The Saint Helena olive (''Nesiota elliptica'') is an extinct species of
flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
. It is the only member of the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
''Nesiota.'' It was
endemic
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 ...
to the island of
Saint Helena in the South Atlantic Ocean. Despite its name, it is unrelated to the true
olive (''
Olea europaea''), but is instead a member of the family
Rhamnaceae, the family which contains
buckthorns and
jujube
Jujube (), sometimes jujuba, known by the scientific name ''Ziziphus jujuba'' and also called red date, Chinese date, and Chinese jujube, is a species in the genus '' Ziziphus'' in the buckthorn family Rhamnaceae.
Description
It is a smal ...
. The last remaining tree in the wild died in 1994, and the last remaining individual in cultivation died in December 2003, despite conservation efforts. It is thus a prime example of recent plant
extinction
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
. The Saint Helena olive belongs to the tribe Phyliceae, which are mostly endemic to Southern Africa.
Description
The Saint Helena Olive was native to the
cloud forest found in the upland areas of the island above 750 metres, with many historical records around
Diana's Peak (the highest point on the island). It grew as a small, low growing spreading tree with prolific branching. The bark was dark brown to black. The leaves were oblong in shape and dark green, with downward curving tips. The undersides of the leaves were pale with hairs that lay flat along the leaf. During the flowering season, which is presumed to have run from June to October, the tree bore tightly packed pink flowers on branched
inflorescence
An inflorescence is a group or cluster of flowers arranged on a Plant stem, stem that is composed of a main branch or a complicated arrangement of branches. Morphology (biology), Morphologically, it is the modified part of the shoot of sperma ...
s. The flowers are presumed to have been pollinated by the local endemic
hoverfly
Hover flies, also called flower flies or syrphid flies, make up the insect family Syrphidae. As their common name suggests, they are often seen hovering or nectaring at flowers; the adults of many species feed mainly on nectar and pollen, whil ...
species ''
Sphaerophoria beattiei.'' The fruit took a year to mature, and consisted of a hard woody capsule containing shiny triangular black seeds.
Extinction
The Saint Helena olive was already rare by the 19th century due to deforestation and grazing by introduced goats, and was previously thought to be extinct until a single living specimen was discovered in 1977. It was highly
self-incompatible
Self-incompatibility (SI) is a general name for several genetic mechanisms that prevent self-fertilization in sexually reproducing organisms, and thus encourage outcrossing and allogamy. It is contrasted with separation of sexes among individuals ...
, meaning that most seeds produced with itself or close relatives would fail, making it extremely difficult to grow seedlings, given that the population size for the plant had probably always been low. Despite immense effort, only a single cutting of the plant was able to be cultivated, with a handful of seedlings grown from it. The original wild plant died in 1994, making the species extinct in the wild. The final known specimen in cultivation, a seedling of the cutting, which had been the only surviving plant since 1999, died in 2003 from fungus and termite infestation, making the species totally extinct.
A sample of DNA from the Saint Helena Olive is stored at Kew Gardens DNA bank. The Saint Helena Olive is one of a number of plant species to have gone extinct on Saint Helena since the arrival of the Portuguese in 1502, including ''
Trochetiopsis melanoxylon,
Acalypha rubrinervis,
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 ...
,'' and ''
Heliotropium pannifolium,'' with ''
Lachanodes arborea'' and ''
Trochetiopsis erythroxylon'' also
extinct in the wild.
Phylogenetics
The Saint Helena olive is part of the
tribe
The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English is in the discipline of anthropology. This definition is contested, in part due to confli ...
Phyliceae within
Rhamnaceae. The Phyliceae are mostly endemic to Southern Africa, particularly the
Fynbos region of South Africa.
Relationships of Phyliceae, after
See also
*
Flora of St Helena
References
*
Cronk, Q.C.B. (1995) The endemic Flora of St Helena. Anthony Nelson Ltd., Oswestry.
{{Taxonbar, from1=Q374064, from2=Q13108102
Rhamnaceae
Flora of Saint Helena
Extinct plants
Extinct biota of Africa
Plant extinctions since 1500