Seychelles Vegetation

Plant Formations in the Seychellean BioProvince

Peter Martin Rhind

Seychellean Mountain Moss Forest These humid moss or cloud forests are confined to the higher ridges of Mahé and Silhouette between altitudes of 550 and 880 m. Evergreen trees predominate with thick, leathery often strap-shaped leaves. The foliage often has a peculiar reddish or purplish tinge. This may include all of the leaves, as in the case of the endemic Randia ericea (Rubiaceae), or be confined to their under-surfaces as in the endemic Northea seychellarum (Sapotaceae). This together with the almost universal red bark and russet colour of epiphytic mosses gives the interior of these forests a gloomy somber appearance. Three stories can usually be distinguished. The canopy, which can reach heights of 16 m, is co-dominated by Neowormia ferruginea and Northea seychellarum. Other canopy trees include the endemic Campnospermum seychellarum (Anacardiaceae), Dillenia ferruginea (Dilleniaceae), Mimusops sechellarum (Sapotaceae), Northea hornei (Sapotaceae) and Vateria seychellarum (Dipterocarpaceae). The latter species is the only dipterocarp on the island and the only member of the Dipterocarpoidaea found outside of Australasia. A second story comprises several medium sized trees characteristic of which is the endemic palm Roscheria melanochoetes (Arecaceae), which in places can form pure stands. At higher altitudes this is typically jointed by the endemic tree Timonius sechellensis (Rubiaceae) and the two tall endemic shrubs Psychotria pervillei and P. sechellarum (Rubiaceae). However, at slightly lower elevations the main species include Colea peduculata, Randia lancifolia and the endemic Aphloia sechellensis (Aphloiaceae), Erythroxylum sechellarum (Erythroxylaceae), Eugenia wrightii (Myrtaceae), Indokingia crassa (Araliaceae), the endemic screw pines Pandanus multispicatus and P. sechellarum (Pandanaceae), and the endemic tree fern Cyathea sechellarum (Cyatheaceae). Other sub-canopy and shrub layer species include endemics like Canthium carinatum (Rubiaceae), Colea seychellarum (Bignoniaceae), Craterispermum microdon (Rubiaceae), Drypetes riseleyi (Putranjivaceae), Ficus bojeri (Moraceae), Gastonia sechellarum (Araliaceae), Gynura seychellensis (Asteraceae), Ixora pudica (Rubiaceae), Pittosporum wrightii (Pittosporaceae), Roscheria melanochaetes (Arecaceae), Tarenna sechellensis (Rubiaceae), Timonius sechellensis (Rubiaceae) and Verschaffeltia splendida (Arecaceae). At ground level, ferns such as Dryopteris wardii, Lindsaya kirkii, Nephrolepis biserrata, Polystichum adiantiforme and Vittaria scolopendrum are particularly prominent. Among the flowering plants there are beds of the endemic Curculigo sechellensis (Hypoxidaceae) and clumps of the endemic sedge-like Thoracostachyum floribundum (Cyperaceae). Other endemic herbs are Begonia seychellensis (Begoniaceae), Protarum sechellarum (Araceae), Thoracostachyum angustifolium (Cyperaceae), the pitcher plant Nepenthes pervillei (Nepenthaceae) and the rare saprophyte Seychellaria thomassetii (Triuridaceae).

Seychellean Sub-Montane or Intermediate Forest At lower elevations below the moss forest where the soils tend to be deeper, and mist and cloud less frequent, a taller more species rich forest is thought to have been widespread at one time, but much of this has now been destroyed. None of the original canopy appears to be intact, but it seems likely that it mainly comprised Neowormia ferruginea and the endemic Northea seychellarum (Sapotaceae) and Vateria sechellarum (Dipterocarpaceae). It is also not now possible to ascertain whether there were three or four stories, although much of the remaining evidence suggests the latter. Today conspicuous elements of the second story are the endemic Campnosperma sechellarum (Anacardiaceae) and the palm Verschaffeltia spendida (Arecaceae), both of which do not Copyright © 2010 Peter Martin Rhind extend into the moss forest. Less frequent second story species are Brexia madagascariensis, Riseleya griffithii and the endemic Craterispermum microdon (Rubiaceae), Soulamea terminalioides (Simaroubaceae) and Tarenna sechellensis (Rubiaceae). The third story comprises small trees and saplings although there appear to be few if any species that only grow at this level. The endemic palms Nephrosperma vanhoutteana, Phoenicophorium sechellarum and Rosheria melanochaeta (Areaceae) commonly occur while other species include the endemic Canthium bibracteatum (Rubiaceae), Erythroxylum sechellarum (Erythroxylaceae), Indokingia crass (Araliaceae), Ixora pudica (Rubiaceae) and Maba (Diospyros) sechellarum (Ebenaceae). The fourth or ground layer comprises various herbs notably Begonia aptera and the endemic Impatiens gordoni (Balsaminaceae) and Senecio sechellensis (Asteraceae). The epiphytic flora is well developed but has fewer species than the moss forest and festoons of moss are absent. Lianas, on the other hand, are scarce although the endemic Geopanax procumbens (Araliaceae) is relatively common on Silhouette. On certain ridges of Mahé the two endemic trees Excoecaria benthamiana (Euphorbiaceae) and Mimusops sechellarum (Sapotaceae) form what appears to be a local association, while on several rocky knolls such as ‘sugar loaf’ hill above Grande Anse on Mahé, the endemic palm Deckenia nobilis (Arecaceae) characterizes another local association. The latter formation possibly represents an outlier of the palm forests of Praslin.

