Overview

Brief Summary

Taxonomy

Structure
A lichen is formed of two or more organisms, a fungus which forms the body of the lichen which in Xanthoria parietina consists of flattened spreading leaf-like lobes, and a green chlorococcoid alga which provides the nutrients for the fungus through photosynthesis.

Taxonomy
Xanthoria parietina belongs in the family Teloschistaceae which consist mainly of brightly coloured lichens that contain a compound that acts as both a sunscreen for the algal partner and also protects them from harmful UV rays. Hence Xanthoria is often found in sunny exposed places.
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Introduction

Watch the video to find out more about Xanthoria parietina and what lichens can tell you about pollution levels in your local environment.Xanthoria parietina, the golden shield lichen, is a conspicuous yellow foliose lichen
This lichen is formed of two organisms living together symbiotically:
  • A fungus which forms the body of the lichen, which in Xanthoria parietina consists of flattened spreading leaf-like lobes lobes and produces spores in the bright orange cups on the surface.
  • A single-celled green alga which is protected by the fungus from extreme conditions of UV or drought by the yellow colour (parietin) which acts as a sunscreen. In return the alga provides the nutrients for the fungus through photosynthesis.
Xanthoria parietina is found in sunny, exposed places that are rich in nitrogen
  • sea cliffs where seabirds provide nitrogen
  • trees, rocks and manmade substrates wherever there is plenty of nitrogen
Xanthoria parietina is tolerant of high levels of nitrogen especially ammonia and is common on trees and buildings near farmland. Xanthoria parietina can be used as a monitor for nitrogen in the atmosphere.
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Description

 Thallus: foliose, forming medium-sized to large rosettes up to 10 cm wide or sometimes colonies, rather tightly adnate, lobate; lobes: dorsiventral, concave to flattened, with a slight marginal border, 0.7-3.5 mm wide; tips: 0.5-1.5 mm wide, rotund to almost flabellate/spathulate; upper surface: yellow to orange, smooth, somewhat wrinkled, not sorediate; medulla: white, bundled, with elongate hyphae; lower surface: white (to yellow), wrinkled, with short, white hapters; Apothecia: common, laminal, stipitate, up to 8 mm in diam.; margin: smooth to crenulate; disc: orange; epihymenium: brown, c. 10 µm thick; hymenium: hyaline below, 50-90 µm tall; hypothecium: hyaline to pale brown, 15-50 µm thick; paraphyses: simple or branched, cylindrical, septate; asci: clavate, 8-spored; ascospores: ellipsoid, polarilocular, hyaline, 12-16 x 5-9 µm; septum: 3-8 µm wide; Pycnidia: common or rare, immersed, usually slightly darker than the upper surface; conidia: ellipsoid, 2.5-4 x 1-1.5 µm; Spot tests: upper surface K+ purple, C-, KC-, P-; Secondary metabolites: parietin (major), fallacinal, emodin, teloschistin and parietinic acid.; Habitat and ecology: in the Sonoran area most common on twigs (but also found on volcanic rocks), also occurring on bark, rock, as well as various other substrates (subneutral to basic, rather nutrient rich), often in humid microclimates, such as coastal regions; World distribution: circumboreal, southwards reaching into temperate regions, especially in oceanic areas, and also in subantarctic regions, Australasia, and Africa; Sonoran distribution: coastal areas of southern California and western Baja California and Baja California Sur.; Notes: Xanthoria parietina is characterized by its broad-lobed, non-sorediate thallus with frequent apothecia and ellipsoid conidia. Xanthoria elegans, which is also a comparatively large, apotheciate, and non-sorediate taxon, has narrower, convex lobes, which are tightly adnate and difficult to remove from the substrate. See also notes for that taxon. 
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Comprehensive Description

Description

 A foliose lichen forming large, rounded patches up to 10 cm across, with wide, round-lipped marginal lobes. The thallus is yellowish green to greenish grey in shade but bright orange in brightly lit situations. In older specimens the centre of the thallus may die out. Lobes are long, wrinkled, over-lapping, up to 7 mm wide at the margin, and often turn up to reveal a white underside with root-like hairs. Lobes may be narrow in exposed conditions such as on the seashore. Fruiting bodies sit on the surface of the thallus and are composed of an orange disc with a paler margin, which may become crenulate. Fruiting bodes are most abundant in the centre of the thallus.Dobson (2000) suggested that Xanthoria parietina was one of the most resistant foliose lichens to air pollution.
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Distribution

