Umbilicaria torrefacta is a species of saxicolous (rock-dwelling), foliose lichen in the family Umbilicariaceae.[2] It is an arctic-alpine species with a circumpolar distribution and is widely distributed within the Holarctic realm, specifically within the Palearctic and Neoarctic biogeographical regions. Characteristic features of Umbilicaria torrefacta include the lace-like fringe in its lobes and the plates on the underside of the thallus. One common name, punctured rock-tripe, refers to the distinctive sieve-like perforations on the thallus margins.
The species was scientifically described in 1777 by John Lightfoot and later classified under the genus Umbilicaria by Heinrich Schrader in 1794. Because of its somewhat variable morphology, this species has often been misidentified historically and described under different names, resulting in an extensive synonymy. In 2017, a lectotype specimen was designated for the species, clarifying its taxonomic status. Molecular phylogenetics studies have revealed complex relationships within the family Umbilicariaceae, resulting in the revision of the genus Umbilicaria. U.torrefacta is a member of Gyrophora, a subgenus characterised by species with circular ridges on the discs of their apothecia; rigid, non-pustulate thalli; and specific secondary metabolites, such as gyrophoric acid and stictic acid.
Umbilicaria torrefacta has distinct spectral properties, transmitting very little light and significantly altering the spectral signature of rock surfaces. It shows slow initial growth and delayed reproduction, with reproductive output increasing linearly with thallus size. The population structure is skewed towards smaller individuals, indicating ongoing recruitment and colonisation in newly exposed areas. These characteristics enable U.torrefacta to adapt and maintain a stable presence in challenging alpine environments.
Umbilicaria torrefacta can be compared to U.dura, U.multistrata, and U.semitensis, all of which share similarities in appearance but can be distinguished by differences in spore type, thallus structure, colouration, and chemical components, with specific distinctions in geographical distribution and spore size. Umbilicaria torrefacta has historical significance in the Scottish Highlands for its use as a natural dye in wool and fabric, producing a range of purplish-red to greyish-magenta hues, with the fermentation method yielding rich red and purple dyes, valued for traditional tartans and textiles.
Taxonomy
Umbilicaria torrefacta was first described and named in 1777 by the English parson-naturalistJohn Lightfoot, as Lichen torrefactus. The type specimen was collected by Lightfoot in the Scottish Highlands. He called it a "sad-colour'd crumpled Lichen, with black curled warts" and noted that it was "frequent upon the highland rocks".[3] The species epithettorrefacta comes from the Latin word meaning "roasted", which aptly describes the lichen's dark brown, glazed upper surface.[4] In 1794, Heinrich Schrader reclassified the species under the genus Umbilicaria,[5] resulting in the current binomial name, Umbilicaria torrefacta. The genus name Umbilicaria was introduced by Georg Franz Hoffmann, and it includes mostly rock-dwelling species primarily found in boreal, alpine, and Arctic regions worldwide.[4]
One of Dillenius' herbarium specimens, illustrated here as image #118 on plate 30 of Historia muscorum, was chosen to be the lectotype of Umbilicaria torrefacta.
