Rhizocarpon geographicum | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Lecanoromycetes |
Order: | Rhizocarpales |
Family: | Rhizocarpaceae |
Genus: | Rhizocarpon |
Species: | R. geographicum |
Binomial name | |
Rhizocarpon geographicum | |
Rhizocarpon geographicum (the map lichen) is a species of lichen, which grows on rocks in mountainous areas of low air pollution. Each lichen is a flat patch bordered by a black line of fungal hyphae. These patches grow adjacent to each other, leading to the appearance of a map or a patchwork field.
When circular, or roughly circular, the diameter of this lichen species has been widely used to help determining the relative age of deposits, e.g. moraine systems, thus revealing evidence of glacial advances. The process is termed lichenometry. This technique is generally attributed to the work of Roland Beschel in the Alps. [1]
Lichenometry is based on the assumption that the largest lichen growing on a rock is the oldest individual. Generally, the five largest lichen thalli diameters are taken, although several statistical methods have been used. If the growth rate is known, the maximum lichen size will give a minimum age for when this rock was deposited. The growth rate curve, a graph of age of a lichen against the date of the substrate on which it is found has to be constructed for an area. Beschel originally used gravestones to produce a calibration curve. Growth rates for different areas and species can be obtained by measuring maximum lichen sizes on substrates of known age, such as gravestones, historic or prehistoric rock buildings, or moraines of known age (e.g. those deposited during the Little Ice Age).
This lichen species is broadly distributed and may be found in most cold areas with exposed rock surfaces. The North American range includes the Sierra Nevada [2] and northern Boreal forests of Canada, Greenland, Iceland, Fennoscandia and Siberia. [3] In the tropics it only occurs at high altitudes such as the Andes of Peru and Colombia. Further south the map lichen is found broadly across Patagonia, [4] [5] in the Falkland Islands, the sub Antarctic islands and the Antarctic Peninsula. [6]
In Britain it can be found commonly growing on hard siliceous rocks, especially in upland regions. Its range covers virtually all of Scotland, much of North West England, and other upland areas in much of the rest of England, Wales and Ireland too. [7]
In Spain it is found primarily in siliceous mountain ranges, although occasionally it can be found near sea level, even in southern Spain, where it is known from Cabo de Gata. [8]
Rhizocarpon geographicum is a known host to the lichenicolous fungus species Muellerella pygmaea . [9]
One specimen of Rhizocarpon geographicum on East Baffin Island has an estimated age of 9500 years. [10] [11] Thalli of Rhizocarpon geographicum in the central Brooks Range of northern Alaska have been given a maximum possible age of 10,000–11,500 years. [12] [13]
In an experiment, this lichen species was placed in a capsule and launched into space. The capsule was opened, exposing the lichen to space conditions for 10 days before being brought back down to Earth, where it showed minimal changes or damage. [14]
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.
Cladonia rangiferina, also known as reindeer cup lichen, reindeer lichen or grey reindeer lichen, is a light-coloured fruticose, cup lichen species in the family Cladoniaceae. It grows in both hot and cold climates in well-drained, open environments. Found primarily in areas of alpine tundra, it is extremely cold-hardy.
In archaeology, palaeontology, and geomorphology, lichenometry is a geomorphic method of geochronologic dating that uses lichen growth to determine the age of exposed rock, based on a presumed specific rate of increase in radial size over time. Measuring the diameter of the largest lichen of a species on a rock surface can therefore be used to determine the length of time the rock has been exposed. Lichen can be preserved on old rock faces for up to 10,000 years, providing the maximum age limit of the technique, though it is most accurate when applied to surfaces that have been exposed for less than 1,000 years. Lichenometry is especially useful for dating surfaces less than 500 years old, as radiocarbon dating techniques are less accurate over this period. The lichens most commonly used for lichenometry are those of the genera Rhizocarpon and Xanthoria. The measured growth rates of R. geographicum tends to fall within the range of 0.9–0.3 millimeter per year, depending on several factors, including the size of the lichen patch.
Rusavskia elegans, commonly known as the elegant sunburst lichen, is a lichenized species of fungus in the genus Rusavskia, family Teloschistaceae. Recognized by its bright orange or red pigmentation, this species grows on rocks, often near bird or rodent perches. It has a circumpolar and alpine distribution. It was one of the first lichens to be used for the rock-face dating method known as lichenometry.
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.
