Crustose lichen

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Crustose lichens on a wall N2 Lichen.jpg
Crustose lichens on a wall
Growth of crustose lichen on a tree trunk Crustose lichen.jpg
Growth of crustose lichen on a tree trunk

Crustose lichens are lichens that form a crust which strongly adheres to the substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. [1] The basic structure of crustose lichens consists of a cortex layer, an algal layer, and a medulla. The upper cortex layer is differentiated and is usually pigmented. The algal layer lies beneath the cortex. The medulla fastens the lichen to the substrate and is made up of fungal hyphae. [2] The surface of crustose lichens is characterized by branching cracks that periodically close in response to climatic variations such as alternate wetting and drying regimes. [3]

Contents

Subtypes

The thallus appears powdery. [1]
E.g. Genera Lepraria , Vezdaea
upper cortex is usually developed. [1]
E.g. Genus Lecidea
E.g. Acarospora fuscata
E.g. Lecania naegelii
E.g. Amandinea punctata
It is an intermediate form between crustose and foliose. [1]
E.g. Genus Psora, Catapyrenium, Coriscium
E.g. Peltula euploca
E.g. Genus Mobergia
E.g. Genera Acarospora, Pleopsidium
E.g. Genera Caloplaca, Lecanora
E.g. Peltula clavata

Structure

Crustose lichen forms a thin crust adhering closely to the substratum. In some cases, this crust may be thick and lumpy, and may be detached, in part, or submerged below its surface. The thallus of a crustose lichen is usually only discernible because of the discolouration of the substrate. Some crustose lichens have thalli consisting of scattered or loosely grouped granules. Crustose lichens differ from the leprose lichen by having an upper cortex and algal cells that are located directly beneath the cortex. The thallus of a crustose lichen has a patchwork or crazy-paving appearance. The patches, or areolae, can be as large as 1 cm in diameter or very small and raised, giving them the appearance of a wart. The surface of the thallus is generally smooth, however it is sometimes broken up by “rimose” cracks. These cracks are a by-product of thallus surface shrinkage, which is caused by alternate wetting and drying. An underlayer of fungal hyphae, the hypothallus, is present on some species of crustose lichens. A dark rim on the areolae may form in areas where the hypothallus is exposed. This may also be present on the thallus itself. These fungal hyphae are usually what attach the thallus firmly to the substrate. [5]

Growth

In general, lichens do not grow very quickly. Annual growth rates vary among different growth forms. Crustose lichens have the lowest rates of growth. [6]

The diameter and area of the thallus exponentially increase, provided that organic substances are distributed uniformly in all parts of the lichens. However, as the thallus increases in size, the circumference also increases, which corresponds to a larger increase in volume. As a result, movement and uniform distribution of organic substances become more difficult. [7]

Growth factors

The growth of crustose lichens is dependent on several factors, including moisture levels, sunlight, and temperature. High rates of precipitation and high moisture levels promote the growth of crustose lichens. Crustose lichens are more prevalent in areas with higher precipitation. [8] A similar trend is observed when aridity is taken into account. Crustose lichens prefer sites of lower aridity. [9]

Sunlight

The amount of sunlight that lichens receive determines the rate at which photosynthesis occurs. [10] Moreover, surface area also influences photosynthetic rates. In high sunlight conditions, foliose lichens with broad lobes are prevalent. [8] In comparison, crustose lichens have less surface area than foliose lichens and will tend to have slower photosynthetic rates. Generally, higher levels of sunlight promote growth of the crustose lichens.

Temperature

Extreme temperatures are unfavorable for the growth of crustose lichens. Temperatures below 0 °C can result in cessation of growth and thalli freezing. [10] Annual growth rates for the Rhizocarpon subgenus show a correlation with annual and winter mean temperatures, but not with mean summer temperatures. [11]

Unfortunately, little faith can be put in these correlations because they use unvalidated measures of unknown accuracy and precision and measurement of growth was done along a single diameter. Since thallus growth along any radius might not match growth along any other radius it is unclear if these correlations are meaningful. Various publications can be consulted to see that there is tremendous within thallus variation in lateral growth (e.g., [12] ).