Lightfoot's description highlighted several key features of the lichen. He observed that it consists of one or several leaves of a somber black, brown, or dull hue, connected at the base by a central point or umbilicus . He noted the upper side to be wrinkled with lobed and uneven margins, and a higher concentration of thin, compressed fibres and granulation towards the centre. The space between the fibres is finely granulated, and he compared the resulting slight roughness similar to the texture of shagreen, a type of textured leather. He also described the fruiting bodies as numerous, wrinkled, black sessile tubercles that seem to be composed of curled hairs, resembling those of Umbilicaria cylindrica, though less regular and less shiny. Lightfoot remarked that this lichen was represented in one of the well-known images of cryptogams depicted by Johann Jacob Dillenius in his 1741 work Historia muscorum.[3]
Umbilicaria torrefacta is known for its distinctive sieve-like perforations on the thallus margins, leading to vernacular names such as "punctured rock-tripe",[6] or "perforated rock-tripe".[4] The perforations may be more readily seen if held up against a light.[7] This characteristic feature makes it relatively easy to distinguish from other species within the genus.[4] "Torn brain-moss" is a historical vernacular name for the species that was suggested by Samuel Frederick Gray in 1821.[8]
Despite detailed early descriptions, proper typification of U.torrefacta faced challenges due to a history of synonyms and misidentifications. In 2017, Geir Hestmark designated a lectotype from the herbarium of Dillenius, which corresponds well with Lightfoot's original description. This lectotypification has clarified the taxonomic status, aiding in accurate identification and classification within the genus Umbilicaria. This step has been crucial in resolving historical taxonomic ambiguities and ensuring consistency with names used in the scientific literature.[4]
Over the years, molecular phylogenetics studies have revealed the complex relationships within the family Umbilicariaceae. These studies indicate that the traditional classification of the genus Umbilicaria was paraphyletic, meaning that it did not include all descendants from a common ancestor. As a result, the genus has been re-evaluated and revised based on molecular data. U.torrefacta is part of the subgenusGyrophora, which is characterised by its rigid, non-pustulate thalli and specific chemical compounds, including gyrophoric and lecanoric acids. The species in subgenus Gyrophora typically have smooth or granular upper surfaces and lack the pustulate structures seen in some other members of the family. This group is primarily distributed in the Holarctic region, covering both northern North America and Eurasia. The morphological traits and secondary metabolites of U.torrefacta help in distinguishing it from other related species within the subgenus.[9]
Synonymy
Due to its somewhat variable morphology, this species has been referred to in the earlier literature under various names. In 1778, Georg Heinrich Weber called it Lichen erosus,[10] and several synonyms were created then this epithet was recombined into several different genera. At some point, some authors referred to torrefacta as a variety or form of erosus, even though it was published a year earlier and thus had priority. The epithet torrida has also been used for the species ever since Erik Acharius referred to the species as Gyrophora erosa var. torrida,[11] and that epithet was used by later authors in different combinations.[12]
Description
Closeup of gyrose apothecia of Umbilicaria torrefactaThallus underside
Umbilicaria torrefacta is a lichen with a thallus that ranges from 2 to 6cm (3⁄4 to 2+3⁄8in) in diameter and consists of a single lobe . The thalli are typically monophyllous —connected to the substrate at a single point of attachment called an umbilicus . The thallus is often crumpled, with the edges finely dissected and perforated by small holes, giving it a lace-like appearance. These perforations may occasionally appear towards the centre.[13] The upper surface colour ranges from brown to dark brown,[7] and can be either smooth or have a cracked, wart-like texture.[13] Another source more emphatically suggests that the cracks in the upper surface, likened to "sutures in a skull", are characteristic of this species.[14] The lower surface varies from pale brown to black and features irregular, thin, somewhat flattened layers resembling plates (trabeculae) that are often torn or perforated.[13] Although rhizines (root-like structures) are absent in this species, torn fringes of trabeculae may be mistaken for rhizines.[7] When U.torrefacta is rewet after being dried, it emits a scent reminiscent of tea leaves.[15]
Apothecia (fruiting bodies) are common and measure 0.5 to 2mm in diameter. They are slightly immersed in depressions on the thallus and have a twisted, gyrose appearance with black discs . The paraphyses (sterile filaments among the spores) are unbranched with brown tips. The ascospores (spores produced in the fruiting bodies) are colourless, hyaline (translucent), ellipsoid in shape, and not divided by septa (internal partitions). Different spore measurements have been reported in the literature: 7 to 16.5μm long by 5 to 10μm wide from a European source,[13] and 8 to 12μm long by 4 to 6μm wide from a North American source.[7]Thalloconidia (asexual reproductive spores) are absent.[13]