National Distribution

Canada

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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Ecology

Habitat

Depth range based on 58 specimens in 1 taxon.
Water temperature and chemistry ranges based on 16 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 11.471 - 12.348
  Nitrate (umol/L): 4.729 - 7.121
  Salinity (PPS): 35.184 - 35.363
  Oxygen (ml/l): 6.069 - 6.200
  Phosphate (umol/l): 0.336 - 0.439
  Silicate (umol/l): 2.315 - 3.285

Graphical representation

Temperature range (°C): 11.471 - 12.348

Nitrate (umol/L): 4.729 - 7.121

Salinity (PPS): 35.184 - 35.363

Oxygen (ml/l): 6.069 - 6.200

Phosphate (umol/l): 0.336 - 0.439

Silicate (umol/l): 2.315 - 3.285
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Habitat distribution

Habitat
Xanthoria parietina forms a conspicuous yellow band on sea cliffs where there are plenty of seabirds to provide the nitrogen that it loves. It is also found in other nitrogen rich habitat such as on trees and farm rooves and man-made substrates inland where the atmospheric nitrogen levels are high.Xanthoria parietina is found in nitrogen rich habitats .

Distribution
Xanthoria is widespread over Britain, Europe and America but in tropical countries and in Australia it is rather rare. Its association with nitrogen and agricultural dust means that it has spread rapidly where man has cultivated the land and introduced stock, and since the clean-air acts it is now frequent in our cities.

Ecology
Xanthoria parietina occurs with other lichen species in a distinctive lichen community which is named after it…the Xanthorion, and includes other species which are tolerant of nitrogen such as the grey-green Physcia.
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 Xanthoria parietina may form a distinct narrow band on rocks and walls just above high water level. It also occurs inland on rocks, walls and bark. Common on nutrient rich areas such as beneath bird perching areas.
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Associations

In Great Britain and/or Ireland:
Lichen / parasite
ascoma of Arthonia epiphyscia parasitises thallus of Xanthoria parietina

Lichen / gall
perithecium of Endococcus parietinarius causes galls on thallus of Xanthoria parietina

Lichen / parasite
pycnidium of Lichenoconium coelomycetous anamorph of Lichenoconium xanthoriae parasitises blackened apothecium of Xanthoria parietina

Lichen / parasite
sporodochium of Marchandiomyces anamorph of Marchandiomyces corallinus parasitises bleached thallus of Xanthoria parietina

Lichen / parasite
lirella of Opegrapha parasitica parasitises Xanthoria parietina

Lichen / gall
perithecium of Telogalla olivieri causes galls on thallus of Xanthoria parietina

Lichen / pathogen
colony of Xanthoriicola dematiaceous anamorph of Xanthoriicola physciae infects and damages blackened thallus of Xanthoria parietina
Other: minor host/prey

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Life History and Behavior

Reproduction

Only the fungal partner reproduces sexually from spores that are produced in the golden disc-like fruits on the surface. When the spores germinate they have to associate with a green algal partner in order to develop into the characteristic lichen. The green algal partner is rarely found free-living so it appears that Xanthoria may obtain its essential algal partner from other lichens.
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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: NNR - Unranked

United States

Rounded National Status Rank: NNR - Unranked

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NatureServe Conservation Status

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: This lichen species occurs west of the Cascades and is known only from the Williamette-Puget trough in the Pacific Northwest. It also occurs in eastern North America and Europe near the coast (McCune and Geiser 1997).

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Wikipedia

Xanthoria parietina

Xanthoria parietina is a foliose, or leafy, lichen. It has wide distribution, and many common names such as common orange lichen, yellow scale, maritime sunburst lichen and shore lichen. It can be found near the shore on rocks or walls (hence the epithet parietina meaning "on walls"), and also on inland rocks, walls, or tree bark. It was chosen as a model organism for genomic sequencing (planned in 2006) by the US Department of Energy Joint Genome Institute (JGI). In the past it was used as a remedy for jaundice because of its yellow color.

X. parietina growing on brick...
..on a branch of Cornus mas during spring time..
... and on a dead branch.

Taxonomy[edit]

The species was first described by Carl Linnaeus in 1753, as Lichen parietinus.

