''Violella'' 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 two species of

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 ...

s in the family

Tephromelataceae The Tephromelataceae are a family of lichenized fungi in the order Lecanorales. The family was circumscribed by Austrian lichenologist Josef Hafellner in 1984. Tephromelataceae comprises the genera '' Tephromela'', '' Calvitimela'', '' Mycoblast ...

. The genus is characterized by its brownish inner

ascospore In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse Division (botany), division of fungi. After two parental cell nucleus, nuclei fuse, the ascu ...

walls, brilliant violet hymenial pigment (called Fucatus-violet), and

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 ...

chemistry. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, '' Violella fucata'', was originally placed in genus '' Mycoblastus'', but

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

analysis showed that this species as well as the Asian species '' V. wangii'' formed a

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

ally distinct

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

and warranted placement in a new genus. The generic name ''Violella'', a

diminutive A diminutive is a word obtained by modifying a root word to convey a slighter degree of its root meaning, either to convey the smallness of the object or quality named, or to convey a sense of intimacy or endearment, and sometimes to belittle s ...

form of the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''viola'', refers to the characteristic

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 ...

colour.

Taxonomy

The genus ''Violella'' was erected in 2011 by

Toby Spribille Toby Spribille is a lichenologist, specialising in evolution and taxonomy. He identified the presence of yeast cells as an additional fungal component of some lichens. He works at University of Alberta and is the Canada Research Chair in Symbiosi ...

and colleagues after DNA analyses showed that the Northern-Hemisphere lichen ''Mycoblastus fucatus'' and an undescribed Asian relative formed a well-supported

within the family

, separate from both ''Mycoblastus'' ''

sensu ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...

stricto'' (in the strict sense) and the genera ''Tephromela'' and ''Calvitimela''. Spribille's team judged that rolling these species into an already large ''Tephromela'' would blur useful generic boundaries, so they created ''Violella'' to accommodate the pair. The name is a

of ''Viola'' and alludes to the striking violet granules that suffuse the

of all known species. ''Violella fucata''—first described by

James Stirton James Stirton (1833 – 14 January 1917) was a Scottish physician and one of Scotland's leading experts on cryptogamic botany. His investigations in bryology and lichenology earned him a world-wide reputation. Biography Stirton was born in Coupar ...

in 1879 as ''Lecidea fucata''—was selected as the

; over the years it has also travelled through the genera ''Megalospora'' and ''Mycoblastus'' before molecular data clarified its affinities. The second member, ''V. wangii'', was described alongside the genus to encompass East-Asian material that shares the same violet pigment but differs in thallus size, chemistry and spore dimensions. Together the species are distinguished from superficially similar taxa by four linked traits: (i) the "Fucatus-violet" pigment, which turns peacock-green in K and raspberry-red in N; (ii) ''

Biatora ''Biatora'' is a genus of lichens in the family Ramalinaceae. Originally circumscribed in 1817,Fries EM, Sandberg A. (1817). ''Lichenum dianome nova''. Lund. the genus consists of crustose and squamulose lichens with green algal photobionts, bi ...

''-type asci rather than ''

Lecanora ''Lecanora'' is a genus of lichen commonly called rim lichens.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, Lichens in the genus '' Squamarina'' are also called rim lichens. Members of the genus have roughly c ...

''-type; (iii) large, simple

s whose inner walls become brown with age; and (iv) an atranorin-based chemistry instead of the alectoronic or fumarprotocetraric acids typical of allied genera.

Phylogenetically In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

, ''Violella'' nests deep within Tephromelataceae but remains

sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...

to both ''Tephromela'' and ''Calvitimela'', supporting its recognition as a discrete lineage rather than a subclade of either genus. Ongoing sampling across

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

and

montane Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures lapse rate, fall as elevation increases, causing the ecosystem to stratify. This stratification is ...

forests suggests the genus has a circumboreal–East-Asian distribution, and further fieldwork may yet reveal additional species that share its unique combination of violet pigments, ''Biatora''-type asci and melanising spore walls.

Description

''Violella'' forms thin, crust-like patches that sit tightly on bark or wood. The surface is broken into tiny angular flakes or low warts and is usually white to ash-grey, sometimes clothed in a fine powder of

soredia Soredia are common reproduction, reproductive structures of lichens. Lichens asexual reproduction, reproduce asexually by employing simple fragmentation and production of soredia and isidia. Soredia are powdery propagules composed of fungus, fung ...

(minute granules that contain both partners of the lichen and serve as

propagule In biology, a propagule is any material that functions in propagating an organism to the next stage in its life cycle, such as by dispersal. The propagule is usually distinct in form from the parent organism. Propagules are produced by organisms ...

s). A layer of microscopic

green alga The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( ...

e ( photobiont) is embedded in a white fungal

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 ...

beneath a protective . No distinct prothallus is developed. Chemical tests show

atranorin Atranorin is a chemical substance produced by some species of lichen. It is a secondary metabolite belonging to a group of compounds known as depsides. Atranorin has analgesic, anti-inflammatory, antibacterial, antifungal, cytotoxic, antioxidant, ...

together with a

depsidone Depsidones (+ " depside" + "one") are chemical compounds that are sometimes found as secondary metabolites in lichens. They are esters that are both depsides and cyclic ethers. An example is norstictic acid Norstictic acid is a depsidone produ ...

and a

fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...

in the

. The reproductive bodies are distinctive: black, disc-shaped

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 ...

that begin immersed in the crust and later sit flush or slightly raised on a thin ring-like "thalline cushion" of tightly intertwined

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

e; this cushion is evident around very young discs but soon becomes overgrown and excluded. Under the microscope the spore layer (

) is shot through with vivid violet granules—"Fucatus-violet"—which flash peacock-green in

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...

solution and raspberry-red in

sodium hypochlorite Sodium hypochlorite is an alkaline inorganic chemical compound with the formula (also written as NaClO). It is commonly known in a dilute aqueous solution as bleach or chlorine bleach. It is the sodium salt of hypochlorous acid, consisting of ...

. There is no separate ; the violet pigment is dispersed through the hymenium. The inner cup wall () is highly reduced and composed of hyphae indistinguishable from 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 ...

, and the paraphyses are comparatively broad, straight to slightly curved, connected by delicate cross-bridges that separate easily in water. Each

ascus An ascus (; : asci) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some gen ...

is of the ''Biatora'' type and almost always contains two large, simple

s; as they mature, a second, internal wall develops and turns brown, a feature unique within the Tephromelataceae. Tiny flask-shaped

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 ...

are rare; when present they release straight, colourless

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 ...

References

{{Taxonbar, from=Q21229693 Lecanorales genera Lecanorales Lichen genera Taxa described in 2011 Taxa named by Toby Spribille