The scientific basis of lichenometric dating and the reliability of lichen growth rate measurements in general have been questioned and critically reviewed in a paper by Osborn et al. (2015). [13] Those criticisms of lichenometric dating have yet to be answered.

Photosynthesis

Photosynthetic rates vary among lichen growth forms due to differences and variations in thalli thicknesses. Irregular thicknesses in crustose lichens result in greater variation in photosynthetic rates relative to more uniformly thick forms such as foliose lichens. [6]

Distribution and habitat

Crustose lichens can be found in a wide range of areas. They can be found, among others, together with epiphytic algae and liverworts, living on the surfaces of leaves of tropical evergreen trees and shrubs. [14] They also thrive in carbonate-rich karst areas. In southern China, it has been estimated that 5-30% of rock outcrops in bare karst areas and 30-70% in forest karst areas are covered with crustose lichens. [15] Crustose lichens also flourish in extreme environments. Various species of crustose lichens, including Biatora granulosa and Lecidea uliginosa, were found covering recently-burned surfaces caused by a subarctic forest fire in an area near the Great Slave Lake. [16] Crustose lichens also grow in areas of high elevations, such as the western Himalayan region. Concentrations of terricolous crustose lichens were highest in areas of higher elevation, relative to other foliose and fruticose lichens. [17] In areas of high pollution, the majority of lichens are killed and are the first plants to disappear in cities due to their high sensitivity to atmospheric pollutants. Nonetheless, surrounding the central area of cities in which most plants cannot thrive, crustose lichens Physcia or Xanthoria have been found growing, although they do fall short of natural development and size. The crustose lichen Lecanora conizaeoides is another highly resilient species, and remarkably seems to only grow in industrial areas of the United Kingdom. [18]

Significance

Saxicolous crustose lichens play an important role in the weathering of rocks. Repeated contraction and expansion of thalli occurs in response to alternate periods of wetting and drying, resulting in the breakdown of rock fragments and removal of mineral grains from the rock surfaces. [18] Crustose lichens also chemically weather rocks through hydrolysis. In a study conducted by Kitagawa and Watanabe (2004), the crustose genus Porpidia altered minerals, specifically biotite in granite. Furthermore, vermiculite-like minerals were formed as a result of biotite alteration through hydrolysis. [19] Crustose lichens living in karst areas have substantial influence on carbon dioxide flux at the boundary between the lithosphere and atmosphere because they increase the rates of corrosion of carbonate rocks in these areas. [15] Some species of crustose lichens exhibit antibiotic properties. Lepraria chlorina contains substantial amounts of vulpinic acid, which is a chemical that has anti-inflammatory properties. [20] Crustose lichens may also be used for dating rock surfaces, through a technique called lichenometry. As soon as a rock is exposed to the Earth’s atmosphere, spores of various organisms are driven into the crevices on the surface. The majority of these spores die under the extreme conditions of a rock surface, an area where water evaporates rapidly and daily fluxes in temperatures are quite large. The spores of some crustose lichens, however, can develop on these surfaces. Eventually the crustose spores form small and round thalli and increase in diameter yearly. When lichens are used for dating a rock surface, only the diameters of the largest thalli of one species are measured, as there is an assumption that only they began development when the surface was initially exposed. The age of exposure of a rock surface is then extrapolated from records. [7]

Related Research Articles

<span class="mw-page-title-main">Lichen</span> Symbiosis of fungi with algae or cyanobacteria

A lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. Lichens are important actors in nutrient cycling and act as producers which many higher trophic feeders feed on, such as reindeer, gastropods, nematodes, mites, and springtails. Lichens have properties different from those of their component organisms. They come in many colors, sizes, and forms and are sometimes plant-like, but are not plants. They may have tiny, leafless branches (fruticose); flat leaf-like structures (foliose); grow crust-like, adhering tightly to a surface (substrate) like a thick coat of paint (crustose); have a powder-like appearance (leprose); or other growth forms.

