The flora of Saint Helena, an isolated island in the

South Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe an ...

, is exceptional in its high level of

endemism Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

and the severe threats facing the survival of the flora. In phytogeography, it is in the

phytochorion A phytochorion, in phytogeography, is a geographic area with a relatively uniform composition of plant species. Adjacent phytochoria do not usually have a sharp boundary, but rather a soft one, a transitional area in which many species from both r ...

St. Helena and Ascension Region of the African Subkingdom, in the

Paleotropical Kingdom The Paleotropical Kingdom (Paleotropis) is a floristic kingdom comprising tropical areas of Africa, Asia and Oceania (excluding Australia and New Zealand), as proposed by Ronald Good and Armen Takhtajan. Part of its flora, inherited from the ancient ...

Endemic and introduced flora

The endemic plants of

Saint Helena Saint Helena () is a British overseas territory located in the South Atlantic Ocean. It is a remote volcanic tropical island west of the coast of south-western Africa, and east of Rio de Janeiro in South America. It is one of three constit ...

include many notable Cabbage Tree or, "insular arborescent

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae ...

", members of the

daisy family The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

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 dwarf ebony (''

Trochetiopsis ebenus ''Trochetiopsis ebenus'', the dwarf ebony or Saint Helena ebony, is a species of flowering plant that is endemic to the island of Saint Helena in the southern Atlantic Ocean. It is not related to the ebony of commerce ('' Diospyros'' spp.), b ...

''). These are unrelated to the redwood trees of California or to the ebony trees of commerce, being instead in the Mallow family (

Malvaceae Malvaceae, or the mallows, is a family of flowering plants estimated to contain 244 genera with 4225 known species. Well-known members of economic importance include okra, cotton, cacao and durian. There are also some genera containing familia ...

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 dry, 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 ''Commidendrum'' is a genus of trees and shrubs in the family Asteraceae endemic to the island of Saint Helena in the South Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It cov ...

'') and other trees, now largely destroyed. The "Crown wastes" or coastal zones were formerly covered with native scrub, of which a major component was probably St Helena dwarf ebony (''

'' and St Helena tree ebony ''

Trochetiopsis melanoxylon ''Trochetiopsis melanoxylon'', the dwarf ebony or St Helena ebony, of the island of Saint Helena is related to ''Trochetiopsis ebenus'' but is now extinct. It differed from ''T. ebenus'' by having much smaller flowers, sepals hairless on their i ...

'').

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 The East India Company (EIC) was an English, and later British, joint-stock company founded in 1600 and dissolved in 1874. It was formed to trade in the Indian Ocean region, initially with the East Indies (the Indian subcontinent and South ...

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 Arrack is a distilled alcoholic drink typically produced in India, Sri Lanka and Southeast Asia, made from the fermented sap of coconut flowers or sugarcane, and also with grain (e.g. red rice) or fruit depending upon the country of origin ...

. As a result of this legacy many endemic plant species are extinct or critically endangered.

Endemic vascular plants of St Helena

Monocotyledons Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of ...

*''

Bulbostylis lichtensteiniana ''Bulbostylis lichtensteiniana'' is a species of flowering plant in the sedge family, Cyperaceae, that is endemic to Saint Helena. Unlike other species native to Saint Helena, such as ''Bulbostylis neglecta ''Bulbostylis neglecta'', neglec ...

'' (Kunth) C.B. Clarke *''

Bulbostylis neglecta ''Bulbostylis neglecta'', neglected tuft sedge locally, is an endemism, endemic member of the Cyperaceae of Saint Helena in the Atlantic Ocean, South Atlantic. ''Bulbostylis neglecta'' was first collected by William John Burchell in 1806, alth ...

'' (Hemsl.) C.B. Clarke *'' Carex dianae'' Steud. *'' Carex praealta'' Boott *'' Eragrostis saxatilis'' Hemsl.

Dicotyledons The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, ...

*'' Acalypha rubrinervis'' Cronk *'' Chenopodium helenense'' Aellen *''

Commidendrum robustum ''Commidendrum robustum'', the Saint Helena gumwood, is a species of tree endemic to Saint Helena, Ascension and Tristan da Cunha.Cairns-Wicks, R. 2003''Commidendrum robustum''.The IUCN Red List of Threatened Species 2003. Downloaded on 16 Sep ...

'' (Roxb.) DC. ssp. ''robustum'' *''

'' (Roxb.) DC. ssp. ''gummiferum'' (Roxb.) Cronk *''

Commidendrum rotundifolium ''Commidendrum rotundifolium'', the bastard gumwood, is a species of tree endemic to the island of Saint Helena. It was thought to be extinct, but one last tree was discovered in Horse Pasture in 1982. This tree, long believed to be the last, w ...