In anatomical studies, the thallus of U.torrefacta shows considerable variability in the thickness of its layers. For instance, the algal layer thickness ranges from 25 to 65μm, and the medulla varies between 40 and 105μm. The upper cortex is typically 10 to 25μm thick, while the lower cortex ranges from 15 to 27.5μm. These adaptations help the lichen optimise photosynthesis and maintain hydration under different environmental conditions.[16]
The medulla of Umbilicaria torrefacta is classified as the "Ruebeliuna" type. This type is characterised by scleroplectenchyma , which means it consists of tightly packed hyphae without a preferential orientation. Both transverse and radial sections of this medulla have a similar appearance, resembling an arachnoidal (spider web-like) network of hyphae. The cells within these medullae are even more densely packed than in the "Deusta" type, resulting in narrow protoplasts that are challenging to observe under normal light microscope magnifications.[17]
Chemical tests reveal that the medulla (the inner layer of the thallus) reacts with certain chemical spot tests: it turns C+ (red) and KC+ (red), indicating the presence of gyrophoric acid and lecanoric acid. It remains unreactive with K and Pd. However, when stictic acid is present, the medulla reacts K+ (yellow) and Pd+ (orange).[13]
Similar species
The underside of Umbilicaria angulata also features plates positioned close to the umbilicus, but his species typically has branched, cylindrical rhizines. Another lookalike, Umbilicaria hyperborea. has a thallus surface similar to U.torrefacta and can even develop slight perforations; however, its lower surface is predominantly smooth.[6]
Umbilicaria torrefacta can be compared to Umbilicaria semitensis, which has several distinct features despite their superficial similarities. Both species inhabit rocky environments, but U.semitensis is found from southern California to southern Oregon, often at higher elevations, such as in Yosemite National Park. One notable difference between the two species is the spore type: U.semitensis has larger muriform spores, whereas U.torrefacta possesses smaller, simpler spores. Additionally, the lower surface of U.semitensis can vary from dark brown to black with distinct rhizines, sometimes giving it a similar appearance to U.torrefacta. However, U.torrefacta is usually characterised by a paler brown lower surface with plates (trabeculae) and rhizines, distinguishing it from the typically darker U.semitensis. These differences in spore morphology and thallus structure are critical aspects for accurate identification in the field.[18]
Umbilicaria dura, described as a new species in 2018, is similar in appearance to Umbilicaria torrefacta but can be distinguished by its tougher, thicker thallus and darker colouration. The lower surface of U.dura is dark brown to black, featuring one to several layers of trabeculae and rhizines, which contribute to its multilayered appearance. In contrast, U.torrefacta typically has a lighter lower surface with a single layer of trabeculae. Chemically, U.dura contains gyrophoric acid as a major component and lacks umbilicaric acid, which is sometimes present in U.torrefacta. The spores of U.dura are also generally smaller, measuring 7.5–9.5μm in length compared to those of U.torrefacta. U.dura is primarily found in Alaska and the Cascade Range of Oregon and Washington, preferring semi-sheltered rock faces.[19]
Umbilicaria multistrata, another species described in 2018, closely resembles U.torrefacta. It is characterised by a thick thallus and a black lower surface with multiple layers of trabeculae and rhizines, similar to U.dura. However, U.multistrata can be distinguished by the presence of umbilicaric acid in addition to gyrophoric acid, which is not found in U.torrefacta. The spores of U.multistrata are slightly larger, typically measuring 8.8–11.0μm in length. U.multistrata is known only from Alaska, where it grows on steeply sloping, somewhat sheltered surfaces of noncalcareous rock. While U.torrefacta can occasionally have a black lower surface and a moderately thick thallus, it usually does not develop the extensive multilayered trabeculae seen in U.multistrata.[19]
Umbilicaria torrefacta can be distinguished from Umbilicaria nodulospora by the latter's greyish-brown thallus, which often develops deep cracks and has angular to stellate juvenile apothecia. U.nodulospora also features a rhizinate lower surface and produces asymmetric, nodulose ascospores, in contrast to the symmetrical, ellipsoid ascospores of U.torrefacta. Additionally, U.nodulospora is primarily found on basalt in central Oregon to northeastern California, preferring steep, north-facing slopes.[20]
Umbilicaria torrefacta has distinct spectral properties that have been studied to understand its interaction with light and the implications for remote sensing. Reflectance spectra for U.torrefacta range from 3% to 7% in the visible spectrum, which is relatively low due to the presence of chlorophyll and other pigments that absorb light. This lichen species, like many others, shows specific absorption features near 685nanometres (nm) associated with chlorophyll, making it identifiable through hyperspectral imaging. The reflectance gradually increases in the near-infrared region, peaking around 1860nm.[22]