<span class="mw-page-title-main">Verrucariaceae</span> Family of mostly lichenised fungi

Verrucariaceae is a family of lichens and a few non-lichenised fungi in the order Verrucariales. The lichens have a wide variety of thallus forms, from crustose (crust-like) to foliose (bushy) and squamulose (scaly). Most of them grow on land, some in freshwater and a few in the sea. Many are free-living but there are some species that are parasites on other lichens, while one marine species always lives together with a leafy green alga.

<i>Acarospora</i> Genus of fungi

Acarospora is a genus of mostly lichen-forming fungi in the family Acarosporaceae. Most species in the genus are crustose lichens that grow on rocks in open and arid places all over the world. They may look like a cobblestone road or cracked up old paint, and are commonly called cobblestone lichens or cracked lichens. They usually grow on rock, but some grow on soil (terricolous) or on other lichens. Some species in the genus are fungi that live as parasites on other lichens. Acarospora is a widely distributed genus, with about 128 species according to a 2008 estimate.

Acarospora flavisparsa is a species of lichen in the family Acarosporaceae. Found in Portugal and Spain, it was described as new to science in 2011. The lichen grows on acidic rock walls in inland areas.

Lichens of the Sierra Nevada have been little studied. A lichen is a composite organism consisting of a fungus and a photosynthetic partner growing together in a symbiotic relationship.

<span class="mw-page-title-main">Fruticose lichen</span> Form of lichen

A fruticose lichen is a form of lichen fungi that is characterized by a coral-like shrubby or bushy growth structure. It is formed from a symbiotic relationship of a photobiont such as green algae or less commonly cyanobacteria and one, two or more mycobionts. Fruticose lichens are not a monophyletic and holophyletic lineage, but is a form encountered in many classes. Fruticose lichens have a complex vegetation structure, and are characterized by an ascending, bushy or pendulous appearance. As with other lichens, many fruticose lichens can endure high degrees of desiccation. They grow slowly and often occur in habitats such as on tree barks, on rock surfaces and on soils in the Arctic and mountain regions.

<span class="mw-page-title-main">Lichen growth forms</span> Gross morphological classification

Lichens are symbiotic organisms made up of multiple species: a fungus, one or more photobionts and sometimes a yeast. They are regularly grouped by their external appearance – a characteristic known as their growth form. This form, which is based on the appearance of vegetative part of the lichen, varies depending on the species and the environmental conditions it faces. Those who study lichens (lichenologists) have described a dozen of these forms: areolate, byssoid, calicioid, cladoniform, crustose, filamentous, foliose, fruticose, gelatinous, leprose, placoidioid and squamulose. Traditionally, crustose (flat), foliose (leafy) and fruticose (shrubby) are considered to be the three main forms. In addition to these more formalised, traditional growth types, there are a handful of informal types named for their resemblance to the lichens of specific genera. These include alectorioid, catapyrenioid, cetrarioid, hypogymnioid, parmelioid and usneoid.

<span class="mw-page-title-main">Lichen morphology</span>

Lichen morphology describes the external appearance and structures of a lichen. These can vary considerably from species to species. Lichen growth forms are used to group lichens by "vegetative" thallus types, and forms of "non-vegetative" reproductive parts. Some lichen thalli have the aspect of leaves ; others cover the substrate like a crust, others such as the genus Ramalina adopt shrubby forms, and there are gelatinous lichens such as the genus Collema.

<i>Acarospora socialis</i> Species of lichen

Acarospora socialis is a usually bright yellow areolate to squamulose crustose lichen in the family Acarosporaceae that grows up to 10 cm wide, mostly on rock in western North America. It is among the most common lichens in the deserts of Arizona and southern California. It grows on sandstone, intrusive and extrusive igneous rock such as granitics, in all kinds of exposures to sunlight, including vertical rock walls. It is found in North America, including areas of the Mojave Desert and Sonoran Desert region, to Baja California Sur. It is the most common yellow member of its genus in southwestern North America. It sometimes, but rarely, grows on other soil crusts. It is a pioneer species.

<i>Lecanora muralis</i> Species of lichen

Lecanora muralis(Protoparmeliopsis muralis) is a waxy looking, pale yellowish green crustose lichen that usually grows in rosettes radiating from a center (placodioid) filled with disc-like yellowish-tan fruiting bodies (apothecia). It grows all over the world. It is extremely variable in its characteristics as a single taxon, and may represent a complex of species. The fruiting body parts have rims of tissue similar to that of the main nonfruiting body (thallus), which is called being lecanorine. 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 genus found growing on rocks (saxicolous).