Rhizocarpon is a genus of crustose, saxicolous, lecideoid lichens in the family Rhizocarpaceae. The genus is common in arctic-alpine environments, but also occurs throughout temperate, subtropical, and even tropical regions. They are commonly known as map lichens because of the prothallus forming border-like bands between colonies in some species, like the common map lichen.
Crustose lichens are lichens that form a crust which strongly adheres to the substrate, making separation from the substrate impossible without destruction. 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. 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.
A lichenicolous fungus is a member of a specialised group of fungi that live exclusively on lichens as their host organisms. These fungi, comprising over 2,000 known species across 280 genera, exhibit a wide range of ecological strategies, including parasitism, commensalism, and mutualism. They can be found in diverse environments worldwide, from tropical to polar regions, and play important roles in lichen ecology and biodiversity. Lichenicolous fungi are classified into several taxonomic groups, with the majority belonging to the Ascomycota and a smaller portion to the Basidiomycota. Their interactions with host lichens range from mild parasitism to severe pathogenicity, sometimes causing significant damage to lichen communities.
Placopsis perrugosa is a saxicolous (rock-dwelling), placodioid lichen in the family Trapeliaceae. It was formally described as a new species in 1867 by Finnish lichenologist William Nylander, originally as a member of the genus Lecanora.
Cetraria aculeata or the spiny Iceland lichen is a dark brown to black fruticose, soil Iceland lichen from the family Parmeliaceae. The species was first described by German naturalist Johann Christian Daniel Edler von Schreber in 1771 under the name of Lichen aculeatus. Later on, Erik Acharius, the "father of lichenology" gave it a name of Cornicularia aculeata, which lately has been changed to Coelocaulon aculeatum. Finally, the taxonomic revision of Ingvar Kärnefelt and colleagues assigned the species to the genus Cetraria.
Roland Ernst Beschel was an Austrian botanist, lichenologist, professor, and herbarium director, known for his famous doctoral thesis and subsequent research on lichenometry.
Lecanora polytropa, the granite-speck rim lichen, is a species of saxicolous (rock-dwelling), crustose lichen in the family Lecanoraceae. A small, inconspicuous species that grows in the cracks of rock surfaces, it has a cosmopolitan distribution and has been recorded on all continents, including Antarctica.
Umbilicaria hyperborea, commonly known as blistered rock tripe, is a species of foliose lichen in the family Umbilicariaceae. It is widely distributed in arctic and alpine regions.
Muellerella ventosicola is a species of lichenicolous fungus in the family Verrucariaceae. It shows preference to growing on species of the genus Rhizocarpon but can also associate with other genera.
Muellerella pygmaea is a species of lichenicolous fungus in the family Verrucariaceae. It has a cosmopolitan distribution in Arctic-alpine areas and grows on the thallus and apothecia of a number of hosts.
Sporastatia is a genus of crustose lichens in the family Sporastatiaceae. It has four species. Sporastatia lichens are long-lived species that grow on siliceous or weakly calcareous rocks in arctic and alpine locales.
Lecanora lojkahugoi is a species of saxicolous (rock-dwelling) crustose lichen in the family Lecanoraceae. It is found in the Russian Far East and in South Korea.
Erichansenia epithallina is a species of saxicolous (rock-dwelling), crustose lichen in the family Teloschistaceae. It is also a lichenicolous lichen species, meaning that it grows on other lichens. Many host genera have been recorded. It occurs in Europe and North America, including Arctic regions.
Rhizocarpon pusillum is a species of saxicolous (rock-dwelling), crustose lichen in the family Rhizocarpaceae. It is a lichenicolous lichen, meaning it is parasitic on other lichens. It was formally described as a new species in 1956 by the Swedish lichenologist Hans Runemark.
Arctoparmelia incurva is a species of saxicolous (rock-dwelling), foliose lichen in the family Parmeliaceae. First described in 1794 by Christiaan Hendrik Persoon, it has undergone several taxonomic reclassifications before being placed in its current genus in 1986. This yellowish-green lichen, characterised by its narrow, convex lobes and globular soralia, typically grows on sun-exposed siliceous rocks in alpine and arctic habitats. It has a circumpolar distribution, found across North America, Europe, and parts of Asia. A. incurva can be distinguished from similar species by its specific morphological features and chemical spot test reactions. The lichen is known to host several parasitic fungi and has shown tolerance to acid pollution.