Description[edit]

The vegetative body of the lichen, the thallus, is foliose, and typically less than 8 centimetres (3.1 in) wide. The lobes of the thallus are 1–4 mm in diameter, and flattened down. The upper surface is some shade of yellow, orange, or greenish yellow, while the lower surface is white, with a cortex, and with sparse pale rhizines or hapters. The vegetative reproductive structures soredia and isidia are absent in this species, however, apothecia are usually present.[1]

The outer "skin" of the lichen, the cortex, is composed of closely packed fungal hyphae and serves to protect the thallus from water loss due to evaporation as well as harmful effects of high levels of irradiation. In Xanthoria parietina, the thickness of the thalli is known to vary depending on the habitat is which it grows. Thalli are much thinner in shady locations than in those exposed to full sunshine; this has the effect of protecting the algae that cannot tolerate high light intensities. The lichen pigment parietin gives this species a deep yellow or orange-red color.[2]

X. parietina prefers growing on bark and wood; it is found more rarely on rock.[1] Nutrient enrichment by bird droppings enhances the ability of X. parietinato grow on rock.[3]

Photobiont[edit]

The photosynthetic symbionts, or photobionts, associated with X. parietina are from the green algal genus Trebouxia. Species that have been found include Trebouxia arboricola and T. irregularis.[4] Both of these photobionts are known to occur free-living in nature, having been found on bark colonized by X. parietina as well as on bark not colonized by lichens.[5]

In one study, the photobiont was shown to occupy 7% of the volume of the thallus.[6] The density of pigmentation of the upper cortex also varies and seems to control the amount of light reaching the algae.[6]

Reproduction and dispersal[edit]

A large number of lichens disperse very effectively by means of symbiotic vegetative propagules such as soredia, isidia and blastidia, and thallus fragmentation. However, X. parietina does not produce the vegetative propagules, but has to establish the symbiotic state at each reproductive cycle. It has been demonstrated that two orbatid mite species, Trhypochtonius tectorum, and Trichoribates trimaculatus, common inhabitant and consumers of X. parietina, are vectors of the photobiont cells. Faecal pellets of both species contain both viable ascospores and photobiont cells, and are suggested to be a common mode of vegetative short- and long-distance dispersal of this species.[7]

Habitat and distribution[edit]

Hardwood forests in low-elevation broad valleys; scattered on Populus and other hardwoods in riparian areas in agricultural and populated areas.[1] It is often associated with high level of nitrogen and favored by eutrophication [8][9] and can be often found near farmland and around livestock.[10]

X. parietina is a widespread lichen, and has been reported from Australia, Africa, Asia, North America[11] and throughout much of Europe.[12] In eastern North America and Europe, it is found more frequently near coastal locations.[1] The increases in nitrate deposition as a result of industrial and agricultural developments in southern Ontario, Canada in the 20th century are thought to be responsible for the reappearance of this species in the local lichen flora.[13]

Pollution tolerance[edit]

Xanthoria parietina is a very pollution-tolerant species. In laboratory experiments, this species can tolerate exposure to air contaminants and bisulphite ions with little or no damaging effect.[14] It is also tolerant of heavy metal contamination.[15]

For these reasons, this species has found use as a biomonitor for measuring levels of toxic elements.[16][17]

Bioactive compounds[edit]

Structure of parietin, orange-colored pigment found in X. parietina.

X. parietina produces an orange colored anthraquinone pigment, parietin, that gets deposited as tiny crystals in the top layer of the upper cortex. Parietin synthesis is enhanced by UV-B,[18] and stimulated by photosynthates, such as those provided by the green algal Trebouxia symbiont.[19] X. parietina also produces the metabolite 2-methoxy-4,5,7-trihydroxy-anthraquinone.[20]

Medicinal properties[edit]

The water extract of X. parietina has good antiviral activity in vitro, inhibiting the replication of human parainfluenza virus type 2.[21]

Gallery[edit]

References[edit]