<i>Acarospora thamnina</i> Species of fungus

Acarospora thamnina is a shiny, black tinged, variously brown squamulose crustose lichen. It has a linear growth pattern, growing along cracks in boulders. It can be found in North America to Alaska and Maine, from the coast to inland locations, also in the Ural Mountains and Novaya Zemlya in Russia. It commonly grows either among, or on other lichens. It grows a longer stipe so its squamules can grow over other lichens when there is competition for space. When it forms thick clumps it is easily identified with its elevated squamules and thick stipes. It grows on acidic rock in full sunlight.

<i>Pleopsidium chlorophanum</i> Species of lichen-forming fungus

Pleopsidium chlorophanum is a distinctively colored, bright lemon-yellow to chartreuse crustose lichen, which favors dry arctic or alpine sandstone cliffs and boulders. It is a rare alpine lichen in Europe. It is in the genus Pleopsidium of the family Acarosporaceae.

<i>Carbonicola</i> (lichen) Genus of lichens

Carbonicola is a small genus of lichen-forming fungi. It is the sole genus in the monogeneric family Carbonicolaceae. The genus, which collectively has an almost cosmopolitan distribution, contains three squamulose lichens that prefer to grow on burned wood in temperate areas of the world.

Acarospora pseudofuscata is a species of saxicolous (rock-dwelling) crustose lichen in the family Acarosporaceae. It occurs on a few islands in the Aegean Sea and in Turkey.

Lecidea hoganii is a rare species of saxicolous (rock-dwelling), crustose lichen in the family Lecideaceae. It is known to occur only in Boulder, Colorado, where it grows in association with other lichens in mixed saxicolous communities on sandstone in the Fox Hills Formation. The lichen is characterized by its thick white, chalky thallus, sessile to raised apothecia, presence of a dark pink pigment in the hymenium, and absence of secondary compounds.

<i>Buellia frigida</i> Species of lichen

Buellia frigida is a species of saxicolous (rock-dwelling), crustose lichen in the family Caliciaceae. It was first described from samples collected from the British National Antarctic Expedition of 1901–1904. It is endemic to maritime and continental Antarctica, where it is common and widespread, at altitudes up to about 2,000 m (6,600 ft). The characteristic appearance of this lichen features shades of grey and black divided into small polygonal patterns. The crusts can generally grow up to 7 cm in diameter, although neighbouring individuals may coalesce to form larger crusts. One of the defining characteristics of the lichen is a textured surface with deep cracks, creating the appearance of radiating lobes. These lobes, bordered by shallower fissures, give the lichen a distinctive appearance and textured surface.

<i>Erichansenia</i> Genus of lichens

Erichansenia is a genus of lichen-forming fungi in the family Teloschistaceae. It has three species of saxicolous (rock-dwelling), crustose lichens.

Schaereria bullata is a species of lichen in the family Schaereriaceae. It is found in the alpine regions of Tasmania, Australia. This lichen species is characterized by its dark brown to grey-brown thallus, which forms irregular patches over soil or bryophytes, and consists of granules that coalesce to create convex to bullate squamules. The lichen also features distinctive apothecia, which are roundish and typically superficial, and spherical spores.

