''Buellia'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of mostly

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

-forming

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

in the family

Caliciaceae The Caliciaceae are a family (taxonomy), family of mostly lichen-forming fungus, fungi belonging to the class (taxonomy), class Lecanoromycetes in the division (mycology), division Ascomycota. Although the family has had its classification chan ...

. The fungi are usually part of a

crustose lichen Crustose lichens are lichens that form a crust which strongly adheres to the Substrate (biology), substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. The basic structure of crustose lichen ...

. In this case, the lichen

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

is given the same name as the fungus. But members may also grow as

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s on lichens ( lichenicolous). The

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

in the lichen (the

photobiont A lichen ( , ) is a hybrid colony of algae or cyanobacteria living symbiotically among filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualistic relationship.

partner) is always a member of the genus ''

Trebouxia ''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.Erokhina, L. G., Shatilovich, A. V., Kaminskaya, O. P., & Gilichinskii, D. A. (2004 ...

''. Lichens in the genus are commonly called disc lichens, or button lichens.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, The genus has a widespread distribution and contains almost 1000 species. Genetic studies indicate that the genus ''

Amandinea ''Amandinea'' is a genus of lichenized fungi in the family Caliciaceae. Genetic studies indicates that the genus ''Amandinea'' and ''Buellia'' are the same,Scheidegger, C. 2009. Amandinea Choisy ex Scheid. & H. Mayrhofer (1993). In: C. W. Smith ...

'' and ''Buellia'' may be the same, although this is not widely accepted.Amandinea punctata in the Joshua Tree National Park (California, U.S.A.) Map collection: Kerry Knudsen, Kocourková Jana; Czech University of Life Sciences Prague, Faculty of Environmental Sciences, Department of Ecology, Czech Republic; 2012 The genus ''Buellia'' was described by Italian botanist Gioseppe De Notaris in 1846 and named after his friend, Esperanzo Buelli.

Description

Genus ''Buellia'' consists of lichens that are either lichenised or occasionally lichenicolous. This means they typically form a symbiotic relationship with a photosynthetic partner, or in some cases,

parasitise Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

other lichens. Most ''Buellia'' species are independent, forming their own visible

thallus Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...

(lichen body), but some start as parasites and eventually develop independent thalli. The thallus of ''Buellia'' species is

crustose Crustose is a Habit (biology), habit of some types of algae and lichens in which the organism grows tightly appressed to a substrate, forming a biological layer. ''Crustose'' adheres very closely to the Substrate (biology), substrates at all poin ...

, meaning it forms a crust-like layer. Its appearance can range from continuous to patchy, and it may be cracked or broken into small, tile-like segments (). In some cases, the thallus may develop into small scales or . Often, there is a , which is a preliminary growth stage that typically appears dark and may form a thin outline or a more extensive network between the . The surface of the thallus can be colourless or various shades of brown, yellow, or green, and it may be smooth, rough, or covered in a fine powder (). The margins of the thallus can be clearly defined or blend seamlessly into the substrate. The primary photobiont (symbiotic partner conducting photosynthesis) in ''Buellia'' is usually a species of ''

''. The

medulla Medulla (Latin for "marrow") or medullary may refer to: Science * Medulla oblongata, a part of the brain stem * Renal medulla, a part of the kidney * Adrenal medulla, a part of the adrenal gland * Medulla of ovary, a stroma in the center of the ...

, or inner tissue, is typically white but may contain yellow or orange

pigments A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

Calcium oxalate Calcium oxalate (in archaic terminology, oxalate of lime) is a calcium salt of oxalic acid with the chemical formula or . It forms hydrates , where ''n'' varies from 1 to 3. Anhydrous and all hydrated forms are colorless or white. The monohydr ...

crystals, which are colourless and needle-shaped, are often present in the medulla.

Apothecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...

, the reproductive structures where spores are formed, are common in ''Buellia''. They can be flat, slightly concave, or convex, and are usually black or dark brown. The margin of the apothecium can vary in appearance, sometimes containing remnants of the thallus or being edged with thallus material. The

hymenium The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in oth ...

(spore-producing layer) is clear but may contain oil droplets, and the

paraphyses Paraphyses are erect sterile filament-like support structures occurring among the reproductive apparatuses of fungi, ferns, bryophytes and some thallophytes. The singular form of the word is paraphysis. In certain fungi, they are part of the f ...

(filamentous structures) often have a distinct pigment cap, contributing to the colouration of the (top layer of the hymenium). The spores of ''Buellia'' are initially clear, turning olive gray and eventually dark brown, although in some species, they remain clear. They can have one or several partitions (septa) and come in various shapes, often being straight but sometimes curved. The development of the spores involves forming the septum before or after the development of pigmentation and wall differentiation. The spore wall is multilayered, sometimes with distinct thickening at the sides or septa. In addition to apothecia, ''Buellia'' may also reproduce asexually through structures called

pycnidia A pycnidium (plural pycnidia) is an asexual fruiting body produced by mitosporic fungi, for instance in the order Sphaeropsidales ( Deuteromycota, Coelomycetes) or order Pleosporales (Ascomycota, Dothideomycetes). It is often spherical or inve ...

, which produce simple, (rod-shaped), or (thread-like)

conidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...

(asexual spores). The

conidiophore A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an Asexual reproduction, asexual, non-motility, motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word f ...

s (structures that bear the conidia) within these pycnidia can vary in length and branching.

Selected species

There are almost a thousand species accepted in the genus ''Buellia'', including: *'' Buellia abstracta'' *'' Buellia asterella'' *'' Buellia badia'' *'' Buellia concinna'' *'' Buellia disciformis'' *'' Buellia dispersa'' *'' Buellia spuria''

Gallery

Image:Buellia.disciformis.jpg, '' Buellia disciformis'' Image:Buellia_stillingiana.jpg, '' Buellia stillingiana'' Image:Buellia disciformis-2.jpg, Photograph of a cross section of an apothecium from ''B. disciformis'' taken through a compound microscope (x400), showing numerous brown, 1-septate spores per ascus. Image:Buellia disciformis-4.jpg, Photograph of brown, 1-septate (2-celled) spores from ''B. disciformis'' taken through a compound microscope, x1000. (spores measure 27 x 11 micrometres)

References

{{Authority control * Caliciales genera Lichen genera Taxa described in 1846 Taxa named by Giuseppe De Notaris