Beginning in 1867, a lichen was understood as a symbiosis of an algae or cyanobacteria, living among filaments of multiple fungi species. In 2016, new research by T. Spribille et al. revealed a third partner, a yeast imbedded in the lichen cortex or "skin."
Xanthoria parietina is a foliose lichen in the family Teloschistaceae. It has wide distribution, and many common names such as common orange lichen, yellow scale, maritime sunburst lichen and shore lichen. It can be found near the shore on rocks or walls, and also on inland rocks, walls, or tree bark. It was chosen as a model organism for genomic sequencing by the US Department of Energy Joint Genome Institute (JGI).
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.
Trebouxia is a unicellular green alga. It is a photosynthetic organism that can exist in almost all habitats found in polar, tropical, and temperate regions. It can either exist in a symbiotic relationship with fungi in the form of lichen or it can survive independently as a free-living organism alone or in colonies. Trebouxia is the most common photobiont in extant lichens. It is a primary producer of marine, freshwater and terrestrial ecosystems. It uses carotenoids and chlorophyll a and b to harvest energy from the sun and provide nutrients to various animals and insects.
The Teloschistaceae are a large family of mostly lichen-forming fungi belonging to the class Lecanoromycetes in the division Ascomycota. The family has a cosmopolitan distribution, although its members occur predominantly in temperate regions. Most members are lichens that either live on rock or on bark, but about 40 species are lichenicolous – meaning they are non-lichenised fungi that live on other lichens. Many members of the Teloschistaceae are readily identifiable by their vibrant orange to yellow hue, a result of their frequent anthraquinone content. The presence of these anthraquinone pigments, which confer protection from ultraviolet light, enabled this group to expand from shaded forest habitats to harsher environmental conditions of sunny and arid ecosystems during the Late Cretaceous.
Buellia is a genus of mostly lichen-forming fungi in the family Caliciaceae. The fungi are usually part of a crustose lichen. In this case, the lichen species is given the same name as the fungus. But members may also grow as parasites on lichens (lichenicolous). The algae in the lichen is always a member of the genus Trebouxia.
Pilophorus acicularis, commonly known as the nail lichen or the devil's matchstick lichen, is a species of matchstick lichen in the family Cladoniaceae.
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.
Lichen anatomy and physiology is very different from the anatomy and physiology of the fungus and/or algae and/or cyanobacteria that make up the lichen when growing apart from the lichen, either naturally, or in culture. The fungal partner is called the mycobiont. The photosynthetic partner, algae or cyanobacteria, is called the photobiont. The body of a lichens that does not contain reproductive parts of the fungus is called the thallus. The thallus is different from those of either the fungus or alga growing separately. The fungus surrounds the algal cells, often enclosing them within complex fungal tissues unique to lichen associations. In many species the fungus penetrates the algal cell wall, forming penetration pegs or haustoria similar to those produced by pathogenic fungi. Lichens are capable of surviving extremely low levels of water content (poikilohydric). However, the re-configuration of membranes following a period of dehydration requires several minutes at least.
Symbiosis in lichens is the mutually beneficial symbiotic relationship of green algae and/or blue-green algae (cyanobacteria) living among filaments of a fungus, forming lichen.
Ramalina menziesii, the lace lichen or fishnet, is a pale yellowish-green to grayish-green fruticose lichen. It grows up to a meter long, hanging from bark and twigs in a distinctive net-like or lace-like pattern that is unlike any other lichen in North America. It becomes a deeper green when wet. Apothecia are lecanorine. Lace lichen is an important food source for deer in the Coast Range of California, and a source of nest material for birds. It is highly variable in its growth form, with branches sometimes so slender as to appear like strands, sometimes tiny, and sometimes large with broadly flattened branches.
Teuvoa is a genus of lichen-forming fungi in the family Megasporaceae. It was first classified by lichenologists Mohammad Sohrabi and Steven Leavitt in 2013, with Teuvoa uxoris asigned as the type species. This genus was delineated from the larger genus, Aspicilia, following a molecular phylogenetic analysis which revealed that the Aspicilia uxoris species group constituted a distinct lineage in the Megasporaceae. Initially containing three species, two additional species native to China were added in 2018. Teuvoa is characterised by its small ascospores and conidia, and the absence of secondary metabolites.
Wahlenbergiella tavaresiae is a species of saxicolous (rock-dwelling), crustose lichen in the family Verrucariaceae. Known from several locations in the San Francisco Bay area of the United States, it is a marine lichen that inhabits intertidal zones, and as such is immersed in seawater on a regular basis. Associated algal species include the red algae Hildenbrandia and Mastocarpus papillatus, and the brown algae Pelvetiopsis and Fucus. Petroderma maculiforme, a brown alga, is the photobiont partner in the lichen.
Xanthoria aureola, commonly known as the seaside sunburst lichen, is a lichenized species of fungus in the family Teloschistaceae and phylum Ascomycota. X. aureola can be recognized by its bright yellow-orange pigmentation and abundant strap-shaped lobes. It is usually found growing on exposed, nutrient-rich rocks in sunny, maritime habitats. It is largely restricted to European coasts, stretching from Portugal to Norway.
Anaptychia ciliaris, commonly known as the great ciliated lichen or eagle's claws, is a species of fruticose lichen in the family Physciaceae. It is predominantly found in Northern Europe, with its range extending to European Russia, the Caucasus, Central and Southern Europe, the Canary Islands, and some parts of Asia. First mentioned in botanical literature by Italian botanist Fabio Colonna in 1606, the species was formally described by Carl Linnaeus in 1753, who highlighted its unique physical characteristics such as its grey colour, its unusual leafy form with linear fringe-like segments, and the presence of hair-like structures. This lichen is adaptable in its choice of substrates, mostly growing on tree barks, and less commonly on rocks.
Trebouxia arboricola is a symbiotic species of green alga in the family Trebouxiaceae. Described as new to science in 1924, it is usually found in association with different species of lichen-forming fungi and has a broad global distribution.
Trebouxia gelatinosa is a common symbiotic species of green alga in the family Trebouxiaceae. Formally described as new to science in 1975, it is usually found in association with different species of lichen-forming fungi.
Gallowayella weberi is a species of corticolous and saxicolous, foliose lichen in the family Teloschistaceae. Found in the eastern United States, it is a small lichen with a smooth yellow to orange upper surface and a contrasting white lower surface.
Asterochloris is a genus of green algae in the family Trebouxiophyceae. It is a common photobiont in lichen, occurring in the thalli of more than 20 lichen genera worldwide. Asterochloris is distinguishable from the morphologically similar genus Trebouxia, primarily due to its deeply lobed chloroplast, the placement of the chloroplast along the cell's periphery before the initiation of zoospore or aplanospore formation, and its tendency to primarily reproduce asexually through the production of aplanospores.
Asterochloris italiana is a species of green alga in the family Trebouxiaceae. It was first formally described by the phycologist Patricia A. Archibald in 1975, as a species of Trebouxia. It was transferred to the genus Asterochloris in 2010.
