''Asplenium listeri'', commonly known as the Christmas Island spleenwort, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

in the family

Aspleniaceae The Aspleniaceae (spleenworts) are a family of ferns, included in the order Polypodiales. The composition and classification of the family have been subject to considerable changes. In particular, there is a narrow circumscription, Aspleniaceae ...

. It is

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 elsew ...

Christmas Island Christmas Island, officially the Territory of Christmas Island, is an Australian external territory comprising the island of the same name. It is located in the Indian Ocean, around south of Java and Sumatra and around north-west of the ...

, an

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

n territory in the northeastern

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

. Its

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

honours British zoologist and

plant collector Plant collecting is the acquisition of plant specimens for the purposes of research, cultivation, or as a hobby. Plant specimens may be kept alive, but are more commonly dried and pressed to preserve the quality of the specimen. Plant collecting i ...

Joseph Jackson Lister Joseph Jackson Lister FRS FRMS (11 January 1786 – 24 October 1869) was an amateur British opticist and physicist and the father of The 1st Baron Lister. Ancestry In 1705, Thomas Lister, a farmer and maltster, of Bingley, Yorkshire, Englan ...

, who visited the island on in 1887 and was the first to collect a specimen.

Description

The spleenwort is a small, terrestrial,

lithophytic Lithophytes are plants that grow in or on rocks. They can be classified as either epilithic (or epipetric) or endolithic; epilithic lithophytes grow on the surfaces of rocks, while endolithic lithophytes grow in the crevices of rocks (and are als ...

fern with shortly creeping rhizomes, and with fronds up to 90 mm long held in a crown.

Distribution and habitat

Found only on Christmas Island, the fern is known from a very small number of sites, where it grows in crevices on the cliffs and among the rocks of exposed

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

outcrops. It is a rare component of the sparse vegetation community characteristic of the inland cliffs which rise above the

rainforest Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...

of the terraces, and it has not been recorded from the other vegetation zones of the island. It is likely that the distribution of the species is related to sites which are well placed to capture and retain moisture from the prevailing southeasterly

trade wind The trade winds or easterlies are the permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisph ...

s.Butz (2004).

Taxonomy

The Christmas Island spleenwort is closely related to the sympatric ''

Asplenium polyodon ''Asplenium polyodon'', commonly known as sickle spleenwort, is a species of fern in the family Aspleniaceae. The distribution of ''A. polyodon'' includes parts of the countries of Australia and New Zealand. A specific locale of occurrence is in ...

'' G. Forst., known as the Sickle Spleenwort or Mare's Tails Fern. It can be distinguished from the latter by the former species’ harder and generally smaller fronds, which may be adaptations to its more exposed lithophytic habitat.

Status and conservation

It was listed as Critically Endangered on 23 July 2002 under Australia's

Environment Protection and Biodiversity Conservation Act 1999 The ''Environment Protection and Biodiversity Conservation Act 1999'' (Cth) is an Act of the Parliament of Australia that provides a framework for protection of the Australian environment, including its biodiversity and its natural and cultu ...

, when it was known only from a single location. Since then further sites have been found, but the number of known individuals of the species is less than 300, its distribution is very restricted and it is vulnerable to

stochastic Stochastic (, ) refers to the property of being well described by a random probability distribution. Although stochasticity and randomness are distinct in that the former refers to a modeling approach and the latter refers to phenomena themselv ...

disturbance events, with two of the four new locations lying outside the

Christmas Island National Park Christmas Island National Park is a national park occupying most of Christmas Island, an Australian territory in the Indian Ocean southwest of Indonesia. The park is home to many species of animal and plant life, including the eponymous Christma ...

References

Notes

Sources

* * {{Taxonbar, from=Q4808133 listeri Endemic flora of Christmas Island Ferns of Australasia Critically endangered plants Plants described in 1905 Taxa named by Carl Frederik Albert Christensen