Lichenology

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Lichen Rhizocarpon geographicum on quartz.jpg
Lichen

Lichenology is the branch of mycology that studies the lichens, symbiotic organisms made up of an intimate symbiotic association of a microscopic alga (or a cyanobacterium) with a filamentous fungus. Lichens are chiefly characterized by this symbiosis.

Contents

Study of lichens draws knowledge from several disciplines: mycology, phycology, microbiology and botany. Scholars of lichenology are known as lichenologists. Study of lichens is conducted by both professional and amateur lichenologists.

Methods for species identification include reference to single-access keys on lichens. An example reference work is Lichens of North America (2001) by Irwin M. Brodo, Sylvia Sharnoff and Stephen Sharnoff and that book's 2016 expansion, Keys to Lichens of North America: Revised and Expanded by the same three authors joined by Susan Laurie-Bourque. [1]

A chemical spot test can be used to detect the presence of certain lichen products which can be characteristic of a given lichen species. Some components of certain lichens may also fluoresce under ultraviolet light, providing another form of lichen identification test.

Lichenologists may also study the growth and growth rate of lichens, lichenometry, the role of lichens in nutrient cycling, the ecological role of lichens in biological soil crusts, the morphology of lichens, their anatomy and physiology, and ethnolichenology topics including the study of edible lichens. As with any other field of study, lichenology has its own set of rules for taxonomic nomenclature and its own set of other terminology.

History

The beginnings

Lichens as a group have received less attention in classical treatises on botany than other groups although the relationship between humans and some species has been documented from early times. Several species have appeared in the works of Dioscorides, Pliny the Elder and Theophrastus although the studies are not very deep. During the first centuries of the modern age they were usually put forward as examples of spontaneous generation and their reproductive mechanisms were totally ignored. [2] For centuries naturalists had included lichens in diverse groups until in the early 18th century a French researcher Joseph Pitton de Tournefort in his Institutiones Rei Herbariae grouped them into their own genus. He adopted the Latin term lichen, which had already been used by Pliny who had imported it from Theophrastus but up until then this term had not been widely employed. [3] The original meaning of the Greek word λειχήν (leichen) was moss that in its turn derives from the Greek verb λείχω (liekho) to suck because of the great ability of these organisms to absorb water. In its original use the term signified mosses, liverworts as well as lichens. Some forty years later Dillenius in his Historia Muscorum made the first division of the group created by Tournefort separating the sub-families Usnea, Coralloides [lower-alpha 1] and Lichens in response to the morphological characteristics of the lichen thallus. [5]

After the revolution in taxonomy brought in by Linnaeus and his new system of classification lichens are retained in the Plant Kingdom forming a single group Lichen with eight divisions within the group according to the morphology of the thallus. [6] The taxonomy of lichens was first intensively investigated by the Swedish botanist Erik Acharius (1757–1819), who is therefore sometimes named the "father of lichenology". Acharius was a student of Carl Linnaeus. Some of his more important works on the subject, which marked the beginning of lichenology as a discipline, are:

Lichen on rocks Flechte auf Fels.jpg
Lichen on rocks
Oakmoss (Evernia prunastri) Lichen foliace2..JPG
Oakmoss (Evernia prunastri)

Later lichenologists include the American scientists Vernon Ahmadjian and Edward Tuckerman and the Russian evolutionary biologist Konstantin Merezhkovsky, as well as amateurs such as Louisa Collings.

Over the years research shed new light into the nature of these organisms still classified as plants. A controversial issue surrounding lichens since the early 19th century is their reproduction. In these years a group of researchers faithful to the tenets of Linnaeus considered that lichens reproduced sexually and had sexual reproductive organs, as in other plants, independent of whether asexual reproduction also occurred. Other researchers only considered asexual reproduction by means of Propagules. [7]

19th century

Against this background appeared the Swedish botanist Erik Acharius disciple of Linnaeus, who is today considered the father of lichenology, starting the taxonomy of lichens with his pioneering study of Swedish lichens in Lichenographiae Suecicae Prodromus of 1798 or in his Synopsis Methodica Lichenum, Sistens omnes hujus Ordinis Naturalis of 1814. [8] These studies and classifications are the cornerstone of subsequent investigations. In these early years of structuring the new discipline various works of outstanding scientific importance appeared such as Lichenographia Europaea Reformata published in 1831 by Elias Fries or Enumeratio Critico Lichenum Europaeorum 1850 by Ludwig Schaerer [9] in Germany. [10]

Erik Acharius (1757-1819), Swedish botanist, the father of lichenology Erik Acharius.jpg
Erik Acharius (1757–1819), Swedish botanist, the father of lichenology

But these works suffer from being superficial and mere lists of species without further physiological studies. [11] It took until the middle of the 19th century for research to catch up using biochemical and physiological methods. In Germany Hermann Itzigsohn  [ de ] [12] and Johann Bayrhoffer, [13] in France Edmond Tulasne and Camille Montagne, in Russia Fedor Buhse, [14] in England William Allport Leighton and in the United States Edward Tuckerman began to publish works of great scientific importance.

