Saturday 18 May
Fern (Ptisana purpurascens)
CRITICALLYENDANGERED
Fern fact file
- Description
- Biology
- Range
- Habitat
- Status
- Threats
- Conservation
- Find out more
- Glossary
- References
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Fern description
| Kingdom | Plantae |
| Phylum | Polypodiophyta |
| Class | Filicopsida |
| Order | Marattiales |
| Family | Marattiaceae |
| Genus | Ptisana (1) |
A large fern, Ptisana purpurascens has broad, sturdy fronds that can reach up to one metre in length (2). The dark green fronds are divided into as many as three branches, each with six pairs of leaflets, known as ‘pinnules’ (2). Ferns produce spores and these develop within structures known as ‘sori’, which line the edges of the pinnules (2).
- Synonyms
- Marattia purpurascens.
- Size
- Frond length: up to 1 m (2)
- Endemic
- A species or taxonomic group that is only found in one particular country or geographic area.
- Evergreen
- A plant which retains leaves all year round. This is in contrast to deciduous plants, which completely lose their leaves for part of the year.
- Prothallus
- A small, gamete-producing structure that germinates from certain spores.
- Spores
- Microscopic particles involved in both dispersal and reproduction. They comprise a single or group of unspecialised cells and do not contain an embryo, as do seeds.
-
IUCN Red List (August, 2012)
http://www.iucnredlist.org/ - Ashmole, P. and Ashmole, M. (2000) St. Helena and Ascension Island: a Natural History. Anthony Nelson, England.
- Gray, A. (2003) Red List Assessment Form. Ascension Conservation.
-
Australian National Herbarium (September, 2003)
http://www.anbg.gov.au/ - view the contents of, and Material on, the website;
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Fern biology
Ferns are ‘primitive’ plants that spread by releasing spores rather than by producing flowers and fruits. The distinctive frond stage of the fern lifecycle is asexual; spores are released from the fronds, which then germinate into minuscule heart-shaped structures known as ‘prothalli’. It is here that the sexual stage of the lifecycle occurs; male and female organs on the prothallus produce sperm and eggs respectively. If the female eggs are fertilised successfully, a new fern plant will begin to grow and the cycle starts again (4).
TopFern range
Ptisana purpurascens is endemic to Ascension Island in the South Atlantic, where it is now restricted to a single population on Green Mountain (3).
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Species with a similar range
Fern habitat
Ptisana purpurascens is found growing in open grassland on the exposed side of Green Mountain and amongst bamboo thickets near to the summit (3).
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Species found in a similar habitat
Fern status
Ptisana purpurascens is classified as Critically Endangered (CR) on the IUCN Red List (1).
Fern threats
The main threats to this rare fern are habitat loss due to the planting of evergreen trees and degradation due to invasive plants (1). Ptisana purpurascens is also under threat from competition with introduced species and grazing by sheep, although this is not currently a common occurrence (3).
Its highly restricted distribution makes Ptisana purpurascens particularly vulnerable to any catastrophic events. For example, a land slide could do serious damage to its main population in a single narrow ravine (1).
TopFern conservation
Ptisana purpurascens is the largest of Ascension Islands’ native plants and its population is being monitored by Ascension Conservation (3). The entire population of this species in found within Green Mountain National Park, which may offer it some protection (1).
Ptisana purpurascens is currently being grown in local nurseries and is also held at the Royal Botanic Gardens, Kew, in the United Kingdom. Small numbers of cultivated plants have been planted out, and it is hoped that this programme will be expanded in the future (1).
TopAuthentication
This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk
Glossary
References
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Image credit
Ptisana purpurascens mature plant
© Alasdair Cameron
Alasdair Cameron
http://www.themushypea.blogspot.com/
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