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Atlantic Lejeunea

Lejeunea mandonii (Steph.) Müll. Frib.

Biology

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Across its range, Atlantic lejeunea has a primarily oceanic distribution and favours areas with at least 160 wet days per year. It is found in sheltered and shady woodlands, in ravines, on north and north-east facing cliffs as well as rocky overhangs, all near to the coast.
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Conservation

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Atlantic lejeunea is listed in the UK Biodiversity Action Plans and included in English Nature's Species Recovery Programme. Plantlife, who are the lead organisation for this liverwort, hope to be able to re-introduce it to suitable former sites during the next few years. As it is also a globally scarce species, information on management and propagation of the liverwort by the Royal Botanic Gardens, Kew, will be made available to the World Conservation Monitoring Centre.
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Description

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This very small, rare plant is one of the 'leafy' liverworts, which forms thin yellow-green patches on rocks and other bryophytes.
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Habitat

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This liverwort has been found growing on other species of liverwort and moss, as well as on rocks and elderly ash, elm or oak tree trunks.
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Range

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This species is endemic to Europe, being found only in the UK, Ireland, Spain, Portugal, the Canary Islands and Madeira. Its distribution in the UK is limited to the Atlantic coastal regions and before 1970, it had been recorded from six sites, three in Cornwall and three in Scotland. However, in recent years, it has only been found at two of its Cornish sites, and its current status in Scotland is uncertain.
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Status

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Classified as Endangered in the UK.
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Threats

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The principle threats to this species are the deterioration of water quality throughout its range, through agricultural run-off and other forms of pollution, and the colonisation of much of its former habitat by encroaching rhododendron and scrub. It is intolerant of excessive shade. Rhododendron ponticum is an invasive species, which has been threatening much of our native upland habitat over the last few decades. While many people find it an attractive sight, especially when the shrub is in flower, rhododendron has the potential to devastate any habitat it colonises. The plant can spread at a rapid rate and its canopy has the ability to reach areas some considerable distance from the roots. It is also toxic to many grazing animals and insects, so it is difficult to control in any way except by laborious cutting and clearance. As well as producing dense shade, which prevents the germination of anything beneath the plant, rhododendron also grows in association with a particular fungus around its roots. This fungus effectively poisons the ground for years, even after the rhododendron itself has been removed, and any plant attempting to colonise the site will be killed. Except, of course, more rhododendron.
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Lejeunea mandonii

provided by wikipedia EN

Lejeunea mandonii, also known as Atlantic lejeunea[2] is a species of liverwort from the Lejeuneaceae family.[3]

Description

Lejeunea mandonii is a very small, leafy liverwort. Its leaves are incubous and exhibit both shades of green and yellow.[4] Stems of L. mandonii are usually less than 10mm long. [5] L. mandonii is the only British member of the genus Lejeunea that possesses smooth and cylindrical perianths. [6]

Distribution

Lejeunea mandonii is endemic to Europe where it can be found within the following countries and territories: United Kingdom, Ireland, Portugal, Canary Islands and Madeira. [4]

Within the United Kingdom it can be found in a few sites located in Western Scotland and the Lizard Peninsula of Western Cornwall. [5] The distribution within the UK is restricted to Atlantic Coastal regions. [4]

Habitat

This species can be found in sheltered and shaded woodlands where it grows among other species of liverworts and mosses. [4]

Lejeunea mandonii can also be found growing on rocky overhands, ravines and north facing cliffs near to the coast. [4]

It has also been recorded growing on the bark and trunks of trees. [4]

Threats

Lejeunea mandonii is a rare species,[5] which has populations persisting in fragmented locations.[4] Habitat fragmentation causes populations to be isolated and therefore inbreeding and a loss of genetic diversity can occur. This can cause a species to be more at risk of extinction.[7]

The species is also under threat from being shaded out by both native and introduced plant species. Heavy shade can be detrimental to L. mandonii populations.[5] Non-native evergreen tree species such as the Western Red Cedar Thuja plicata when planted in proximity to L. mandonii causes heavy shade. Deciduous tree species such as the native Sycamore Acer pseudoplatanus if allowed to mature can also be responsible for shading out L. mandonii.[5]

Invasive species such as the shrub Rhododendron ponticum can also harm L. mandonii populations. Regular human intervention is needed to cut back the shrub so that it does not shade out rocky habitat where Lejeunea mandonii grows.[5]

All three current known populations of L. mandonii in Scotland are isolated, growing on three different individual Ash trees Fraxinus excelsior.[6][5] Due to the arrival of the fungi Hymenoscyphus fraxineus within the United Kingdom, they are threatened by Ash dieback disease.[8] If these trees were to succumb to ash dieback, L. mandonii could lose further habitat.

Due to populations of L. mandonii usually being found in small patches of habitat. Its rarity and vulnerability can put it at risk of poaching by bryologists.[9]

References

  1. ^ "Lejeunea mandonii (Atlantic Pouncewort)". The IUCN Red List of Threatened Species. Retrieved 16 March 2022.
  2. ^ "Plant & Fungi Species". Plantlife. Retrieved 16 March 2022.
  3. ^ "ITIS - Report: Lejeunea mandonii". www.itis.gov. Retrieved 16 March 2022.
  4. ^ a b c d e f g "Lejeunea mandonii : Atlantic Pouncewort | NBN Atlas". species.nbnatlas.org. Retrieved 16 March 2022.
  5. ^ a b c d e f g "Atlantic lejeunea" (PDF). Plantlife.org.uk. 2022-03-19. Retrieved 2022-03-19.{{cite web}}: CS1 maint: url-status (link)
  6. ^ a b "Current status of the known populations of Lejeunea mandonii in Scotland" (PDF). www.britishbryologicalsociety.org.uk/. 2022-03-19. p. 4, 7.{{cite web}}: CS1 maint: url-status (link)
  7. ^ "What is habitat fragmentation and what does it mean for our wildlife?". woodlandtrust.org.uk. 2022-03-19. Retrieved 2022-03-19.{{cite web}}: CS1 maint: url-status (link)
  8. ^ "Ash dieback (Hymenoscyphus fraxineus)". www.forestresearch.gov.uk/. 2022-03-19. Retrieved 2022-03-19.{{cite web}}: CS1 maint: url-status (link)
  9. ^ Hallingbäck, Hodgetts, Tomas, Nick (2022-03-19). "Mosses, Liverworts and Hornworts". CiteSeerX 10.1.1.692.5228. {{cite journal}}: Cite journal requires |journal= (help)
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Lejeunea mandonii: Brief Summary

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Lejeunea mandonii, also known as Atlantic lejeunea is a species of liverwort from the Lejeuneaceae family.

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