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 hybrid colony of algae or cyanobacteria living symbiotically among filaments of multiple fungi species, along with a yeast embedded in the cortex or "skin", in a mutualistic relationship.

<i>Sarcogyne</i> Genus of lichens

Sarcogyne is a genus of crustose lichens in the family Acarosporaceae. It was circumscribed by German botanist Julius von Flotow in 1850. A proposal has been put forth in 2021 to assign Sarcogyne clavus as the type species of the genus, "as it represents the original concept of Sarcogyne as having melanized lecideine apothecia without algae in the margin".

<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.

Stromatella bermudana is a saxicolous (rock-dwelling) crustose lichen. It is the only species in Stromatella, a monotypic fungal genus in the family Lichinaceae.

<i>Peltula</i> Genus of lichen-forming fungi

Peltula is a genus of small dark brown to olive or dark grey squamulose lichens. These lichens typically grow on rocks in arid and semi-arid environments worldwide. They consist of a fungus living in symbiosis with a photosynthetic partner, specifically a cyanobacterium of the genus Chroococcidiopsis. Peltula is the only genus in the family Peltulaceae, which belongs to the Lichinomycetes, a class of fungi that form lichens. The genus includes about 50 recognised species, which exhibit a variety of growth forms ranging from flat and crust-like to more complex, leaf-like structures. Peltula lichens play important ecological roles in harsh environments, contributing to soil stability and nutrient cycling.

<span class="mw-page-title-main">Lecideaceae</span> Family of lichen-forming fungi

The Lecideaceae are a family of lichen-forming fungi in the order Lecideales. It contains about 30 genera and roughly 250 species. A major distinguishing characteristic of the family is the lecanoroid form of the fruiting bodies: typically circular, dark, and without a thalline margin. Most species in the family are lichenised with green algae, although a few species, scattered amongst several genera, are lichenicolous—they live on other lichens. Lecideaceae lichens tend to grow on rocks, wood, and soil. Several Lecideaceae species accelerate the weathering of rock surfaces, a process known as pedogenesis, by extending their hyphae into cracks and expelling rock flakes. This contributes to significantly faster weathering rates in certain environments, impacts various materials from natural rocks to man-made Sekishu roof tiles, and involves key biomolecules identified for survival and biodeterioration, including compounds to withstand intense ultraviolet radiation.

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.

<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 are 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>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>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.

Caloplaca himalayana is a species of lignicolous (wood-dwelling) crustose lichen belonging to the family Teloschistaceae. Found in the Himalayas of India, it was described as new to science in 2009. The lichen has a yellowish thallus with rusty red apothecial discs.

Acarospora toensbergii is a species of saxicolous (rock-dwelling), crustose lichen in the family Acarosporaceae. Known only from the Kenai Fjords National Park in Alaska, it was described as a new species in 2017 by the lichenologists Kerry Knudsen and Jana Kocourková. The species epithet honors the Norwegian lichenologist Tor Tønsberg, who collected the type specimen from a deglaciated alluvial terrace in 2015.

<i>Lepraria xerophila</i> Species of lichen

Lepraria xerophila is a species of leprose lichen in the family Stereocaulaceae. Found in Europe and northwestern North America, it was formally described as a new species in 2004 by the Norwegian lichenologist Tor Tønsberg.

<i>Lepraria bergensis</i> Species of lichen

Lepraria bergensis is an uncommon crustose lichen in the family Stereocaulaceae. It occurs in Northern and Central Europe, where it grows on siliceous (silicon-rich) rock walls, particularly under small overhangs, and on mosses on vertical to slightly sloping rock surfaces. The lichen thallus forms as a pale bluish-grey crust-like growth on rocks and mosses. The lichen begins as small, rounded patches a few millimetres wide, which may eventually coalesce into larger areas exceeding 1 centimetre in diameter. The thallus has a powdery texture, consisting of minute granules known as soredia and consoredia, which facilitate the lichen's asexual reproduction. The chemical composition of Lepraria bergensis is distinguished by the presence of several secondary metabolites: atranorin, rangiformic acid or jackinic acid, trace amounts of their respective derivatives, and a variety of anthraquinones. These chemical components cause the lichen to fluoresce a dull yellow under long-wave ultraviolet light.

<i>Aspilidea</i> Single-species lichen genus

Aspilidea is a fungal genus of uncertain familial placement in the subclass Ostropomycetidae. It contains the single species Aspilidea myrinii, a saxicolous (rock-dwelling) crustose lichen with a circumpolar distribution.

Pseudopeltula is a genus of lichen-forming fungi in the family Gloeoheppiaceae. Established in 1995 by the lichenologist Aino Henssen, the genus currently includes four recognised species. These small cyanolichens are characterised by their squamulose (scaly) to peltate (shield-shaped) thalli, which lack a lower cortex and are attached to the substrate by rhizines. A key feature of Pseudopeltula is its complex apothecia, which have hymenia that often become divided by sterile tissue as they mature. The genus is primarily found in arid and semi-arid regions of North America, Mexico, and the Caribbean, where species typically grow on soil, rock, or thin soil over rock, often forming part of biological soil crusts in desert environments.

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. Bibcode:1944BotRv..10....1P. doi:10.1007/bf02861799. JSTOR   4353298. S2CID   32376858.
  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. Bibcode:2014JVegS..25..778G. 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. Bibcode:2015JEcol.103..451M. 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. S2CID   128826239.
  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. hdl: 10464/3941 . S2CID   86401583.
  13. ↑ Osborn, Gerald; McCarthy, Daniel; LaBrie, Aline; Burke, Randall (January 2015). "Lichenometric dating: science or pseudoscience?". Quaternary Research. 83 (1): 1–12. Bibcode:2015QuRes..83....1O. doi:10.1016/j.yqres.2014.09.006. S2CID   129025304.
  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. Bibcode:1998AcGlS..72...94C. doi:10.1111/j.1755-6724.1998.tb00736.x. S2CID   128849403.
  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): 1–14. doi:10.2307/2424533. JSTOR   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. S2CID   254283966.
  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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