Umbilicaria cylindrica, also called fringed rock tripe, is a leafy lichen that grows in cold, high-altitude, and polar regions around the world. It forms round-shaped structures called thalli, which are 2–10 centimeters in size. These thalli have a dark top surface surrounded by a border of tiny, hair-like projections. As one of the first organisms to grow on bare rock, it helps create conditions for other plants and animals to live in areas with strong sunlight. This lichen is most common in Arctic and alpine regions, where it grows in large groups on exposed rocks.
Scientists first named this species in 1753 by Carl Linnaeus. Over time, researchers have changed its classification because of its different appearances and chemical properties. Although many names were once used for its various forms, recent studies show these differences are normal variations within a single species. Important features for identifying it include its maze-like reproductive structures called apothecia and its three-layered inside structure. The lichen can change in size, color, and texture depending on where it grows.
In addition to its scientific interest, Umbilicaria cylindrica plays a key role in the environment. As a pioneer species on rocky surfaces, it helps form soil and provides a home for fungi and other small organisms. It absorbs harmful substances like heavy metals and radioactive particles from the air, making it a natural sign of environmental health in remote alpine and Arctic areas. Its ability to detect pollution has made it useful for studying long-term changes in the environment, especially in places affected by industrial waste and nuclear activity.
Taxonomy
The species was first scientifically described by the Swedish taxonomist Carl Linnaeus, who classified it as part of the genus Lichen. In his 1753 description, Linnaeus described the species as a leafy lichen with hairy edges and fruiting bodies that are tube-shaped and have holes. These fruiting bodies show a "double circle" pattern on their surfaces, a feature still used today to identify the species. Linnaeus noted that the species grows in both Pennsylvania and Lapland, showing its wide geographic range. The key features he identified—hairy edges and unique fruiting bodies—remain important for identifying the species. The original sample collected in Sweden is stored in the Linnaean Herbarium in London. In 1830, the French botanist Dominique François Delise moved the species to the genus Umbilicaria, giving it the name it is known by today. During the 19th century, European lichenologists made many changes to the species' classification, creating many subcategories like forms, varieties, and subspecies based on physical differences. In his 1950 study of Umbilicariaceae in the Western Hemisphere, George Llano wrote that the species shows many variations and cannot be fully understood by examining only a few samples. He provided a guide to identify 13 varieties and forms of U. cylindrica, noting that this list did not cover all variations. While these older names are still recorded, they are no longer considered separate from the main form. Examples include var. fimbriata (with many dark bristles) and var. denticulata (with bristles that match the thallus color and lie flat).
The classification of U. cylindrica has changed over time. In their 1993 study of Asian Umbilicariaceae, Jian-chun Wei and Yu-mei Jiang reviewed earlier mistakes in classifying U. cylindrica and introduced the name U. neocylindrica for specimens that were incorrectly called U. cylindrica. They found that this error mainly affected Asian samples and that U. neocylindrica looks similar to U. umbilicarioides. However, U. cylindrica can be told apart from U. umbilicarioides by the lack of thalloconidia and the presence of visible bumps on its lower surface. While U. neocylindrica was proposed to fix naming issues, it is not widely accepted today and is not recognized as a separate species in recent genetic studies.
The species shows major differences in shape, chemistry, and genetics across its wide range. Studies have found many variations in enzymes and physical traits between populations, showing how adaptable the species is. Up to six varieties have been found in the Iberian Peninsula and five in the Tatra Mountains in Poland, each with unique features like the density of rhizines, surface texture, and thallus color.
In a 2017 study, Davydov and colleagues used genetic analysis to clarify the relationships of U. cylindrica. Their work placed U. cylindrica in "Clade 3" (subgenus Umbilicaria), grouping it with close relatives like U. altaiensis, U. dendrophora, U. maculata, and U. umbilicarioides. This group is defined by a raised, textured, or ridged center on the upper surface of the thallus. Studies have also found differences in chemical makeup, such as varying amounts of gyrophoric and lecanoric acids, as well as physical and biological differences. Species in this group are usually found in high mountain or subpolar areas, either in both hemispheres or limited to the Holarctic region.
In North America, Umbilicaria cylindrica is commonly called "fringed rock tripe."
