Asplenium listeri
Encyclopedia
Asplenium listeri, commonly known as the Christmas Island Spleenwort, is a species
of fern
in the Aspleniaceae
family. It is endemic to Christmas Island
, an Australia
n territory in the north-eastern Indian Ocean
. Its specific epithet honours British zoologist and plant collector
Joseph Jackson Lister
, who visited the island on HMS
Egeria in 1887 and was the first to collect a specimen.
fern with shortly creeping rhizomes, and with fronds up to 90 mm long held in a crown.
outcrops. It is a rare component of the sparse vegetation community characteristic of the inland cliffs which rise above the rainforest
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 south-easterly trade wind
s.
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.
on 23 July 2002 under Australia’s Environment Protection and Biodiversity Conservation Act 1999
, 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
disturbance events, with two of the four new locations lying outside the Christmas Island National Park
.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
in the Aspleniaceae
Aspleniaceae
The Aspleniaceae is a family of ferns, included in the order Polypodiales or in some classifications as the only family in the order Aspleniales....
family. It is endemic to Christmas Island
Christmas Island
The Territory of Christmas Island is a territory of Australia in the Indian Ocean. It is located northwest of the Western Australian city of Perth, south of the Indonesian capital, Jakarta, and ENE of the Cocos Islands....
, an Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
n territory in the north-eastern Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
. Its specific epithet honours British zoologist and plant collector
Plant collecting
Plant collecting involves procuring live or dried plant specimens, for the purposes of research, cultivation or as a hobby.-Collection of live specimens:...
Joseph Jackson Lister
Joseph Jackson Lister (naturalist)
Joseph Jackson Lister FRS was a British zoologist and plant collector from Leytonstone who collected biological specimens during travels in Africa, Asia, Australasia and the Pacific region....
, who visited the island on HMS
Her Majesty's Ship
Her or His Majesty's Ship is the ship prefix used for ships of the navy in some monarchies, either formally or informally.-HMS:* In the British Royal Navy, it refers to the king or queen of the United Kingdom as appropriate at the time...
Egeria in 1887 and was the first to collect a specimen.
Description
The spleenwort is a small, terrestrial, lithophyticLithophyte
Lithophytes are a type of plant that grows in or on rocks. Lithophytes feed off moss, nutrients in rain water, litter, and even their own dead tissue....
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 limestoneLimestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
outcrops. It is a rare component of the sparse vegetation community characteristic of the inland cliffs which rise above the rainforest
Rainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
of the terraces
Marine terrace
A marine terrace, coastal terrace, raised beach or perched coastline is a relatively flat, horizontal or gently inclined surface of marine origin, mostly an old abrasion platform which has been lifted out of the sphere of wave activity . Thus it lies above or under the current sea level, depending...
, 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 south-easterly trade wind
Trade wind
The trade winds are the prevailing pattern of easterly surface winds found in the tropics, within the lower portion of the Earth's atmosphere, in the lower section of the troposphere near the Earth's equator...
s.
Taxonomy
The Christmas Island Spleenwort is closely related to the sympatric Asplenium polyodonAsplenium 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...
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 EndangeredCritically Endangered
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....
on 23 July 2002 under Australia’s Environment Protection and Biodiversity Conservation Act 1999
Environment Protection and Biodiversity Conservation Act 1999
The Environment Protection and Biodiversity Conservation Act 1999 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 culturally significant places...
, 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
Stochastic refers to systems whose behaviour is intrinsically non-deterministic. A stochastic process is one whose behavior is non-deterministic, in that a system's subsequent state is determined both by the process's predictable actions and by a random element. However, according to M. Kac and E...
disturbance events, with two of the four new locations lying outside the Christmas Island National Park
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 red crab, whose annual migration sees around 100 million...
.