  1. ^ a b c d Geiser, Linda; McCune, Bruce (1997). Macrolichens of the Pacific Northwest. Corvallis: Oregon State University Press. p. 321. ISBN 0-87071-394-9. 
  2. ^ Galun, Margalith (1988). CRC Handbook of Lichenology, Volume I. Boca Raton: CRC. p. 105. ISBN 0-8493-3581-7. 
  3. ^ Armstrong RQ. (1984). "The influence of bird droppings and uric acid on the growth of five species of saxicolous lichens." Environmental and Experimental Botany 24: 95.
  4. ^ Ahmadjian, Vernon. (1993). The lichen symbiosis. New York: John Wiley. pp. 32–33. ISBN 0-471-57885-1. 
  5. ^ Bubrick P, Galun M, Frensdorff A. (1984). "Observations on free-livingTrebouxia de Puymaly and Pseudotrebouxia Archibald, and evidence that both symbionts from Xanthoria parietina (L.) Th. Fr. can be found free-living in nature." New Phytologist 97: 455.
  6. ^ a b Biology of Lichens. Cambridge, UK: Cambridge University Press. 1983. p. 51. ISBN 0-7131-2457-1. 
  7. ^ Meier FA, Scherrer S, Honegger R. (2002). "Faecal pellets of lichenivorous mites contain viable cells of the lichen-forming ascomycete Xanthoria parietina and its green algal photobiont, Trebouxia arbicola." Biological Journal of the Linnean Society76(2): 259–268.
  8. ^ Gaio-Oliveira G, Dahlman L, Palmqvist K, Máguas C. (2004). "Ammonium uptake in the nitrophytic lichen Xanthoria parietina and its effects on vitality and balance between symbionts."Lichenologist 36: 75–86.
  9. ^ Van Herk CM. (1999). "Mapping of ammonia pollution with epiphytic lichens in The Netherlands." Lichenologist 31:9–20.
  10. ^ Frati L, Santoni S, Nicolardi V, Gaggi C, Brunialti G, Guttova A, Gaudino S, Pati A, Pirintsos SA, Loppi S. (2007). Lichen biomonitoring of ammonia emission and nitrogen deposition around a pig stockfarm. Environmental Pollution 146: 311&ndsash;6.
  11. ^ Hogan, C. Michael. 2008. Black Spruce: Picea mariana, GlobalTwitcher.com, ed. Nicklas Stromberg
  12. ^ Lindblom L. (1997). "The genus Xanthoria (Fr.) Th. Fr. in North America." Journal of the Hattori Botanical Laboratory 83:75–172.
  13. ^ Brodo IM, Lewis C, Craig B. (2007). "Xanthoria parietina, a coastal lichen, rediscovered in Ontario." Northeastern Naturalist 14(2): 300–6.
  14. ^ Silberstein L, Siegel BZ, Sigel SM, Mukhtar A, Galun M. (1996). Comparative studies on Xanthoria parietina, a pollution-resistant lichen and Ramalina duriaei, a sensitive species. I. Effects of air pollution of physiologocal processes." Lichenologist 28(4): 355–65.
  15. ^ Bačkor M, Fahselt D, Davidson R, Wu CT. (2003). "Effects of copper on wild and tolerant strains of the lichen photobiont Trebouxia erici (Chlorophyta) and possible tolerance mechanisms." Archives of Environmental Contamination and Toxicology 45: 159–67.
  16. ^ Brunialti G, Frati L. (2007). Biomonitoring of nine elements by the lichen Xanthoria parietina in Adriatic Italy: A retrospective study over a 7-year time span.Science of the Total Environment 387(1–3): 289-300.
  17. ^ Loppi S, Paoli L, Gaggi C. 2006). "Diversity of epiphytic lichens and Hg contents of Xanthoria parietina Thalli as monitors of geothermal air pollution in the Mt. Amiata area (Central Italy)."Journal of Atmospheric Chemistry 53(2): 93–105.
  18. ^ Solhaug KA, Gauslaa Y, Nybakken L, Bilger W. (2003). "UV-induction of sun-screening pigments in lichens." New Phytologist 158:91–100.
  19. ^ Solhaug KA, Gauslaa Y. (2004). "Photosynthates stimulate the UV-B induced fungal anthraquinone synthesis in the foliose lichen Xanthoria parietina." Plant Cell and Environment 27: 167–76.
  20. ^ Ivanova V, Schlegel R, Gräfe U (October 2000). "2-Methoxy-4,5,7-trihydroxy-anthraquinone, a new lichen metabolite produced by Xanthoria parietina". Pharmazie 55 (10): 785–6. PMID 11082848. 
  21. ^ Karagoz A, Aslan A. (2005). Antiviral and cytotoxic activity of some lichen extracts. Biologia 60(3): 281–6.
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