Description
The lichen Umbilicaria cylindrica has a thallus that resembles a leaf. This thallus can grow up to 10 cm in diameter, though most specimens are smaller than 4 cm. One recorded specimen, previously called var. delisei, measured 26 cm in diameter. The thallus has multiple lobes that may be smoothly rounded or irregularly jagged, and some may have small holes. The upper surface is dark brown, dark grey, or black, and may have a grey, powdery coating in some areas. Its texture can be smooth or slightly rough with tiny, map-like cracks. Inside, the thallus has a three-layered medulla: an outer layer with a loose, web-like structure, a dense central layer where fungal threads are tightly packed, and a lower web-like layer. This "decussata-type" structure is unique to the species and allows the thallus to hold about 20% water in its pores.
The reproductive structures, called apothecia, are black, raised discs 0.5–2.0 mm in diameter (up to 4.0 mm in rare cases). These structures have a maze-like surface pattern and are raised on short stalks, with smooth or slightly cracked edges. Early research on this species was conducted by Gustav Lindau in the late 1800s. He observed that apothecia develop near the center of the thallus, slightly inward from the edge. Lindau noted that early apothecial growth begins below the algal layer, where hyphae form a coiled structure that later grows upward. Some scientists, like Wilhelm Baur, believed these hyphae were early paraphyses, a debate that reflected limited knowledge of lichen reproduction at the time.
The underside of the lichen is typically beige-brown or pinkish, sometimes grey, with darker color near the central attachment point (umbilicus). The lower surface is smooth and has root-like structures (rhizines) that match its color. These rhizines are cylindrical and may be simple or slightly branched. Older specimens may show slight cracking near the center. A distinctive feature of this species is its many root-like structures (rhizinomorphs) that grow from both the upper and lower surfaces, especially along the edges. These dark, glossy projections are 1–4 mm long, often branching into segments. They attach flat to the lichen body, then become cylindrical and taper to a point, sometimes forming small knob-like growths.
When reproducing sexually, the lichen produces simple, oval spores measuring 12–18 by 5–9 micrometers (μm). It can also reproduce asexually through smaller, rod-shaped structures (conidia) that measure 3–4 by 0.5–0.7 μm. It rarely forms other types of reproductive structures.
Development
Umbilicaria cylindrica grows in a unique way. Instead of spreading outward from the edges, new parts of the main body (called the thallus) grow on top of existing ones. This growth process involves both the main body and its special appendages. It usually starts when the outer layer breaks, either where algae cells push through weak spots or when tissue breaks down completely, creating holes for new growth to begin.
The lichen’s hair-like structures—both the edge hairs (marginal cilia) and root-like parts (rhizinomorphs)—form from the outer layer of the thallus. These structures are the same, but they grow in different places on the thallus. Their growth is linked to the thallus’s powdery surface coating (pruina). Even though they look different, studies show that the edge hairs and root-like parts develop in the same way, only appearing in different locations.
These appendages grow mainly in areas where the thallus is actively growing, not randomly. They are often found near breaks or holes in the thallus, along the edges of new parts, and around fruiting bodies. This pattern challenges older ideas that suggested the root-like parts on the upper surface were simply lower surface structures that had grown upward through the thallus.
The apothecia (reproductive parts) have a maze-like pattern called gyrose. This happens because the tissue that holds the spores (ascs) grows outward toward the edge of the structure, leaving a weak center. This center fills with sterile tissue (paraphyses). This process repeats, creating alternating bands of fertile and sterile tissue. The tips of the paraphyses turn black, making the apothecia appear dark. Spores are produced only after the fertile tissue has fully developed.
Chemistry
The lichen creates several types of secondary metabolites, such as tridepsides, depsidones, and orcinol derivatives. The main compound is gyrophoric acid, a tridepside, which is usually found along with smaller amounts of lecanoric acid, an earlier compound in its production. Other compounds found in U. cylindrica include umbilicaric acid (a version of gyrophoric acid with a methyl group), ovoic acid, and hiascic acid.