References

  1. 1 2 3 4 5 6 7 8 9 10 Büdel, B.; Scheidegger, C. (1996). "Thallus morphology and anatomy". In Nash, T. (ed.). Lichen biology. Cambridge: Cambridge University Press. pp. 37–41.
  2. ↑ Laursen, G.; Seppelt, R. (2010). Common interior Alaska cryptograms: Fungi, lichenicolous fungi, lichenized fungi, slime molds, mosses, and liverworts (2nd ed.). Fairbanks, Alaska: University of Alaska Press. pp. 122–124.
  3. ↑ Hawksworth, D.; Hill, D. (1984). The lichen-forming fungi. Glasgow: Blackie. pp. 16–22.
  4. 1 2 Perez-Llano, G.A. (1944). "Lichens: Their biological and economic significance". Botanical Review. 10 (1): 1–65. doi:10.1007/bf02861799. JSTOR   4353298.
  5. ↑ Baron, G. (1999). Understanding lichens. Slough, England: Richmond Publications. pp. 25–26.
  6. 1 2 Ahmadjian, V. (1967). The lichen symbiosis. Waltham, Massachusetts: Blaisdell Publications.
  7. 1 2 Richardson, D.H.S. (1975). The vanishing lichens : their history, biology and importance. Newton Abbot [Eng.]: David & Charles. ISBN   9780715365496.
  8. 1 2 Giordani, Paolo; Incerti, Guido; Rizzi, Guido; Rellini, Ivano; Nimis, Pier Luigi; Modenesi, Paolo; Güsewell, Sabine (May 2014). "Functional traits of cryptogams in Mediterranean ecosystems are driven by water, light and substrate interactions". Journal of Vegetation Science. 25 (3): 778–792. doi:10.1111/jvs.12119.
  9. ↑ Matos, Paula; Pinho, Pedro; Aragón, Gregorio; Martínez, Isabel; Nunes, Alice; Soares, Amadeu M. V. M.; Branquinho, Cristina; Schwinning, Susan (March 2015). "Lichen traits responding to aridity". Journal of Ecology. 103 (2): 451–458. doi:10.1111/1365-2745.12364.
  10. 1 2 Hale, M.E. (1973). "Growth". In Ahmadjian, V.; Hale, M.E. (eds.). The lichens. New York: Academic Press. pp. 473–492.
  11. ↑ Trenbirth, Hazel E.; Matthews, John A. (March 2010). "Lichen Growth Rates on Glacier Forelands in southern Norway Results from a 25-Year Monitoring Programme". Geografiska Annaler: Series A, Physical Geography. 92 (1): 19–39. doi:10.1111/j.1468-0459.2010.00375.x.
  12. ↑ McCarthy, Daniel P.; Henry, Nicole (2012). "Measurement of growth in the lichen Rhizocarpon geographicum using a new photographic technique". Lichenologist. 44 (5): 679–693. doi:10.1017/S0024282912000175.
  13. ↑ Osborn, Gerald; McCarthy, Daniel; LaBrie, Aline; Burke, Randall (January 2015). "Lichenometric dating: science or pseudoscience?". Quaternary Research. 83 (1): 1–12. doi:10.1016/j.yqres.2014.09.006.
  14. ↑ Round, F.E. (1969). Introduction to the lower plants . London: Butterworths. ISBN   9780408538008.
  15. 1 2 Jianhua, Cao; Fuxing, Wang (March 1998). "Reform of Carbonate Rock Subsurface by Crustose Lichens and Its Environmental Significance". Acta Geologica Sinica - English Edition. 72 (1): 94–99. doi:10.1111/j.1755-6724.1998.tb00736.x.
  16. ↑ Johnson, E. A.; Rowe, J. S. (July 1975). "Fire in the Subarctic Wintering Ground of the Beverley Caribou Herd". American Midland Naturalist. 94 (1): 1. doi:10.2307/2424533.
  17. ↑ Rai, Himanshu; Khare, Roshni; Baniya, Chitra Bahadur; Upreti, Dalip Kumar; Gupta, Rajan Kumar (16 December 2014). "Elevational gradients of terricolous lichen species richness in the Western Himalaya". Biodiversity and Conservation. 24 (5): 1155–1174. doi:10.1007/s10531-014-0848-6.
  18. 1 2 Hale, M.E. (1967). The biology of lichens. London: Arnold.
  19. ↑ Kitagawa, R.; Watanabe, K. (2004). "Alteration mechanism of biotite in granitic rock caused by crustose lichen "Porpidia"". Clay Science. 12 (4): 249–257. doi:10.11362/jcssjclayscience1960.12.249.
  20. ↑ Vartia, K.O. (1973). "Antibiotics in lichens". In Ahmadjian, V.; Hale, M.E. (eds.). The lichens. New York: Academic Press. pp. 547–561.
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