A lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. Lichens have properties different from those of their component organisms. They come in many colors, sizes, and forms and are sometimes plant-like, but are not plants. They may have tiny, leafless branches (fruticose); flat leaf-like structures (foliose); grow crust-like, adhering tightly to a surface (substrate) like a thick coat of paint (crustose); have a powder-like appearance (leprose); or other growth forms.
Peltigera is a genus of approximately 100 species of foliose lichens in the family Peltigeraceae. Commonly known as the dog or pelt lichens, species of Peltigera are often terricolous, but can also occur on moss, trees, rocks, and many other substrates in many parts of the world.
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.
Peltigerales is an order of lichen-forming fungi belonging to the class Lecanoromycetes in the division Ascomycota. The taxonomy of the group has seen numerous changes; it was formerly often treated as a suborder of the order Lecanorales. It contains two suborders, eight families and about 45 genera such as Lobaria and Peltigera.
An isidium is a vegetative reproductive structure present in some lichens. Isidia are outgrowths of the thallus surface, and are corticated, usually with a columnar structure, and consisting of both fungal hyphae and algal cells. They are fragile structures and may break off and be distributed by wind, animals, and splashing raindrops. In terms of structure, isidia may be described as warty, cylindrical, clavate (club-shaped), scale-like, coralloid (coral-shaped), simple, or branched.
Nephroma is a genus of medium to large foliose lichens. The genus has a widespread distribution. They are sometimes called kidney lichens, named after the characteristic kidney-shaped apothecia that they produce on the lower surface of their lobe tips, which often curl upwards and thus are visible from above. Sterile specimens that do not have apothecia can look somewhat like Melanelia, Peltigera, Platismatia, or Asahinea. Most species grow either on mossy ground or rocks, or on trees.
Peltigera aphthosa is a species of lichen known by the common names green dog lichen, leafy lichen, felt lichen, and common freckle pelt. It has a circumpolar distribution, occurring throughout the Arctic, boreal, and temperate regions of the Northern Hemisphere.
Lichens of the Sierra Nevada have been little studied. A lichen is a composite organism consisting of a fungus and a photosynthetic partner growing together in a symbiotic relationship.
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. 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 helpful symbiotic relationship of green algae and/or blue-green algae (cyanobacteria) living among filaments of a fungus, forming lichen.
Some types of lichen are able to fix nitrogen from the atmosphere. This process relies on the presence of cyanobacteria as a partner species within the lichen. The ability to fix nitrogen enables lichen to live in nutrient-poor environments. Lichen can also extract nitrogen from the rocks on which they grow.
Peltigera vainioi is a species of lichen in the family Peltigeraceae. It is found in high-elevation locations in South America. It is a somewhat unusual species in its genus, characterized by a single holdfast that attaches to its substrate, and pores in its cortex.
Peltigera canina, commonly known as the dog lichen, is a widely distributed species of foliose lichen in the family Peltigeraceae. It was originally described by Carl Linnaeus in his 1753 work Species Plantarum. German botanist Carl Ludwig Willdenow transferred it to the genus Peltigera in 1787. This species is currently undergoing research as it is likely multiple species under one united name.
Peltigera gowardii, or western waterfan, is an aquatic lichen found only in mountain streams of Western North America. It is the largest aquatic lichen in the Pacific Northwest.
Peltigera papuana is a lichenized fungus in the family Peltigeraceae. It was described in 2009 from Madang Province of Papua New Guinea, from which it obtained its specific epithet. Genetic analysis of both the mycobiont and the photobiont, which is a Nostoc cyanobacterium, suggests that the evolutionary origin of Pelitgera papuana is from an ancient dispersal event from South America, although this remains inconclusive.
Sinuicella is a fungal genus in the family Peltigeraceae. It is a monotypic genus, containing the single species Sinuicella denisonii. Both the genus and species were described as new to science in 2021 by Daphne Stone, Bruce McCune, and Jolanta Miądlikowska. The type specimen was collected by the first author from Polk County, Oregon (USA), where it was found growing on the soil. It is only known to occur in the region of the type locality. The lichen has a minute fruticose (bushy) grey to almost black thallus. The photobiont partner is a member of the cyanobacterial genus Nostoc. The genus name Sinuicella refers to the cortical cells with curved protrusions in their outlines, somewhat resembling jigsaw puzzle pieces. The specific epithet denisonii honours mycologist William C. Denison, who was, according to the authors, "a pioneer in the use of lichens to monitor air quality in the United States."
Peltigera rufescens, commonly known as the field dog lichen, is a species of terricolous (ground-dwelling), foliose lichen in the family Peltigeraceae. The common and widespread species has a cosmopolitan distribution.
Peltigera shennongjiana is a species of terricolous (ground-dwelling), foliose lichen in the family Peltigeraceae. Found in Central China, it was formally described as a new species in 2016 by Liu-Fu Han and Shou-Yu Guo. The type specimen was collected from Laojunshan Mountain in the Shennongjia Forestry District at an altitude of 900 m (3,000 ft); here it was found growing on mosses over rocks and soil. The species epithet refers to the type locality.
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.