'' (Roxb.) DC. *''

Commidendrum rugosum ''Commidendrum rugosum'', known as scrubwood, is a species of flowering plant in the family Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within ...

'' (Aiton) DC. *''

Commidendrum spurium ''Commidendrum spurium'', the false gumwood, is a species of flowering plant in the family Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within ...

'' (G. Forst.) DC. *'' Euphorbia heleniana'' Thell. & Stapf *''

Frankenia portulacifolia ''Frankenia portulacifolia'', also called Saint Helena tea or tea plant, is a species of salt-tolerant plant in the Frankeniaceae family. It is endemic to the islands of Saint Helena, Ascension and Tristan da Cunha. Its natural habitats are inh ...

'' (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. *'' Lobelia scaevolifolia'' Roxb. *''

Melanodendron integrifolium ''Melanodendron'' is a genus of trees in the family Asteraceae, with only one species, ''Melanodendron integrifolium'' (black cabbage tree), native to the island of Saint Helena (South Atlantic Ocean). It is related to the Saint Helenan gumwood ...

'' (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 ''Pladaroxylon'' is a genus of trees in the groundsel tribe within the sunflower family.Plantago robusta'' Roxb. *'' Sium bracteatum'' (Roxb.) Cronk *'' Sium burchellii'' (Hook.f.) Hemsl. *''

Suaeda fruticosa ''Suaeda fruticosa'' is a species of flowering plant in the family Amaranthaceae (formerly placed in the family Chenopodiaceae). It is a small shrub, with very variable appearance over its wide range. It is a halophyte, and occurs in arid and sem ...

'' Forssk. ex J.F. Gmel. *''

'' Cronk *'' Trochetiopsis erythroxylon'' (G. Forst.) Marais *''

'' (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 ''Wahlenbergia roxburghii'', the Roxburgh bellflower or dwarf cabbage tree, is an extinct member of a group of four species of '' Wahlenbergia'' once known from the island of Saint Helena, in the South Atlantic Ocean. It was last seen by naturali ...

'' A.DC.

Pteridophytes A pteridophyte is a vascular plant (with xylem and phloem) that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as "cryptogams", meaning that their means of reproduction is hidden. Ferns, ...

(''Ferns'' and ''fern-allies'') *''

Asplenium compressum ''Asplenium'' is a genus of about 700 species of ferns, often treated as the only genus in the family Aspleniaceae, though other authors consider '' Hymenasplenium'' separate, based on molecular phylogenetic analysis of DNA sequences, a diffe ...

'' Sw. *''

Asplenium platybasis ''Asplenium'' is a genus of about 700 species of ferns, often treated as the only genus in the family Aspleniaceae, though other authors consider '' Hymenasplenium'' separate, based on molecular phylogenetic analysis of DNA sequences, a diffe ...

'' Kunze ex Mett. *'' Ceterach haughtoni'' (Hook.) Cronk *''

Dicksonia arborescens ''Dicksonia arborescens'', the Saint Helena tree fern, is a characteristic plant of the "tree fern thicket" vegetation of the highest parts of the central ridge of the island of Saint Helena. It is the type species of the genus ''Dicksonia''. It ...

'' 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 ''Pteris'' (brake) is a genus of about 300 species of ferns in the subfamily Pteridoideae of the family Pteridaceae. They are native to tropical and subtropical regions, southward to New Zealand, Australia, and South Africa, north to Japan ...

'' Roxb.

Endemic genera

*''

'' *'' Lachanodes'' *''

Melanodendron ''Melanodendron'' is a genus of trees in the family Asteraceae, with only one species, ''Melanodendron integrifolium'' (black cabbage tree), native to the island of Saint Helena (South Atlantic Ocean). It is related to the Saint Helenan gumwoods ...

'' *''

Mellissia ''Mellissia'' was formerly a monotypic genus in the family Solanaceae with the single species, ''Mellissia begoniifolia'' (Saint Helena boxwood), endemic to the island of Saint Helena. It was named by Joseph Dalton Hooker in honour of John Ch ...

'' *'' Nesiota''† *'' Nesohedyotis'' *''

Petrobium ''Petrobium'' is a genus in the family Asteraceae. The only known species is ''Petrobium arboreum'', called Saint Helena whitewood. It is found in the tree-fern thicket at the top of the central ridge of island of Saint Helena in the South Atlan ...

'' *'' Pladaroxylon'' *''

Trochetiopsis The flowering plant genus ''Trochetiopsis'' consists of two extant and one extinct species endemic to the island of Saint Helena (South Atlantic Ocean). They were formerly placed in the family Sterculiaceae, but this is included in the expanded M ...

References

External links

''Plant talk'' article: ''The Millennium Forest: evolving and maturing''