''Thamnolia tundrae'' is a species of

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 ...

in the family

Icmadophilaceae The Icmadophilaceae are a family of lichen-forming fungi in the order Pertusariales. The family was circumscribed in 1993 by the mycologist Dagmar Treibel. It contains 9 genera and 35 species. Description Icmadophilaceae species are usually c ...

. Its distribution covers the

arctic tundra In physical geography, a tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: Arctic, Alpine, and Antarctic. Tundra vegetation is ...

of Eurasia and extends to the North American

Aleutian Islands The Aleutian Islands ( ; ; , "land of the Aleuts"; possibly from the Chukchi language, Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before Alaska Purchase, 1867, the Catherine Archipelago—are a chain ...

. Its

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 ...

features white, hollow, cylindrical tufts, which are morphologically the same as the other members of genus '' Thamnolia''. ''Thamnolia tundrae'', however, is

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 from these other similar species. Secondary compounds found in the lichen include baeomycesic acid and squamatic acid. The species is suspected to have survived the latest

glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate be ...

in coastal refugia in regions close to its current range.

Taxonomy

''Thamnolia tundrae'' was described as a new species in 2018 by Ioana Onut-Brännström and

Leif Tibell Leif Tibell (born 16 November 1944) is a Swedish lichenologist and Emeritus Professor at the University of Uppsala. He is known for his expertise on calicioid lichens. He was awarded the Acharius Medal in 2012 for lifetime achievements in lich ...

after multilocus phylogenetic analyses showed that the genus '' Thamnolia'' contains three genetically distinct but outwardly very similar lineages. The new

taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

corresponds to "Lineage A" of earlier studies, a

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 ...

that differs from others in its genus chiefly in

DNA sequence A nucleic acid sequence is a succession of bases within the nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. This succession is denoted by a series of a set of five different letters that indicate the order of the nu ...

s and chemistry. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

was collected on Täljstensvalen mountain (

Jämtland Jämtland () is a historical provinces of Sweden, province () in the centre of Sweden in northern Europe. It borders Härjedalen and Medelpad to the south, Ångermanland to the east, Lapland, Sweden, Lapland to the north and Trøndelag and Norw ...

, Sweden) and is preserved in the UPS herbarium (specimen L-812491). Although morphologically indistinguishable from '' T. subuliformis'' and '' T. vermicularis'', ''T. tundrae'' forms a well-supported

in analyses of up to six nuclear markers and is fixed for a UV-positive chemical profile, supporting its recognition as a separate species. In a 2019 reassessment of the "troublesome genus" ''Thamnolia'',

Per Magnus Jørgensen Per Magnus Jørgensen (born 1944) is a Norwegian botanist and lichenologist, and Professor Emeritus of systematic botany at the University of Bergen. He is known for his work on the lichen families Pannariaceae and Collemataceae. Jørgensen wa ...

proposed that the three lineages delimited by multilocus phylogenies—''T. vermicularis'', ''T. subuliformis'' and ''T. tundrae''—should be treated as subspecies of a broadly circumscribed ''T. vermicularis''. He argued that because the lineages are morphologically indistinguishable yet occupy largely

allopatric Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...

ranges, their differentiation fits the traditional concept of infraspecific geographic races rather than full species status. Accordingly, Jørgensen recognised ''T. vermicularis'' subsp. ''vermicularis'' (widespread), subsp. ''taurica'' (eastern Alps) and subsp. ''tundrae'' (Arctic), and he published the

new combination In Taxonomy (biology), biological taxonomy, a combinatio nova (abbreviated comb. nov. or n. comb.) refers to the formal renaming of an organism's scientific name when it is transferred to a different genus, reclassified within a different specie ...

''Thamnolia vermicularis'' subsp. ''tundrae''. Despite this proposed reduction in rank, the change has not been universally adopted.

Index Fungorum ''Index Fungorum'' is an international project to index all formal names (scientific names) in the fungus kingdom. As of 2015, the project is based at the Royal Botanic Gardens, Kew, one of three partners along with Landcare Research and th ...

still lists ''Thamnolia tundrae'' as the current, accepted species-level name, indicating continued support for its recognition as a distinct species as of July 2025.

Description

The lichen forms chalk-white, hollow cylinders (

podetia A podetium (plural: podetia) is the upright secondary thallus in ''Cladonia'' lichens. It is a hollow stalk extending from the . Podetia can be pointed stalks, club like, cupped, or branched in shape and may or may not contain the ascocarp, the f ...

) that can be unbranched or weakly branched, standing erect or lying prostrate in mats. Each cylinder grows a few millimetres to several centimetres long and is essentially smooth, although tufts may develop where branches arise. Because the species reproduces mainly by fragmenting, no sexual

fruiting bodies The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cyc ...

(

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 ...

) have been observed. The

is a skinny, worm-like tube of fungal tissue densely packed with microscopic

green algae 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 ...

(the ), giving it a tough, stringy feel. Spot tests are diagnostic: a dab of

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 (K) or para-phenylenediamine (PD) turns the yellow, and the thallus

fluoresce Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...

s brilliant white under long-wave ultraviolet light. These reactions reflect the presence of the

secondary metabolite Secondary metabolites, also called ''specialised metabolites'', ''secondary products'', or ''natural products'', are organic compounds produced by any lifeform, e.g. bacteria, archaea, fungi, animals, or plants, which are not directly involved ...

s (

lichen product Lichen products, also known as lichen substances, are organic compounds produced by a lichen. Specifically, they are secondary metabolites. Lichen products are represented in several different chemical classes, including terpenoids, orcinol deri ...

s) baeomycesic and squamatic acids.

Molecular A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, ...

studies show that the photobiont belongs to '' Trebouxia simplex'' (clades 1 and 2). Taken together, colourless cylinders, fixed UV-positive chemistry and a specific algal partner distinguish ''T. tundrae'' when DNA data are considered.

Habitat and distribution

''Thamnolia tundrae'' is restricted to the

Arctic tundra In physical geography, a tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: Arctic, Alpine, and Antarctic. Tundra vegetation is ...

of the Northern Hemisphere. Verified collections are known from northern Sweden and Norway, across the Siberian Arctic of Russia, and eastward to the

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

. It has not been recorded south of the

tree line The tree line is the edge of a habitat at which trees are capable of growing and beyond which they are not. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually low ...

, and within its range it often grows beside (but genetically separate from) the circumpolar ''T. subuliformis'' while remaining

with the alpine-montane ''T. vermicularis''. Field observations indicate a preference for open, wind-swept tundra soils and gravel where snow cover is thin and competition from

vascular plant Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...

s is low.

Population genetic Population genetics is a subfield of genetics that deals with genetic differences within and among populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as adaptation, speciation, and popula ...

evidence suggests the species may have survived the

Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Last Glacial Coldest Period, was the most recent time during the Last Glacial Period where ice sheets were at their greatest extent between 26,000 and 20,000 years ago. Ice sheets covered m ...

in coastal refugia near its present range before expanding onto newly deglaciated ground.

References

{{Taxonbar, from=Q108425880 Pertusariales Lichen species Lichens described in 2018 Lichens of Asia Lichens of Europe Taxa named by Leif Tibell Lichens of the Arctic