Scientific publications settled many unknown facts about lichens. In the French publication Annales des Sciences Naturelles in an article of 1852 "Memorie pour servir a l'Histoire des Lichens Organographique et Physiologique" by Edmond Tulasne, the reproductive organs or apothecia of lichens was identified. [15] [16]

These new discoveries were becoming increasingly contradictory for scientists. The apothecium reproductive organ being unique to fungi but absent in other photosynthetic organisms. With improvements in microscopy, algae were identified in the lichen structure, which heightened the contradictions. At first the presence of algae was taken as being due to contamination due to collection of samples in damp conditions and they were not considered as being in a symbiotic relation with the fungal part of the thallus. That the algae continued to multiply showed that they were not mere contaminants.

It was Anton de Bary a German mycologist who specialised in phytopathology who first suggested in 1865 that lichens were merely the result of parasitism of various fungi of the ascomycetes group by nostoc type algae and others. Successive studies such as those carried out by Andrei Famintsyn and Baranetzky [17] in 1867 showed no dependence of the algal component upon the lichen thallus and that the algal component could live independently of the thallus. [18] It was in 1869 that Simon Schwendener demonstrated that all lichens were the result of fungal attack on the cells of algal cells and that all these algae also exist free in nature. This researcher was the first to recognise the dual nature of lichens as a result of the capture of the algal component by the fungal component. [19] In 1873 Jean-Baptiste Edouard Bornet concluded form studying many different lichen species that the relationship between fungi and algae was purely symbiotic. It was also established that algae could associate with many different fungi to form different lichen phenotypes.

French botanist (Jean-Baptiste) Edouard Bornet (1828-1911) Edouard Bornet.jpg
French botanist (Jean-Baptiste) Édouard Bornet (1828–1911)

20th century

In 1909 the Russian lichenologist Konstantin Mereschkowski presented a research paper "The Theory of two Plasms as the basis of Symbiogenesis, A new study on the Origin of Organisms", which aims to explain a new theory of Symbiogenesis by lichens and other organisms as evidenced by his earlier work "Nature and Origin of Chromatophores in the Plant Kingdom". These new ideas can be studied today under the title of the Theory of Endosymbiosis. [20]

Despite the above studies the dual nature of lichens remained no more than a theory until in 1939 the Swiss researcher Eugen A Thomas [21] was able to reproduce in the laboratory the phenotype of the lichen Cladonia pyxidata [22] by combining its two identified components.

During the 20th century botany and mycology were still attempting to solve the two main problems surrounding lichens. On the one hand the definition of lichens and the relationship between the two symbionts and the taxonomic position of these organisms within the plant and fungal kingdoms. There appeared numerous renowned researchers within the field of lichenology such as Henry Nicollon des Abbayes, William Alfred Weber, Antonina Georgievna Borissova, Irwin M. Brodo, and George Albert Llano.

Lichenology has found applications beyond biology itself in the field of geology in a technique known as lichenometry where the age of an exposed surface can be found by studying the age of lichens growing on them. Age dating in this way can be absolute or relative because the growth of these organisms can be arrested under various conditions. The technique provides an average age of the older individual lichens providing a minimum age of the medium being studied. [23] Lichenometry relies upon the fact that the maximum diameter of the largest thallus of an epilithic lichen growing on a substrate is directly proportional to the time from first exposure of the area to the environment as seen in studies by Roland Beschel [24] in 1950 and is especially useful in areas exposed for less than 1000 years. Growth is greatest in the first 20 to 100 years with 15–50 mm growth per year and less in the following years with average growth of 2–4 mm per year. [25]

The difficulty of giving a definition applicable to every known lichen has been debated since lichenologists first recognised the dual nature of lichens. In 1982 the International Association for Lichenology convened a meeting to adopt a single definition of lichen drawing on the proposals of a committee. The chairman of this committee was the renowned researcher Vernon Ahmadjian. The definition finally adopted was that lichen could be considered as the association between a fungus and a photosynthetic symbiont resulting in a thallus of specific structure. [26]