Studies on light transmittance through U.torrefacta demonstrate that it transmits very little light, typically less than 3% across the 350–2500nm spectral range. This low transmittance means that U.torrefacta effectively masks the underlying rock substrate, preventing light from penetrating through the lichen to the rock beneath. This characteristic is crucial for remote sensing applications, as it indicates that the presence of U.torrefacta can significantly alter the spectral signature of rock surfaces, necessitating the use of spectral unmixing techniques to differentiate between lichen-covered and bare rock areas.[22]
Growth and reproduction
Umbilicaria torrefacta in Finland
Umbilicaria torrefacta has a pattern of growth characterised by rapid initial expansion followed by a gradual slowdown as it approaches its maximum size. A study conducted over a 240-year chronosequence in the foreland of the Hellstugubreen glacier in Jotunheimen National Park, Norway, found that the initial growth rate of U.torrefacta is relatively slow compared to other Umbilicaria species, averaging 0.9mm per year. The maximum observed thallus diameter was 47mm, with the growth period extending to approximately 107years. This growth pattern reflects a common trend among alpine lichens, where rapid early growth is followed by a stabilisation phase as the lichen matures.[23]
Reproduction in U.torrefacta is closely related to thallus size. Apothecium production increases with the size of the thallus, with the first fertile individuals appearing at around 8 to 12mm in diameter. However, U.torrefacta tends to start reproducing later than some of its relatives, such as U.hyperborea, which begins to reproduce at smaller sizes. The reproductive output continues to grow with thallus size, but the trend is more linear compared to the exponential reproductive increase seen in U.hyperborea. This suggests a more steady reproductive strategy, likely influenced by the harsh alpine conditions in which U.torrefacta grows.[23]
Population structure
The population structure of U.torrefacta in the studied glacier foreland is highly skewed towards smaller individuals. This skewed size distribution indicates ongoing recruitment and colonisation in newly exposed areas, typical of primary succession in alpine environments. Most individuals are found in the smaller size classes, reflecting a population predominantly composed of younger thalli. Despite this, the species demonstrates resilience and the ability to establish itself successfully in newly available habitats, contributing to the stability and persistence of alpine lichen communities over time.[23]
Overall, the life history of U.torrefacta underscores its adaptation to the challenging conditions of alpine environments. The combination of slow growth, delayed reproduction, and continuous recruitment enables it to maintain a stable presence in dynamic and often harsh habitats, playing a role in the ecological succession following glacier retreat and other disturbances in high-altitude regions.[23]
Structural adaptations
Umbilicaria torrefacta has several structural adaptations that help it survive in its harsh coastal environment. The thallus structure, including the upper and lower cortex, algal layer, and medulla, varies significantly across different habitats. These structural variations allow the lichen to maintain a stable symbiotic relationship between the fungal and algal components, which is crucial for its survival. The fungal symbiont provides protection and a suitable microenvironment for the algal symbiont, aiding in water retention and shielding from excessive light.[16]
Research on U.torrefacta in the White Sea region has revealed its ability to adapt to various microclimatic conditions. The thallus structure of U.torrefacta shows a significant degree of plasticity, allowing it to grow in environments with fluctuating humidity and light levels. This adaptability is reflected in the varying thickness of its anatomical layers, such as the upper cortex, algal layer, medulla, and lower cortex. The lichen has a capacity to maintain a stable pigment composition, including chlorophylls and carotenoids, under conditions of different environmental stresses. These pigments play a crucial role in photosynthesis and protection against UV radiation, helping to ensure the lichen's survival in the exposed, often extreme conditions of its habitat.[24]
Uses
Tartan fabrics
Umbilicaria torrefacta holds historical significance as a natural dye in the Scottish Highlands. This lichen, commonly referred to as one of the "crotal" lichens, was traditionally used for dyeing wool and fabric. The dye produced from U.torrefacta yields a range of colours, including purplish-red and greyish-magenta hues, depending on the dyeing process and mordants used. The fermentation method involves soaking the lichen in an ammonia solution for several weeks to produce rich red and purple dyes. These colours were highly valued and often used in traditional Scottish tartans and textiles. The dyeing process using U.torrefacta and similar lichens was integral to the textile traditions of the Scottish Highlands. Lichen dyes were known for their vibrant and long-lasting colours, essential for creating the vivid hues seen in Highland dress.[25]
Related Research Articles
Hypotrachyna lueckingii is a species of corticolous (bark-dwelling), foliose lichen in the family Parmeliaceae. It is only known to occur at high elevations on the Cordillera de Talamanca in Costa Rica.
