. On Aldabra the few associated plant species include the Aldabran endemics Sideroxylon inerme (Sapotaceae) and more locally Vernonia aldabrensis (Asteraceae). Pemphis scrub is also an important vegetation type on Astove, Europa and Cosmoleda, but has a restricted distribution being found no further north than the southern Amirantes and Providence and is absent from the granitic Seychelles.

Comoran Mixed Scrub and Scrub Woodland

Comprising open broad-leaf evergreen formations this vegetation usually forms stands ranging from 3-5 m tall but can reach 7 m. It occupies large areas of the raised limestone islands and supports most of the endemic species. On Aldabra it contains about 50 species of shrubs and small trees. The most conspicuous of these are Apodytes dimidiata, Canthium bibracteatum, Euphorbis abbottii, Ficus avi-avi, F. consimilis, F. nautarum, F. thonningii, Maytenus senegalensis, Mystroxylon aethiopicum, Ochno ciliata, Pandanus vandermeeschii, Polysphaeria multiflora, Terminalia fatraea and the Aldabran endemics Erythroxylon acranthum (Erythroxylaceae), Grewia aldabrensis, G. salicifolia (Tiliaceae) and Sideroxylon inerme (Sapotaceae). Less frequent but still notable are Allophylus alnifolia, Dracaena reflexa, Guettarda speciosa, Jasminum elegans, Phyllanthus cheloniphorbe, Scaevola taccada, Sarcostemma viminea and the Aldabran endemics Acalypha claoxyloides (Euphorbiaceae), Clerodendron glabrum (Verbenaceae), Flacourtia ramontschii (Salicaceae), Secamone freyeri (Apocynaceae) and Terenna supra-axillaris (Rubiaceae). Among the field layer species are various herbs including several sedges and the conspicuous succulent Lomatophyllum borbonicum. On Aldabra, but no longer on other islands, several species of this formation are browsed by tortoises and there is often a distinct browse line at about 0.6 m. Many of the trees seem to be arranged in rows and generally lean in a westward direction. This curious arrangement is thought to be due to the prevailing Trade Winds.

References

Battistini, R. & Cremers, G. 1972. Geomorphology and vegetation of Iles Glorieuses. Atoll Research Bulletin, No. 159.

Fosberg, F. R. 1971. Preliminary survey of the Aldabra vegetation. Philosophical Transaction of Royal Society, London, B260: 215-225.

Gillham, M. E. 1977a. Vegetation of sea and shore-bird colonies on Aldabra Atoll. Atoll Research Bulletin, 200: 1-19.

Hemsley, W. B. 1916. Flora of Seychelles and Aldabra. Journal of Botany, 54: 1-24.

Hemsley, W. B. 1919. Flora of Aldabra: with notes on the flora of the neighbouring islands. Kew Bulletin of Miscellaneous Information, 108-153.

Hemsley, W. B. & Turrill, W. B. 1917. Plants of Seychelles and Aldabra. Journal of Botany, 55: 285-288.

Hnatiuk, R. J. & Merton, L. F. H. 1979. Vegetation of Aldabra, a reassessment. Atoll Research Bulletin, 239: 1-22.

Stoddart, D. R. (ed). 1970. Coral Islands of the Western Indian Ocean. Atoll Research Bulletin, No. 136.

Stoddart, D. R. & Fosberg, F. R. 1984. Vegetation and floristics of western Indian Ocean coral islands. In: Biogeography and Ecology of the Seychelles Islands. Ed. D. R. Stoddart. Dr W. Junk Publishers.