Such a simple a priori definition soon brought criticism from various lichenologists and there soon emerged reviews and suggestions for amendments. For example, David L. Hawksworth considered the definition imperfect because it is impossible to determine which one thallus is of a specific structure since thalli changed depending upon the substrate and conditions in which they developed. This researcher represents one of the main trends among lichenologists who consider it impossible to give a single definition to lichens since they are a unique type of organism. [26]

Today studies in lichenology are not restricted to the description and taxonomy of lichens but have application in various scientific fields. Especially important are studies on environmental quality that are made through the interaction of lichens with their environment. Lichen is extremely sensitive to various air pollutants, especially to sulphur dioxide, which causes acid rain and prevents water absorption.

K S Merezhkovsky Russian Lichenologist (1855-1921) Merezhkovsky K S.jpg
K S Merezhkovsky Russian Lichenologist (1855–1921)

Lichens in pharmacology

Although several species of lichen have been used in traditional medicine it was not until the early 20th century that modern science became interested in them. The discovery of various substances with antibacterial action in lichen thalli was essential for scientists to become aware of the possible importance of these organisms to medicine. [27] From the 1940s there appeared various works by the noted microbiologist Rufus Paul Burkholder who demonstrated antibacterial action of lichens of the genus Usnea against Bacillus subtilis and Sarcina lutea . [28] Studies showed that the substance that inhibited growth of bacteria was usnic acid. Something similar occurred with the substance Ramelina synthesised by the lichen Ramalina reticulata , [29] nevertheless, these substances proved ineffective against Gram negative bacteria such as Escherichia coli and Pseudomonas . With these investigations the number of antibacterial substances and possible drug targets known to be produced by lichens increased ergosterol, usnic acid etc. [30]

Interest in the potential of substances synthesised by lichens increased with the end of World War II along with the growing interest in all antibiotic substances. In 1947 antibacterial action was identified in extracts of Cetraria islandica and the compounds identified as responsible for bacterial inhibition were shown to be d-protolichosteric acid and d-1-usnic acid. [31] Further investigations have identified novel antibacterial substances, Alectosarmentin [32] or Atranorin. [33]

Antibacterial action of substances produced by lichens is related to their ability to disrupt bacterial proteins with a subsequent loss of bacterial metabolic capacity. This is possible due to the action of lichen phenolics such as usnic acid derivatives. [34]

From the 1950s the lichen product usnic acid was the object of most antitumour research. These studies revealed some in vitro antitumour activity by substances identified in two common lichens Peltigera leucophlebia and Collema flaccidum . [35]

Recent work in the field of applied biochemistry has shown some antiviral activity with some lichen substances. In 1989 K Hirabayashi [36] presented his investigations on inhibitory lichen polysaccharides in HIV infection. [37]

Bibliography

Notable lichenologists

Lichen collections

See also

Footnotes

  1. ↑ "mostly Clavarieae", according to Druce. [4]

Related Research Articles

<span class="mw-page-title-main">Erik Acharius</span> Swedish botanist (1757-1819)

Erik Acharius was a Swedish botanist who pioneered the taxonomy of lichens and is known as the "father of lichenology". Acharius was famously the last pupil of Carl Linnaeus.

William Alfred Weber was an American botanist and lichenologist. He was Professor Emeritus at the University of Colorado at Boulder and former curator of the University of Colorado Museum Herbarium.

Vernon Ahmadjian was a distinguished professor at Clark University in Worcester, Massachusetts. He specialized in the symbiosis of lichens, and wrote several books and numerous publications on the subject.

Irwin M. Brodo is an emeritus scientist at the Canadian Museum of Nature, in Ottawa, Ontario, Canada. He is an authority on the identification and biology of lichens. Irwin Brodo was honored in 1994 with an Acharius Medal presented to him by the International Association for Lichenology.

<i>Vulpicida</i> Genus of lichen

Vulpicida is a genus of lichenized fungi in the family Parmeliaceae. Circumscribed in 1993 to contain species formerly placed in Cetraria, the genus is widespread in Arctic to northern temperate regions, and contains six species. The genus is characterized by the presence of the secondary metabolites pulvinic acid and vulpinic acid, compounds that when combined with usnic acid, give the species their characteristic yellow and green colors.

<span class="mw-page-title-main">American Bryological and Lichenological Society</span> Botanical organization

The American Bryological and Lichenological Society is an organization devoted to the scientific study of all aspects of the biology of bryophytes and lichen-forming fungi and is one of the nation's oldest botanical organizations. It was originally known as the Sullivant Moss Society, named after William Starling Sullivant. The Society publishes a quarterly journal distributed worldwide, The Bryologist, which includes articles on all aspects of the biology of mosses, hornworts, liverworts and lichens. The Society also publishes the quarterly journal Evansia, which is intended for both amateurs and professionals in bryology and lichenology and is focused on North America.

