St Helena olive (Nesiota elliptica)

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St Helena olive fact file

St Helena olive description

KingdomPlantae
PhylumTracheophyta
ClassMagnoliopsida
OrderRhamnales
FamilyRhamnaceae
GenusNesiota (1)

In 2002, the St Helena olive had been lost from the wild and persisted only precariously, as one cultivated individual (3), but since then this individual has died, making this species totally extinct (1). This olive was a relatively low and spreading tree with numerous branches and dark brown to black bark (2). The dark green leaves were oblong in shape with curved tips; they had a pale underside with flat-lying hairs (2). The inflorescence (flower stalk) was branched and did not rise above the leaves; in season it bore numerous, tightly packed pale pink flowers (2). The fruits were hard, woody capsules measuring one to two centimetres long, they split when mature revealing the triangular, shiny black seeds inside (2).

Size
Height: up to 4m (2)
Leaf length: 5 - 8 cm (2)
Leaf width: 2 - 3.5 cm (2)
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St Helena olive biology

Little is known about the natural ecology of the St Helena olive, but the flowering time was reported to be June to October. It is thought that pollination occured through the endemic fly Loveridgeana beattiei, and that fruits take a year to mature (2). The tree is 99 percent self-incompatible, and so could not set seed with itself or closely related individuals (4).

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St Helena olive range

Endemic to the remote island of St Helena in the southern Atlantic Ocean, this species became very rare in the 19th Century (2). It was then believed to be extinct until a single tree was found in 1977; with the death of this specimen in 1994, however, the species was lost from the wild (2). Despite tenacious attempts to cultivate cuttings from this plant, success was limited and in 2004 the St Helena olive went extinct (1).

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St Helena olive habitat

Formerly found on the highest points of the eastern central ridge (2).

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St Helena olive status

Classified as Extinct (EX) by the IUCN Red List (1).

IUCN Red List species status – Extinct

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St Helena olive threats

The remote island of St Helena was once home to a stunning array of endemic flora and fauna, which have developed there in isolation (5). Humans have exploited the island's resources for over 450 years, destroying much of the native vegetation through deforestation for timber and agriculture, and the grazing of introduced goats (5). The self-incompatibility presented serious problems for a tree confined to such a small area as the population size has been limited throughout history (4).

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St Helena olive conservation

Although seedlings have proven extremely difficult to cultivate (6), a single successful cutting was grown from the last wild tree that died in 1994. The Endemic Plant Propagation Unit at Scotland, now known as the Environmental Conservation Section, St Helena raised this cutting to a two metre tall tree, however, this was sadly lost in 1997 (7). Two seedlings from this tree were raised and planted out in the Conservation Officer’s garden at Pounceys (160 and 80 centimetres high in 1995) (3). A third seedling was planted out near to the main plant at Scotland but was later transplanted into an area on the Peaks, when the cutting died and its own growth was also severely impeded (3). A fourth seedling raised from the cutting in Scotland was planted beside the third seedling on the Peaks (3). The health of the smaller olive at Pounceys and the two on the Peaks declined and they were all dead by 1999. Only the larger seedling survived at Pounceys and, like the others, showed signs of ill health due to fungal infections (3). It finally died in 2004, leaving the species extinct (1).

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Find out more

For more information on St Helena see:

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Authentication

Authenticated (30/6/03) by Rebecca Cairns-Wicks. Chair, IUCN SSC South Atlantic Island Plant Specialist Group.

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Glossary

Endemic
A species or taxonomic group that is only found in one particular country or geographic area.
Inflorescence
The reproductive shoot of the plant, which bears flowers (See http://www.rbgkew.org.uk/ksheets/pdfs/flower.pdf for a fact sheet on flower structure).
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References

  1. IUCN Red List (September, 2008)
    http://www.iucnredlist.org
  2. Cronk, Q.C.B. (2000) The Endemic Flora of St Helena. Anthony Nelson, Shropshire.
  3. Cairns-Wicks, R. (2003) Pers. comm.
  4. Cairns-Wicks, R. (2003) Extinction of the St Helena Olive. Ascension Conservation Quarterly, 5: 6 - . Available at:
    http://www.ascensionconservation.org.ac/pdf/24-N-Quarterly-issue-no-5.pdf
  5. WWF (March, 2003)
    http://www.worldwildlife.org/wildworld/profiles/terrestrial/at/at0720_full.html
  6. Jackson, A. (1991) Project Popeye – Saving the St Helena Olive. Preliminary report to the World Wide Fund for Nature (WWF Project No. 162/89). Wakehurst Place, RBG, Kew.
  7. Joint Nature Conservation Committee (September, 2008)
    http://www.jncc.gov.uk/pdf/ot_sthelena.pdf
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Image credit

St Helena olive flowers  
St Helena olive flowers

© Rebecca Cairns-Wicks

Dr Rebecca Cairns-Wicks
PO Box 48
St Helena Island
South Atlantic Ocean
STHL 1ZZ
United Kingdom
rebecca@cwimail.sh

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