Chain fern (Woodwardia radicans)

Description

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Chain fern fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Chain fern description

A spectacular evergreen plant, the chain fern (Woodwardia radicans) has long, dark green, arching fronds which can grow up to two metres in length ^{(2) (4) (5)}. These oblong-shaped, pinnate leaves have a smooth, leather-like surface ⁽⁴⁾. The individual leaflets have slightly toothed edges and pointed tips ^{(4) (6)}. The chain fern grows in clumps and possesses several fronds, all with scaly buds at the tip ^{(2) (5)}.

The chain fern gains its common name from the chain-like appearance of the spore-producing structures, known as ‘sori’, on the underside of the leaf ^{(2) (4)}. 

Also known as

European chain fern.

Synonyms

Blechnum radicans .

Size

Frond length: up to 2 m ⁽²⁾

Frond width: up to 0.5 m ⁽³⁾

Chain fern biology

Each frond of the chain fern is weighed down by the bud at its tip, which can root and grow into a new plant if it touches the ground ^{(2) (4) (5)}. The chain fern also has creeping rhizomes which create new roots and shoots, enabling the plant to spread ^{(1) (5)}.

The adult fern, the sporophyte, releases spores from the ‘sori’ on the underside of the leaf, which are seen as brown spheres. The spore, when attached to a suitable substrate, develops into a gametophyte, which is tiny, green and heart-shaped. As it develops, the gametophyte grows both male and female reproductive organs. The male part of the gametophyte releases sperm, which swim towards the haploid egg. Fertilisation then occurs, fusing the egg and sperm nuclei and creating the next sporophyte generation ⁽⁹⁾.

In the chain fern, the release of spores occurs from February to September in Italy and Corsica, and during the summer months in Algeria ⁽¹⁾. 

Chain fern range

The chain fern is found in southern Europe, from Portugal east to Crete, as well as in the Azores. It also occurs in North Africa, in northern Algeria ^{(1) (2) (3) (7)}. This species is not common in any part of its range ⁽¹⁾.

Chain fern habitat

The chain fern occurs in moist, shady places in temperate regions, in areas where frost is almost absent and temperatures are mild throughout the year ^{(7) (8)}. It is commonly found in riparian woodland and woodland margins, often in acidic soil beside streams and river banks, as well as in damp ravines or caves ^{(1) (2) (7)}. In some areas the chain fern as been recorded above elevations of 400 metres ⁽³⁾. 

Chain fern status

The chain fern is classified as Endangered (EN) on the IUCN Mediterranean Red List ⁽¹⁾.

Chain fern threats

There has been a severe decline in suitable habitat for the chain fern, accelerating this species’ decrease in population size. Both the extent and quality of its habitat are declining due to forest clearance and water extraction for agricultural activities. In Corsica, the chain fern is threatened by pollution resulting from the dumping of refuse into water ⁽¹⁾.

Non-native plants from the genera Rubus and Robinia are having a detrimental effect on the chain fern due to competition for resources ⁽¹⁾. This plant occupies a very small total area and its range is severely fragmented ⁽¹⁾. 

Chain fern conservation

The chain fern is included in Annexes II and IV of the EU Habitats Directive, which protects over 1,000 plant and animal species and over 200 ‘habitat types’ of European importance ⁽¹⁰⁾. It is also listed on Appendix I of the Bern Convention, which aims to protect wild species and their habitats in Europe ⁽¹¹⁾.

More research is needed into this rare plant, including analysis of the chain fern’s genetic diversity as well as studies into its populations, habitat preferences and life cycle ^{(1) (7)}. 

Find out more

Find out more about plant conservation within the Mediterranean region:

• IUCN/SSC Mediterranean Islands Plant Specialist Group:
  http://data.iucn.org/themes/ssc/sgs/mipsg/index.htm

Discover more about the habitat of the chain fern:

• ARKive - Mediterranean Basin:
  http://www.arkive.org/eco-regions/mediterranean-basin/

Authentication

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

Chromosome

A thread of DNA protein that occurs in the nucleus of a cell.

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.

Fertilisation

The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.

Gametophyte

A stage in the life cycle of certain plants which arises from a spore and is usually haploid (its cells have only a single set of chromosomes). It produces sex cells (gametes) which go on to form a ‘sporophyte’. The gametophyte is the dominant life-cycle stage in liverworts and mosses.

Genetic diversity (genetic variation)

The variety of genes within a particular species, population or breed causing differences in morphology, physiology and behaviour.

Genus

A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.

Germinate

To begin to grow, usually following a period of dormancy and in response to favourable conditions. For example, the sprouting of a seedling from a seed.

Haploid

Term applied to the nucleus of a cell that contains one set of chromosomes (threads of DNA protein). Gametes (sex cells such as sperm and eggs) are haploid, after fertilisation the resulting organism contains a multiple of the haploid number; most organisms are diploid (contain two sets of chromosomes).

Leaflets

The individual ‘leaf-like’ parts of a compound leaf.

Pinnate

In plants, a compound leaf where the leaflets (individual ‘leaves’) are found on either side of the central stalk.

Rhizome

An underground, horizontal plant stem that produces roots and shoots.

Riparian forest

Forest that is situated along the bank of a river, stream or other body of water.

Spores

Microscopic particles produced by many non-flowering plants and fungi that are capable of developing into a new individual. Spores are adapted for dispersal and surviving for long periods of time in unfavourable conditions.

Sporophyte

The stage of a plant life cycle that produces spores (microscopic particles used in dispersal and reproduction). This stage is diploid (in the cell nucleus there are two sets of chromosomes) and is dominant in ‘higher’ plants such as flowering plants.

References

1. IUCN Mediterranean Red List (November, 2011)
   http://www.iucnredlist.org/initiatives/mediterranean
2. Phillips, R. and Rix, M. (1998) Conservatory and Indoor Plants.Volume 2. Pan Macmillan, London.
3. Sayers, D. (2006) Azores. Bradt Travel Guides, Chalfont St. Peter, England.
4. Spencer, R. (1995) Horticultural Flora of South-Eastern Australia: Ferns, Conifers and Their Allies. Volume One. University of New South Wales Press Limited, Sydney, Australia.
5. Walters, S.M. (1986) The European Garden Flora: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass Volume III: Dicotyledons.Cambridge University Press, Cambridge.
6. Brown, A.S.S. and Simmonds, M.S.J. (2006) Leaf morphology of hosts and nonhosts of the thrips Heliothrips haemorrhoidalis (Bouché). Botanical Journal of the Linnean Society, 152: 109-130.
7. Quintanilla, L.G., Pajarón, S., Pangua, E. and Amigo, J. (2000) Effect of temperature on germination in northernmost populations of Culcita macrocarpa and Woodwardia radicans. Plant Biology, 2: 612-617.
8. DeSoto, L., Quintanilla, L.G. and Méndez, M. (2008) Environmental sex determination in ferns: effects of nutrient availability and individual density in Woodwardia radicans. Journal of Ecology,96:1319-1327.
9. Yarborough, S.C. and Powell, A.M. (2002) Ferns and Fern Allies of the Trans-Pecos and Adjacent Areas. Texas Tech University Press, Texas.
10. EU Habitats Directive (November, 2011)
    http://www.jncc.gov.uk/page-1374
11. Council of Europe: Bern Convention (November, 2011)
    http://conventions.coe.int/Treaty/EN/Treaties/Html/104.htm