<i>Cryptothecia rubrocincta</i> Species of fungus

Cryptothecia rubrocincta is a species of lichen in the fungal family Arthoniaceae. The species is distributed in subtropical and tropical locations throughout the southeastern United States, as well as Central and South America, and has been collected infrequently in a few locales in Africa. The body of the lichen forms continuous, circular crust-like patches on dead wood, readily recognizable by the prominent red pigment. The older, central region is covered with red, spherical to cylindrical granules. Moving outwards from the center, zones of color may be distinguished, the first gray-green, the second white, and finally a bright red cottony rim. The red and green colors of this unmistakable woodland lichen give the appearance of a Christmas wreath, suggestive of its common North American name, the Christmas (wreath) lichen. The red pigment, called chiodectonic acid, is one of several chemicals the lichen produces to help tolerate inhospitable growing conditions.

<span class="mw-page-title-main">William Louis Culberson</span> American lichenologist

William Louis "Bill" Culberson was an American lichenologist.

A spot test in lichenology is a spot analysis used to help identify lichens. It is performed by placing a drop of a chemical reagent on different parts of the lichen and noting the colour change associated with application of the chemical. The tests are routinely encountered in dichotomous keys for lichen species, and they take advantage of the wide array of lichen products produced by lichens and their uniqueness among taxa. As such, spot tests reveal the presence or absence of chemicals in various parts of a lichen. They were first proposed as a method to help identify species by the Finnish lichenologist William Nylander in 1866.

The International Association for Lichenology (IAL) is an organisation that encourages the understanding of lichens and lichenology, and promotes their study and conservation worldwide. It unites lichenologists across the globe, as well as national and regional organisations into one group. It is affiliated to the International Union of Biological Sciences (IUBS). The IAL organises field courses and excursions, as well as symposia which are the biggest events in lichenology on the international level. The 8th International Symposium will be held in Helsinki, Finland, in August 2016.

<span class="mw-page-title-main">Elke Mackenzie</span> British polar explorer and lichenologist (1911–1990)

Elke Mackenzie, born Ivan Mackenzie Lamb, was a British polar explorer and botanist who specialised in the field of lichenology. Beginning her education in Edinburgh, Scotland, Mackenzie later pursued botany at Edinburgh University, earning a Bachelor of Science degree in 1933 and a Doctor of Science in 1942. In the two years she was involved in Operation Tabarin, a covert World War II mission to Antarctica, she identified and documented many lichen species, several of them previously unknown to science.

Antonín (Toni) Vězda was a Czech lichenologist. After completing a university education that was postponed by World War II, Vězda taught botany at the Czech University of Life Sciences. In 1958, he was dismissed from his university position as a result of the restrictions placed on academic freedoms by the communist regime in power. He eventually was hired as a lichen researcher by the Czechoslovak Academy of Sciences, who allowed him to work from his apartment, which served also as an office and herbarium.

<span class="mw-page-title-main">Gunnar Degelius</span> Swedish lichenologist

Gunnar Bror Fritiof Degelius was a Swedish lichenologist. Between the publications of his first and final scientific papers, Degelius had a 70-year-long research career. While he was best known for his expertise on the lichen genus Collema, he also wrote important papers on lichen biology and ecology, floristic studies of the Nordic countries and various other areas around the world, and lichen succession. Degelius described 124 new taxa, and published about 130 scientific papers. In 1992 he was one of the first to be awarded the Acharius Medal for his lifetime contributions to lichenology. Fifteen species and three genera have been named in honour of Degelius.

<i>Pulchrocladia retipora</i> Species of fruticose lichen

Pulchrocladia retipora, commonly known as the coral lichen, is a species of fruticose lichen in the family Cladoniaceae. Found predominantly in Australasia, its habitats range from the Australian Capital Territory to New Zealand's North and South Islands, and even the Pacific region of New Caledonia, where it grows in coastal and alpine heathlands. The lichen features coral-like branches and subbranches with numerous intricate, netlike perforations. It is known by multiple names, with some sources referring to it by its synonym Cladia retipora, or the common name lace lichen.