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.
Punctelia colombiana is a species of corticolous (bark-dwelling) and foliose (leafy) lichen in the family Parmeliaceae. It is found in South America.
Punctelia subpraesignis is a species of foliose lichen in the family Parmeliaceae. It occurs in Mexico, South America, and East Africa, where it grows on bark and on rocks. Major characteristics of the lichen that distinguish it from other Punctelia species include the C+ and KC+ rose spot tests of the medulla, ascospores that are smaller than 20 μm, and unciform (hooklike) conidia.
Punctelia hypoleucites, commonly known as the southwestern speckled shield lichen, is a species of foliose (leafy) lichen in the family Parmeliaceae. First formally described by Finnish botanist William Nylander as a species of Parmelia, it was transferred to the genus Punctelia in 1982. The lichen is found in Africa, North America, and South America, where it grows on the bark of both hardwood and coniferous trees. Its greenish-grey thallus is covered with tiny white pseudocyphellae – minute holes in the thallus surface that facilitate gas exchange. Some macroscopic features that help distinguish this species from other related members of the genus include the presence and the structure of the apothecia, the absence of asexual surface propagules, and the light brown color of the thallus undersurface. Chemically, the presence of lecanoric acid in the medulla and atranorin in the cortex help distinguish it from lookalikes.
Remototrachyna sipmaniana is a species of saxicolous (rock-dwelling), foliose lichen in the family Parmeliaceae. It is only known to occur in Bolivia, where it grows on boulders in Yungas mountain cloud forests.
Umbilicaria maculata is a species of saxicolous (rock-dwelling) umbilicate lichen in the family Umbilicariaceae. It is found in high-elevation alpine locations in Poland and France.
Solorina crocea, commonly known as the orange chocolate chip lichen, is a species of terricolous (ground-dwelling) and foliose (leafy) lichen in the family Peltigeraceae. The lichen, which was first formally described by Carl Linnaeus in 1753, has an arctic–alpine and circumpolar distribution and occurs in Asia, Europe, North America, and New Zealand. It generally grows on the bare ground in sandy soils, often in moist soil near snow patches or seepage areas. Although several forms and varieties of the lichen have been proposed in its history, these are not considered to have any independent taxonomic significance.
Umbilicaria muhlenbergii, commonly known as plated rock tripe, is a species of saxicolous (rock-dwelling, umbilicate lichen in the family Umbilicariaceae.
Parmotrema upretii is a species of saxicolous (rock-dwelling), foliose lichen in the family Parmeliaceae. Found in India, it was described as new to science in 2003 by Pradeep Divakar. The type specimen was collected near Banjar in the Kullu district of Himachal Pradesh, India at an altitude of 1,700 m (5,600 ft), where it was found growing on rock. The species epithet honours Indian lichenologist Dalip Kumar Upreti, who collected the type specimen.
Fuscopannaria rugosa is a species of corticolous (bark-dwelling), lichen in the family Pannariaceae. It is found in Hubei and Guanxi in China, where it grows in mountainous forests. Fuscopannaria rugosa is identifiable by its foliose-squamulose thallus, which has longitudinal wrinkles on the upper surface. It also has a distinct hypothallus, a relatively thick algal layer, and a cortex made up of thick-walled cells in both the thalline and apothecial structures. It produces simple, hyaline ascospores that have a smooth, pointed tip at their apex.
Opegrapha ramisorediata is a rare species of corticolous (bark-dwelling), crustose lichen in the family Opegraphaceae. Known to occur only in northeastern Brazil, it was described as a new species in 2017. It is characterised by a thin, pale greenish-mauve thallus.