Studies using high-performance liquid chromatography (HPLC) have shown more chemical differences than earlier methods had found. Gyrophoric acid is always present in the species, but some samples have very small amounts, making it hard to detect in small samples. Research has also found differences in the types and amounts of secondary metabolites based on location, with some U. cylindrica populations having different ratios of gyrophoric acid to its related compounds.
HPLC results also suggest that other compounds, such as crustinic acid (a tridepside with a hydroxyl group) and methylated versions of gyrophoric acid, may be present in very small amounts. However, these are often hard to detect because gyrophoric acid is usually present in large amounts.
Extracts from the lichen show antioxidant effects, especially because gyrophoric acid has a structure with many hydroxyl groups. Some studies have also found antimicrobial activity against bacteria and fungi, which is linked to the presence of usnic acid and other phenolic compounds.
Similar species
Umbilicaria cylindrica can be recognized by its unique, tassel-like rhizinomorphs, which make it different from similar species. These root-like structures are long and slightly flattened, growing from the edges of jagged lobe shapes in a way that looks like decorative tassels on a rug. They have a smooth surface and do not contain specialized reproductive granules (thalloconidia).
The most similar species is U. umbilicarioides, which can be difficult to tell apart, especially since the two often grow in the same area. U. umbilicarioides has shorter rhizinomorphs (usually no longer than 1.5 mm) that branch densely in a bushy or coral-like pattern. These structures form a distinct, shrub-like edge where they appear suddenly from the lichen lobes and can be recognized by their clusters of reproductive granules. These species often grow together, so it is common to find them mixed in herbarium samples. Another similar species is U. maculata, which can be identified by its shorter rhizinomorphs, sessile (unstalked) apothecia with a unique pattern of sterile cracks, and an upper surface that often shows white stains or mottling. While U. virginis has rhizines that extend outward like U. cylindrica, it can be distinguished by its smooth disc, which contrasts with U. cylindrica’s wavy pattern. Additionally, U. virginis’s medulla turns red when tested with C and KC chemicals, showing the presence of gyrophoric acid—a compound not found in U. cylindrica. The closely related Dermatocarpon miniatum, which grows on limestone instead of silicate rocks, lacks bristles and has fruiting bodies that are sunken rather than raised.
Habitat and distribution
Umbilicaria cylindrica is a lichen that lives in cold, mountainous areas of the Arctic and alpine regions. It grows on rocky surfaces that are exposed to wind and cold, such as granite and basalt, which are types of acidic rocks. This lichen is usually found in the alpine zone above the tree line, where it grows on rocks and outcrops that are often covered by snow only briefly during the year. In the Alps, it is found at elevations from about 1,000 meters up to the highest areas, such as 4,270 meters on the Finsteraarhorn. This lichen can survive extreme conditions, including strong sunlight, repeated freezing and thawing of ice, and long periods without water. In Greenland, it is rare in highland and coastal areas because of dry winds called Foehn winds, but it grows at higher coastal elevations up to 1,600 meters where these winds have less effect. Instead of being one of the first plants to grow in an area, it lives in specific protected places.
Umbilicaria cylindrica is found around the North Pole and is common in Arctic and boreal-alpine areas of the Northern Hemisphere. It is present in North America, Europe, and Asia, especially in high mountain regions. For example, it grows in northern parts of Scandinavia and Russia (Arctic tundra) and in high mountains of Europe, such as the Alps and Carpathians, as well as in Asia. It is also found in the Himalayas, including the Nandi Kund area in Uttarakhand, India, where it grows on rocks and soil at about 4,800 meters. Outside its main range in the Northern Hemisphere, it has been found in some high-altitude areas of the Southern Hemisphere, such as in Tasmania, southeastern Australia, and New Zealand.
Ecology
In its alpine habitats, U. cylindrica often grows as part of communities where lichens are the main plants on bare rock. It is a pioneer species that colonizes newly exposed surfaces, such as glacier forefields, helping to start soil formation and the development of ecosystems on barren rock. Its ability to survive in harsh conditions allows it to grow on surfaces few other organisms can, and its mature thalli can last for many years, slowly expanding and often becoming the main plant in its small area. On sunny, wind-exposed ridges and plateaus, U. cylindrica often grows with other tough lichens (such as species of Cetraria, Stereocaulon, Rhizocarpon) and moss-like plants, although overall plant cover remains low. In Arctic areas, it can be one of the most common leafy lichens on flat rock surfaces, covering about 5–8% of some lichen communities.
