''Imshaugia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of seven species of

foliose lichen Foliose lichen is one of the morphological classes of lichens, which are complex organisms that arise from the symbiotic relationship between fungi and a photosynthetic partner, typically algae. This partnership allows lichen to live in dive ...

s in the family

Parmeliaceae The Parmeliaceae is a large and diverse family of Lecanoromycetes. With over 2700 species in 71 genera, it is the largest family of lichen-forming fungi. The most speciose genera in the family are the well-known groups: '' Xanthoparmelia'' ( ...

. They are commonly known as starburst lichens.

Taxonomy

The genus was circumscribed by Susan Meyer in 1985 as a segregate of '' Parmeliopsis''. The genus name of ''Imshaugia'' is in honour of Henry Andrew Imshaug (1925–2010), who was an American lichenologist. In a previous study of ''Parmeliopsis'', Meyer noted a group of species (represented by ''P. aleurites'' and ''P. placorodia'') that would be better accommodated in a separate genus. This had been previously noted by other lichenologists: in 1932, Vilmos Gyelnik proposed the

section Section, Sectioning or Sectioned may refer to: Arts, entertainment and media * Section (music), a complete, but not independent, musical idea * Section (typography), a subdivision, especially of a chapter, in books and documents ** Section sig ...

''Pallidifera'' to include the grey species of ''Parmeliopsis''; in 1936 Johannes Hillmann proposed section ''Rectoconidia'' to contain species with short and straight conidia. Meyer created ''Imshaugia'' on the basis of its emergent and partly marginal

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 inverse ...

(they are immersed and laminal in ''Parmeliopsis''), its short, ampulliform (flask-shaped) or bifusiform (tapering at both ends) conidia (these are long and curved in ''Parmeliopsis''), and the presence of '' Cetraria''-type lichenan in its cell walls rather than isolichenan as in ''Parmeliopsis''. The generic name honours Henry Andrew Imshaug, "in recognition of his contributions to lichenology." ''Imshaugia'' species are commonly known as "starburst lichens".

Description

''Imshaugia'' lichens are

foliose Foliose lichen is one of the morphological classes of lichens, which are complex organisms that arise from the symbiotic relationship between fungi and a photosynthetic partner, typically algae. This partnership allows lichen to live in diverse ...

with a mineral-grey to whitish-grey

thallus Thallus (plural: 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. Many of these organisms ...

and a whitish to light brown lower surface. They grow as small rosettes, comprising small lobes measuring 1–2 mm wide. Pseudocyphellae and

soredia Soredia are common reproductive structures of lichens. Lichens reproduce asexually by employing simple fragmentation and production of soredia and isidia. Soredia are powdery propagules composed of fungal hyphae wrapped around cyanobacteria or ...

are absent from the thallus, but

isidia An isidium is a vegetative reproductive structure present in some lichens. Isidia are outgrowths of the thallus surface, and are corticated (i.e., containing the outermost layer of the thallus), usually with a columnar structure, and consisting ...

may be present. The upper

cortex Cortex or cortical may refer to: Biology * Cortex (anatomy), the outermost layer of an organ ** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain'' *** Motor cortex, the regions of the cerebral cortex i ...

is paraplectenchymatous (a cell arrangement where the hyphae are oriented in all directions), measuring 10–20 μm thick, and covered by an epicortex with pores. The

apothecia An ascocarp, or ascoma (), 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. Ascocarps are mos ...

are ''Lecanora''-type, resembling large, concave brown discs.

Ascospore An ascus (; ) 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 genera or ...

s are colourless, ellipsoid, and number eight per ascus. Conidia have a short bacilliform shape with a swelling towards one end, and measure 3–4.5 μm long. The phycobiont in ''Imshaugia'' is

green alga The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...

e – ''

Trebouxia ''Trebouxia'' is a unicellular green alga.Silverside, A. J. (2009). Retrieved from http://www.bioref.lastdragon.org/Chlorophyta/''Trebouxia''.html It is a photosynthetic organism that can exist in almost all habitats found in polar, tropical, a ...

'' in ''I. aleurites'', and '' Myrmecia'' in ''I. placorodia''. The thallus contains thamnolic acid and

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, ...

Habitat and distribution

''Imshaugia'' grows most commonly on the bark and wood of conifers, and prefers woodland habitats that are open and well-lit. They have also been recorded on hardwoods and wood fences. The South American species ''I. sipmanii'', however, is

saxicolous A saxicolous lichen is a lichen that grows on rock. The prefix "sax" from the Latin means "rock" or "stone". Characteristics Saxicolous lichens exhibit very slow growth rates. They may develop on rock substrates for long periods of time, give ...

. ''Imshaugia placorodia'' has been noted to display a preference for the bark of the tree species pitch pine (''Pinus rigida'') and

Jack pine Jack pine (''Pinus banksiana'') is an eastern North American pine. Its native range in Canada is east of the Rocky Mountains from the Mackenzie River in the Northwest Territories to Cape Breton Island in Nova Scotia, and the north-central and ...

(''Pinus banksiana''). The

type species In 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 species that contains the biological type specime ...

, ''Imshaugia aleurites'', is widely distributed in northern North America, having been recorded from the

tree line The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures, extreme snow ...

in the Arctic south through all of the boreal region and most of the

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

region.

Species

*'' Imshaugia aleurites'' *'' Imshaugia angustior'' *'' Imshaugia evernica'' –

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

*'' Imshaugia placorodia'' *'' Imshaugia pyxiniformis'' – Brazil *'' Imshaugia sipmanii'' – Venezuela *'' Imshaugia venezolana'' – Venezuela The species ''Imshaugia subarida'', proposed by John Elix in 2004 (a

new combination ''Combinatio nova'', abbreviated ''comb. nov.'' (sometimes ''n. comb.''), is Latin for "new combination". It is used in taxonomic biology literature when a new name is introduced based on a pre-existing name. The term should not to be confused wi ...

from genus '' Canoparmelia''), has since been transferred to '' Austroparmelina''.

References

{{Taxonbar, from=Q6008411 Parmeliaceae Lichen genera Lecanorales genera Taxa described in 1985