''Lecanora muralis'' ''(Protoparmeliopsis muralis)'' is a waxy looking, pale yellowish green

crustose Crustose is a habit of some types of algae and lichens in which the organism grows tightly appressed to a substrate, forming a biological layer. ''Crustose'' adheres very closely to the substrates at all points. ''Crustose'' is found on rocks and ...

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.rosettes radiating from a center ( placodioid) filled with disc-like yellowish-tan fruiting bodies ( apothecia).Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, , page 279 It grows all over the world.Lichen Flora of the Greater Sonoran Desert Region. Vol 2, Nash, T.H., Ryan, B.D., Gries, C., Bugartz, F., (eds.) 2001.

/ref> It is extremely variable in its characteristics as a single

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

, and may represent a complex of species. The fruiting body parts have rims of tissue similar to that of the main nonfruiting body (

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...

), which is called being

lecanorine A lichen has lecanorine fruiting body parts if they are shaped like a plate with a ring around them, and that ring is made of tissue similar to the main non-fruiting body part of the lichen.Field Guide to California Lichens, Stephen Sharnoff, Yale ...

. It is paler and greener than '' L. mellea'', and more yellow than '' L. sierrae''. In California, it may be the most common member of the ''

Lecanora ''Lecanora'' is a genus of lichen commonly called rim lichens.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, Lichens in the genus ''Squamarina'' are also called rim lichens. Members of the genus have roughly ci ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

found growing on rocks ( saxicolous).

Substrates and distribution

It grows on rock including

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular vol ...

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...

granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

, and

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

. Sometimes it can be found growing on bark. It may be tightly or loosely attached to the substrate. It grows all over the world including in Europe, Asia, North America, South America, Africa, Macaronesia,

Oceania Oceania (, , ) is a region, geographical region that includes Australasia, Melanesia, Micronesia, and Polynesia. Spanning the Eastern Hemisphere, Eastern and Western Hemisphere, Western hemispheres, Oceania is estimated to have a land area of ...

, and

Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologica ...

. In

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

, it may be the most common member of the ''

found growing on rocks ( saxicolous). In the Sonoran Desert it is found from southern

to both north and south

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

, and through

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

Sonora, Mexico Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Federal Entities of Mexico. The state is divided into 72 municipalities; the ...

, at elevation ranges from .

Description

The usually 1.5–3.5 cm (or more) wide nonvegetative body (

) is made up of parts separated by cracks (

areolate Lichens are composite organisms made up of multiple species: a fungal partner, one or more photosynthetic partners, and sometimes a basidiomycete yeast. They are regularly grouped by their external appearance – a characteristic known as their ...

) that may lift at their edges (

squamulose A squamulose lichen is a lichen that is composed of small, often overlapping "scales" called squamules. If they are raised from the substrate and appear leafy, the lichen may appear to be a foliose lichen, but the underside does not have a "skin ...

), usually growing in a neat rosette radiating from the center ( placodioid in lobes. The upper surface is pale grayish to yellow-green, being more yellow towards the lobe tips. It may be continuous to

rimose ''Rimose'' is an adjective used to describe a surface that is cracked or fissured.undulate, with their edges folded along sinuses, but never

sinuous Sinuosity, sinuosity index, or sinuosity coefficient of a continuously differentiable curve having at least one inflection point is the ratio of the curvilinear length (along the curve) and the Euclidean distance (straight line) between the ...

to plicate. Like the areolas, the edges of the lobes may be flat like planes, or raised, thickening towards tips. The ends of the lobes may be simple or

incised Incision may refer to: * Cutting, the separation of an object, into two or more portions, through the application of an acutely directed force * A type of open wound caused by a clean, sharp-edged object such as a knife, razor, or glass splinter ...