Seychellean Lowland Dry Forest In the least disturbed areas these forests support a number of endemic palms such as Deckenia nobilis, Lodoicea maldivica (on deeper soils), Nephrosperma vanhoutteana, Phoenicophorium borsigianum, and endemic pandanas such as Pandanus multispicatus, Pandanus sechellarum and Pandanus balfourii (on the coast). This is also the habitat of the strange Medusagyna oppositifolia (in the monotypic family Medusagynaceae). Growing to a height of about 9 m, it has a sinuous stem and a dense umbrella-shaped crown. The species is thought to be of considerable age and is possibly a surviving ancient relict of Gondanaland.

Seychellean Coco De Mer Palm Forest Forest dominated by the endemic coco de mer palm Lodoicea maldivica (Arecaceae), which incidentally has the largest seed in the world, is now largely confined to the Vallee De Mai on Praslin Island. This World Heritage sites includes several other endemic palms such as Deckenia nobilis, Nephroperma vanhoutteanum, Roscheria melanochaetes and Verschaffeltia splendida, while other endemic trees include Canthium bibracteatum (Rubiaceae), Dillenia ferruginea (Dilleniaceae), Erythroxylum sechellarum (Erythroxylaceae), Eugenia wrightii (Myrtaceae), Maba (Diospyros) sechellarum (Ebenaceae), Memecylon elaeagni (Melastomataceae) and the pandans Pandanus hornei, P. multispicatus and P. sechellarum (Pandanaceae). Common epiphytes include the ferns Asplenium nidus and Phymatodes scolopendria together with several introduced species like Philodendron. The ground layer in these forests is typically littered with the dry, dead remains of palm leaves preventing the development of an extensive ground flora. However, clumps of the endemic sedge Lophoschoenus hornei (Cyperaceae) may be found together with the strange endemic herb Hypoxidia rhizophylla (Hypoxidiaceae). The latter has tough strap-shapes leaves and a basal star-shaped flower, which varies in colour from yellow to maroon-brown.

Seychellean Glacis Vegetation This varies according to whether the exposed rocks are in the upland moist forest areas or lowland dry forest areas. Soils accumulate in pockets and fissures and largely consisting of quartz with variable amounts of peat. In the upland areas peat is more abundant and on

Copyright © 2010 Peter Martin Rhind Mahé the characteristic species include Dianella ensifolia and various endemic species such as Erythroxylon sechellarum (Erythroxylaceae), Excoecaria benthamiana (Euphorbiaceae), Lophoschoenus hornei (Cyperaceae), Memecylon eleagni (Melastomataceae), Mimusops sechellarum (Sapotaceae), Pandanus multispicatus, P. sechellarum (Pandanaceae) and Soulamea terminalioides (Simaroubaceae). At high altitudes the endemic Garnotia sechellensis (Poaceae), Nepenthes pervillei (Nepenthaceae) and Randia sericea (Rubiaceae) are more or less confined to this habitat. In the dryer lowland areas of Mahé were peat is less plentiful the curious endemic Medusagyne oppositifolia (Medusagynaceae) becomes one of the characteristic species. Associated taxa include many of the aforementioned species of moist glacis, but in addition other endemics such as Canthium bibracteatum (Rubiaceae), Curculigo seychellensis (Amaryllidaceae), Deckenia noblis (Arecaceae), Dillenia ferruginea (Dilleniaceae), Eugenia wrightii (Myrtaceae), Maba seychellarum (Ebenaceae), Nephrosperma vanhoutteana (Arecaceae), Phoenicophorium borsigianum (Arecaceae), Timonius sechellensis (Rubiaceae) and Vanilla phalaenopsis (Orchidaceae) may be present. However, in coastal areas many of these species are replaced by Pandanus balfourii, Sarcostemma viminale and the endemic Euphorbia pyrifolia (Euphorbiaceae), and Canthium bibracteatum becomes more abundant.

Seychellean Riverine Vegetation Many of the mountain ravines are humid boulder strewn areas with little soil due to the action of flowing water. This factor together the relatively low light levels make many of these ideal for bryophytes and ferns. On Mahé these include the giant fern Angiopteris erecta and the endemic tree fern Cyathea sechellarum (Cyatheaceae). Begonias are also well represented including the endemic Begonia seychellensis (Begoniaceae). However, in less shady areas the endemic groundsel Gynura seychellensis (Asteraceae) becomes more conspicuous. The scattered trees and shrubs are mainly those of the neighbouring forests but may also include the endemic Pandanus hornei (Pandanaceae). At lower elevations where ravines fan out there two species, Heritiera littoralis and the endemic Barringtonia racemosa (Lecythidaceae), that are virtually confined to this habitat.

Seychellean Freshwater Swamps Among the many reeds, sedges and grasses of freshwater swamps are Typha javanica, Cyperus articulatus, Eleocharis dulcis, Mariscus pennatus, Echinocloa colonum and Paspalum geminatum - while trees include Barringtonia racemosa. Water plants include Eichhornia crassipes, Ipomoea aquatica, Polygonum senegalense, and the two water ferns Acrostichum aureum and Ceratopteris cornuta are locally common.

Further information required.

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