Umbilicaria cylindrica is known to host specialized fungi (called lichenicolous fungi) that live on or inside its thallus. Several species of these fungi have been found on U. cylindrica. For example, the fungus Stigmidium gyrophorarum infects the thallus of U. cylindrica, forming small black structures called perithecia on its surface. Another fungus, Lichenostigma epiumbilicariae, lives on U. cylindrica and creates dark, thread-like growths on the top surface of the thallus. This fungus specifically targets U. cylindrica and other Umbilicaria species, but it does not harm the lichen’s tissues, as its growth is limited to the dead outer layer of the thallus. Straminella printzenii is a lichen that lives on other lichens and is found in Europe; its main host is U. cylindrica.
On rock surfaces, U. cylindrica competes with other lichens and algae for space and light. Its thick, tough thallus and ability to survive extreme conditions give it an advantage on open, horizontal surfaces with strong sunlight and wind. However, it does not grow in shaded areas or on vertical cliff faces, where other Umbilicaria species (such as U. decussata) or orange crust-like lichens may be more common. This suggests niche partitioning: U. cylindrica grows on top surfaces and gentle slopes, while other species occupy steeper or shaded areas. When in direct contact with other organisms, U. cylindrica’s slow growth can allow faster-growing lichens or mosses to overtake it at the edges, especially if conditions become less extreme. However, in its preferred alpine environments with high stress (such as freezing and thawing, and intense sunlight), it faces little competition and can form nearly single-species patches on rock.
Biomonitoring
Umbilicaria cylindrica is a type of lichen that does not have roots and takes in nutrients directly from the air, rain, and dust. Because it absorbs pollutants from the environment, it is used as a tool to study air quality and pollution. Over time, harmful substances like heavy metals build up in its tissues, making it helpful for scientists to monitor environmental changes. This lichen is found in many areas and can collect metals and other contaminants, which helps researchers understand pollution levels. Scientists have studied samples of U. cylindrica from different places to measure the amounts of metals, radioactive materials, and other chemicals in the air. Since this lichen lives for a long time and does not move, it provides a record of pollution over time in a specific location.
In areas affected by industry or mining, the lichen’s tissues contain higher levels of metals such as lead, zinc, copper, and chromium. A study in the Sudety region of Poland found that several lichen species, including U. cylindrica, had collected large amounts of metals like chromium, copper, and lead. These lichens trap tiny particles from the air, and their tissues are used to map where pollution spreads. This shows that U. cylindrica can survive in areas with some pollution while still collecting harmful substances, making it a useful tool for studying heavy metals.
U. cylindrica can also help track radioactive materials from nuclear events. When nuclear tests or accidents release radioactive particles, such as caesium-137, these materials settle on soil and plants. In a study in Poland, scientists tested lichens at different heights and found measurable levels of caesium, with higher concentrations at higher elevations. This showed that U. cylindrica can act as a natural tool to measure radioactive pollution over time in remote mountain areas. Scientists have also studied lichens in Arctic regions and areas near Chernobyl to track how long radioactive contamination lasts.
U. cylindrica has been used to study changes in air pollution over time. In the French Alps, researchers measured fluorine levels in U. cylindrica between 1975 and 1985 to see how a nearby aluminum smelter affected air quality. Over ten years, the fluorine content in the lichen decreased, showing that pollution levels dropped as the smelter reduced its emissions. This was one of the first times lichens were used to show that pollution controls improved air quality. Lichens like U. cylindrica are also sensitive to sulfur dioxide and acid rain, so their presence or health can indicate good air quality. These lichens grow well in clean mountain air but may show damage or disappear in highly polluted areas. Scientists use both the chemical content of U. cylindrica and its physical condition to monitor the environment.
Recognition
In 2018, U. cylindrica was chosen as "Lichen of the Year" by the Bryologisch-lichenologische Arbeitsgemeinschaft für Mitteleuropa (BLAM), a Central European group that studies mosses, lichens, and other small plants. This selection highlighted the species as a common plant in high mountain areas and one of the first plants to grow on bare rock.