crenate A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

. The extreme tips of the lobes are in segments that are 0.3–1 mm wide. The outer edges of the lobes are darkener, sometimes being blue-green to black. The center is 0.5–2 mm (or more) thick. The

prothallus A prothallus, or prothallium, (from Latin ''pro'' = forwards and Greek ''θαλλος'' (''thallos'') = twig) is usually the gametophyte stage in the life of a fern or other pteridophyte. Occasionally the term is also used to describe the young ...

is either absent or vestigial, with areoles sometimes being contiguous and sometimes scattered. The 0.5–1 mm wide areolas may be irregular to round, with edges that are sometimes raised (squamulous), and thickened where they raise up. Coastal forms are more pale yellowish green than gray. It usually does not have a coating of fine dustlike particles (

pruinose Pruinescence , or pruinosity, is a "frosted" or dusty-looking coating on top of a surface. It may also be called a pruina (plural: ''pruinae''), from the Latin word for hoarfrost. The adjectival form is pruinose . Entomology In insects, a "blo ...

), but sometime may, especially at the margins, especially where the sinuses are folded. There are no particles are little granules of algae wrapped in fungi, for propagation ( soredia) to the point of being densely covered in chalky white material ( albopulverulenta), but soredia may be entirely lacking ( esorediate). The apothecia may be few to very crowded at the thallus center. There may be none to many that are borne at or near the margin of the areoles. The apothecia disc is rimmed with tissue that is yellowish, similar to that of the thallus. The center of the apothecia is orange to red-brown, sometimes greenish gray to black near the margins.

Cross section

The upper cortex is of the cone cortex type, with no dead algal cells, and is 50–75

µm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

(or more) thick with yellowish granules interspersed. These granules are soluble in

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

(K). The fungal filaments (

hyphae A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

) of the upper cortex are either randomly oriented to becoming

anticlinal Anticlinal may refer to: *Anticline, in structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. *Anticlinal, in stereochemistry, a torsion angle between 90° to 150°, and –90° to –150°; see Alkane_st ...

, and are 3–5 µm in diameter. Lumina are 2 µm wide. The medulla is loosely solid and cottony. The algal layer is thickened and divided into a lower surface that is white or pale to deep-yellow or brown. There may be a slight but indistinct and poorly developed lower cortex at the tips of the lobes.

Etymology

The Latin

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''muralis'' is derived from the Latin word meaning 'growing on the wall'Archibald William Smith

Species interactions

''Lecanora muralis'' is a known host to the lichenicolous fungus '' Muellerella pygmaea'' var. ''pygmaea''.Helgi Hallgrímsson & Guðríður Gyða Eyjólfsdóttir (2004)
''Íslenskt sveppatal I - smásveppir'' [Checklist of Icelandic Fungi I - Microfungi
Fjölrit Náttúrufræðistofnunar. Náttúrufræðistofnun Íslands [Icelandic Institute of Natural History]. ISSN 1027-832X

Spot tests and secondary metabolites

Lichen spot tests on the thallus in Sonoran Desert populations are usually K−, C−, KC−, and P−. Spot tests of the cortex usually are KC+ yellow to gold. Spot tests of the medulla are usually KC−. Secondary metabolites include

usnic acid Usnic acid is a naturally occurring dibenzofuran derivative found in several lichen species with the formula C18H16O7. It was first isolated by German scientist W. Knop in 1844 and first synthesized between 1933-1937 by Curd and Robertson. Usnic a ...

in the cortex, sometimes with isousnic acid. The medulla has

zeorin Zeorin is a triterpene with the molecular formula C30H52O2 which occurs in many lichens A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among hypha, filaments of multiple fungus, fungi species in a mutu ...

, and usually leucotylin and other triterpenes and fatty acids.

References

{{Taxonbar, from=Q1811239 muralis Lichen species Lichens described in 1771 Lichens of Africa Lichens of Asia Lichens of Europe Lichens of Oceania Lichens of North America Lichens of South America Lichens of Macaronesia Taxa named by Johann Christian Daniel von Schreber