Umbilicaria murihikuana is a rare species of saxicolous (rock-dwelling) lichen in the family Umbilicariaceae. It is endemic to New Zealand, where it occurs in mountainous, high-rainfall areas of Otago and Southland. It grows on exposed rocks and boulders at altitudes between 1,000 and 1,500 m, in subalpine to alpine habitats.
Lecidea lygommella is a species of saxicolous (rock-dwelling), crustose lichen in the family Lecideaceae. It spreads up to 7 cm wide with a thin thallus varying in colour from whitish and pale grey to rusty red-brown, featuring areolate surfaces with irregularly shaped areoles. Its fruiting bodies range from slightly embedded to sitting atop the thallus and black, flat to slightly convex apothecial discs. Unlike its lookalike Lecidea lygomma, L. lygommella does not produce any secondary chemicals. It is found in New South Wales and Victoria, Australia, where it grows on rocks in alpine areas.
Awasthia is a monotypic fungal genus in the family Physciaceae. It contains the single species Awasthia melanotricha, a foliose lichen found in the Nepal Himalayas.
Umbilicaria angulata, commonly known as the asterisk rocktripe, is a species of saxicolous (rock-dwelling), foliose lichen in the family Umbilicariaceae. It is found in northwestern North America and east Eurasia, where it grows on acidic rock.
Umbilicaria semitensis, commonly known as Yosemite rock tripe, is a species of foliose lichen in the family Umbilicariaceae. It occurs in the western regions of northern North America, from southern California to southern Oregon.
Umbilicaria isidiosa is a species of foliose lichen belonging to the family Umbilicariaceae. It is endemic to Bolivia, where it occurs in high-altitude regions of the Bolivian Andes. It is distinguished by its thallus, which has an upper surface ranging from ashy brown to mouse grey, featuring a frosty texture that varies from smooth to slightly rough. This surface is adorned with numerous isidia, ranging from spherical to richly branched, primarily concentrated along the margins. The lower surface is dark, transitioning from smooth to rough in texture, and sparsely covered with dark rhizines.
Umbilicaria nodulospora is a species of foliose lichen in the family Umbilicariaceae, discovered on steep rock faces of old lava flows in California and Oregon, USA. This species is distinguished by the unique shape of its ascospores and its DNA sequence, which does not closely relate to any known species within its family.
Umbilicaria orientalis is a species of foliose lichen belonging to the family Umbilicariaceae. It is recognized by its distinctive morphological features and unique molecular characteristics that distinguish it from closely related species such as Umbilicaria trabeculata. This lichen is primarily found across a range of localities in East Asia, extending from the Russian Far East to South Siberia, Mongolia, and regions in China including Hebei and Tibet.
1 2 3 4 5 Hestmark, Geir (2017). "Lectotypification of Umbilicaria torrefacta (Lightf.) Schrad". The Lichenologist. 49 (2): 167–169. doi:10.1017/S0024282916000682.
↑ Schrader, Heinrich Adolf (1794). Spicilegium Florae Germanicae. Pars Prior[Collection of German Flora. First Part] (in Latin). Hannover: Impensis Christiania Ritscheri. p.104.
1 2 3 4 McMullin, R. Troy (2023). Lichens. The Macrolichens of Ontario and the Great Lakes Region of the United States. Firefly Books. p.519. ISBN978-0-228-10369-1.
1 2 Llano, George Albert (1950). A Monograph of the Lichen Family Umbilicariaceae in the Western Hemisphere. Naval research logistics quarterly. Washington, D.C.: Office of Naval Research. Department of the Navy. pp.163–165.
1 2 3 4 Sonina, Anzhella V.; Tsunskaya, Anna A. (2016). "Structural and functional adaptations of epilithic lichens of Umbilicaria genus in the White Sea coastal conditions". Czech Polar Reports. 6 (2): 169–179. doi:10.5817/CPR2016-2-15.
↑ Grierson, Su; Duff, David G.; Sinclair, Roy S. (1985). "Natural dyes of the Scottish Highlands". Textile History. 16 (1): 23–43. doi:10.1179/004049685793701223.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
