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 else ...

and the severe threats facing the survival of the flora. In

phytogeography Phytogeography (from Greek φυτόν, ''phytón'' = "plant" and γεωγραφία, ''geographía'' = "geography" meaning also distribution) or botanical geography is the branch of biogeography that is concerned with the geographic distribution ...

, it is in the phytochorion 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 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 w ...

", members of the daisy 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 dwarf ebony ('' Trochetiopsis ebenus''). 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 familiar ...

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 co ...

'') 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 ('' Trochetiopsis ebenus'' and St Helena tree ebony '' Trochetiopsis melanoxylon'').

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 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'' (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, t ...

*'' 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 Septe ...

'' (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. Description The plant is endemic to the island of Saint Helena, off the coast of Africa. Its natural habitats are subtropical or tropical ...

'' (Aiton) DC. *''

Commidendrum spurium ''Commidendrum spurium'', the false gumwood, is a species of flowering plant in the family Asteraceae. It is found only in Saint Helena. Its natural habitats are subtropical or tropical moist lowland forests, rocky areas, and rocky shores. It ...

'' (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'' (Roxb.) DC. *'' Mellissia begoniifolia'' (Roxb.) Hook.f. *''

Nesiota elliptica The Saint Helena olive (''Nesiota elliptica'') is an extinct species of flowering plant. It is the only member of the genus ''Nesiota.'' It was endemic to the island of Saint Helena in the South Atlantic Ocean. Despite its name, it is unrelated ...

'' (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. *'' 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 ''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'' 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 ''Ophioglossum'', the adder's-tongue ferns, is a genus of about 50 species of ferns in the family Ophioglossaceae. The name ''Ophioglossum'' comes from the Greek meaning "snake-tongue".

'' A. Braun *'' Pseudophegopteris dianae'' (Hook.) Holttum *'' Pteris paleacea'' 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'' *'' Pladaroxylon'' *'' Trochetiopsis''

References

External links

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