<span class="mw-page-title-main">Siegfried Huneck</span> German chemist and lichenologist (1928–2011)

Siegfried Huneck was a German chemist and lichenologist. Much of his scientific career was hampered by the political situation in the former German Democratic Republic. He rejected pursuing a career in academia, and instead ended up working at the Leibniz Institute of Plant Biochemistry, a public research institute, from 1969 until his retirement in 1993. Despite his relative isolation and restricted freedoms in East Germany, Huneck had numerous professional contacts both in Germany and abroad, and was a highly published scholar. Many of his more than 400 scientific publications dealt with the chemistry of lichen products. He was awarded the Acharius Medal for lifetime achievements in lichenology in 1996.

<span class="mw-page-title-main">Ludwig Schaerer</span> Swiss clergyman and lichenologist

Ludwig Emanuel Schaerer was a Swiss pastor and lichenologist. Interested in natural history from a young age, Schaerer trained as a teacher and studied theology in Bern. During his career as a teacher, orphanage director, and pastor, he researched extensively and maintained correspondence with foreign botanists interested in cryptogams. Schaerer was best known for his multi-volume work Lichenum Helveticorum Spicilegium, published in 12 parts from 1823 to 1842. This series catalogued and described the lichens of Switzerland, particularly those in the Alps, where he often went on collecting excursions. In another series, he compiled and distributed dried herbarium specimens acquired from his collections. Several lichen taxa have been named in honour of Schaerer.

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

The following outline provides an overview of and topical guide to lichens.

<i>Solorina crocea</i> Species of lichen

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.

<i>Chrysothrix chlorina</i> Species of lichen

Chrysothrix chlorina, the sulphur dust lichen, is a species of leprose (powdery) crustose lichen in the family Chrysotrichaceae. Originally described scientifically by the Swedish lichenologist Erik Acharius over 200 years ago, it has been shuffled to many different genera in its taxonomic history before finally being transferred to Chrysothrix in 1981. The lichen has a circumboreal distribution, meaning it occurs in northern boreal regions across the planet. It is typically saxicolous (rock-dwelling), particularly on the underside of rock overhangs, but has in rare instances been recorded growing on bark and various other surfaces.

References

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  2. ↑ Lauder Lindsay, William (1856). A Popular History of British Lichens p. 22
  3. ↑ Lauder Lindsay, William (1856). A Popular History of British Lichens p. 23
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  6. ↑ Lauder Lindsay, William (1856). A Popular History of British Lichens. p. 24.
  7. ↑ Lauder Lindsay, William. A Popular History of British Lichens. p. 25.
  8. ↑ Acharius, Erik (1814). Synopsis Methodica Lichenum: Systens omnes hujus ordinis naturalis detectas[Synopsis of lichen Methods, systems of this natural order detected] (in Latin). Svanborg.
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  26. 1 2 David L. Hawksworth (1989) "Interactions Fungus and Alga in Lichen Symbiosis liquenoides" Annals of the Botanical Garden of Madrid (46).
  27. ↑ http://lichens.science.oregonstate.edu/antibiotics/lichen_antibiotics.htm Mike Crockett, Stacie Kageyama, Delfina Homen, Carrie Lewis, Jane Osborn, Logan Sander (2003). "Antibacterial Properties of four Pacific North West Lichens".
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  31. ↑ Bustinza, Francisco (1951) "Contribution to the Study of Antibacterial Activity in Cetraria islandica". Annals of the Botanical Garden of Madrid (10) ISSN pp. 144–149.
  32. ↑ Gollapudi, S. R.; Telikepalli, H; Jampani, H. B.; Mirhom, Y. W.; Drake, S. D.; Bhattiprolu, K. R.; Vander Velde, D; Mitscher, L. A. (1994). "Alectosarmentin, a new antimicrobial dibenzofuranoid lactol from the lichen, Alectoria sarmentosa". Journal of Natural Products. 57 (7): 934–8. doi:10.1021/np50109a009. PMID   7964789.
  33. ↑ Edwards, Howell G.M.; Newton, Emma M.; Wynn-Williams, David D. (2003). "Molecular structural studies of lichen substances II: Atranorin, gyrophoric acid, fumarprotocetraric acid, rhizocarpic acid, calycin, pulvinic dilactone and usnic acid". Journal of Molecular Structure. 651–653: 27–37. Bibcode:2003JMoSt.651...27E. doi:10.1016/S0022-2860(02)00626-9.
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  37. ↑ Francisco Javier Toledo Marante, Ana Garcia Costellano, Francisco Leon Oyola and Jaime Bermejo Barrera "Ecologia Quimica en Hongos y Liquenes" (Spa) Columbian Academy of Science 28 ISSN 0370-3908 pp. 509–528
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