Flora of St Helena

From Wikipedia, the free encyclopedia

The flora of St Helena, an isolated island in the South Atlantic Ocean, is exceptional in its high level of endemism and the severe threats facing the survival of the flora. ^[1]

Contents 1 Endemic and introduced flora 2 Vegetation 3 Human impact and conservation 4 List of endemic vascular plants of St Helena 5 Endemic genera 6 See also 7 External links 8 Footnotes and references 9 Further reading

[edit] Endemic and introduced flora

The endemic plants of St Helena include many notable "insular arborescent Asteraceae", that is, members of the sunflower family which have evolved a shrubby or tree-like habit on islands. Other notable endemics include the closely related St Helena redwood (Trochetiopsis erythroxylon) and St Helena ebony (Trochetiopsis ebenus). These are unrelated to the redwood trees of California or to the ebony trees of commerce, being instead in the Cocoa family (Sterculiaceae).

[edit] Vegetation

Today there are three major vegetation zones: the tree-fern thicket of the highest parts of the central ridge; the pastures of middle elevations and the barren, eroded "crown wastes" of lower elevations. Of these only the tree-fern thicket is a natural vegetation type. The middle elevations were formerly covered with native woodland of gumwoods (Commidendrum) and other trees, now largely destroyed. The barren "Crown wastes" were formerly covered with native scrub, of which a major component was probably St Helena ebony (Trochetiopsis ebenus and Trochetiopsis melanoxylon).

[edit] Human impact and conservation

The destruction of the native vegetation began soon after the discovery of the island by the Portuguese in 1502, with the introduction of goats. As there were no native herbivorous mammals, the flora was unadapted to such threats. Later with the establishment of permanent settlement on the island by the English East India Company in 1659, many introduced plants became established which created new vegetation types. Furthermore the native trees were subject to catastrophic cutting for such purposes as housebuilding and to fuel stills for the distillation of arrack. As a result of this legacy many endemic plant species are extinct or critically endangered.

[edit] List of endemic vascular plants of St Helena

Monocotyledons

Bulbostylis lichtensteiniana (Kunth) C.B. Clarke, Bulbostylis neglecta (Hemsl.) C.B. Clarke,

Carex dianae Steud., Carex praealta Boott,

Eragrostis saxatilis Hemsl.

Dicotyledons

Acalypha rubrinervis Cronk, Chenopodium helenense Aellen, Commidendrum robustum (Roxb.) DC. spp. robustum, Commidendrum robustum (Roxb.) DC. ssp. gummiferum (Roxb.) Cronk, Commidendrum rotundifolium (Roxb.) DC., Commidendrum rugosum (Aiton) DC., Commidendrum spurium (G. Forst.) DC., Euphorbia heleniana Thell. & Stapf, Frankenia portulacifolia (Roxb.) Spreng., Heliotropium pannifolium Burch. ex Hemsl., Hydrodea cryptantha (Hook.f.) N.E.Br., Hypertelis acida (Hook.f.) K. Müll.,

Lachanodes arborea (Roxb.) B. Nord., Melanodendron integrifolium (Roxb.) DC., Mellissia begoniifolia (Roxb.) Hook.f., Nesiota elliptica (Roxb.) Hook.f., Nesohedyotis arborea (Roxb.) Bremek., Osteospermum sanctae-helenae Norl., Pelargonium cotyledonis (L.) L'Hér., Petrobium arboreum (J.R. & G. Forst.) R. Br., Phylica polifolia (Vahl) Pillans, Pladaroxylon leucadendron ( G. Forst.) Hook.f., Plantago robusta Roxb., Sium bracteatum (Roxb.) Cronk,

Sium burchellii (Hook.f.) Hemsl., Suaeda fruticosa Forssk. ex J.F. Gmel., Trimeris scaevolifolia (Roxb.) Mabb., Trochetiopsis ebenus Cronk, Trochetiopsis erythroxylon (G. Forst.) Marais, Trochetiopsis melanoxylon (Sol. ex Sims) Marais, Trochetiopsis x benjaminii Cronk, Wahlenbergia angustifolia (Roxb.) A.DC., Wahlenbergia burchellii A.DC. in DC., Wahlenbergia linifolia (Roxb.) A.DC., Wahlenbergia roxburghii A.DC.,

Pteridophytes (Ferns and fern-allies)

Asplenium compressum Sw., Asplenium platybasis Kunze ex Mett., Ceterach haughtoni (Hook.) Cronk, Dicksonia arborescens L'Hér., Diplazium filamentosum (Roxb.) Cronk, Dryopteris cognata (C. Presl) Kuntze,

Dryopteris napoleonis (Bory) Kuntze, Elaphoglossum dimorphum (Hook. & Grev.) Moore, Elaphoglossum nervosum (Bory) H.Christ, Grammitis ebenina (Maxon) Tardieu, Hymenophyllum capillaceum Roxb., Lycopodium axillare Roxb.,

Microstaphyla furcata (L.f.) Fée, Ophioglossum polyphyllum A. Braun, Pseudophegopteris dianae (Hook.) Holttum, Pteris paleacea Roxb.

[edit] Endemic genera

Commidendrum Lachanodes Melanodendron Mellissia

Nesiota Nesohedyotis Petrobium Pladaroxylon

Trimeris Trochetiopsis

[edit] See also

• List of extinct plants. Includes several from St Helena

[edit] External links

• Plant talk article: saving the remarkable flora of St Helena
• A potted history of the flora of St Helena and its conservation

[edit] Footnotes and references

---