''Peltigera rufescens'', the field dog lichen or field pelt, is a species of

terricolous A terricolous lichen is a lichen that grows on the soil as a substrate. An example is some members of the genus ''Peltigera ''Peltigera'' is a genus of approximately 100 species of foliose lichens in the family Peltigeraceae. Commonly known as ...

(ground-dwelling),

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 diverse ...

in the family Peltigeraceae. The common and widespread species has a

cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The ext ...

. The lichen has a surface that is densely covered with a soft, velvety layer, extending from the edges to the centre. The edges of this lichen typically curl upwards, revealing that can be up to 10 millimetres wide. Beneath, it possesses a network of rhizines, which are root-like structures that merge together into a thick mat, anchoring the lichen to its .

Taxonomy

The lichen was first formally described as a variety of ''Lichen caninus'' in 1770 by Friedrich Wilhelm Weiss. At that time, lichens were classified in the eponymous genus ''Lichen'', based on the influence of

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

and his 1753 work ''

Species Plantarum ' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genera. It is the first work to consistently apply binomial names and was the ...

''.

Alexander von Humboldt Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 17696 May 1859) was a German polymath, geographer, naturalist, explorer, and proponent of Romantic philosophy and science. He was the younger brother of the Prussian minister, p ...

transferred the

taxon In biology, a taxon (back-formation from ''taxonomy''; plural 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 nam ...

to the genus ''

Peltigera ''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 (growing on soil), but can also occur on moss, trees, ...

'' and promoted it to the status of species in 1793. Vernacular names used for the species in North America include "field dog lichen" and "field pelt". The complete

mitochondrial genome Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

sequence of ''Peltigera rufescens'' was published in 2021. It has 65,199

base pairs A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...

and a

cytosine Cytosine () ( symbol C or Cyt) is one of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an am ...

guanine Guanine () ( symbol G or Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine (uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside is called ...

content of 26.7%.

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 suggests a close relationship with '' Peltigera membranacea''.

Description

''Peltigera rufescens'' has a grey to brown coloured

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 wer ...

that is often covered with a heavy tomentum (closely matted or fine hairs). It forms rosettes up to in diameter. The lobes comprising the thallus usually measure wide and have edges that are curled upwards. The undersurface of the thallus is strongly veined, dark in colour with a paler margin. Rhizines on the underside affix the lichen to its substrate; near the centre they are so dense so as to form an almost continuous mat. Fruit bodies, or apothecia, are common in this species. They are saddle shaped and dark red brown in colour.

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 o ...

and soredia are absent in this species. The

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 ...

s usually have between 3 and 5

septa The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people in five coun ...

and measure 40–70 by 3–5

μm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

. Conidiomata are sometimes produced by the lichen; the

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

are 7–10 by 2.5–4.5 μm. The

photobiont A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

from the genus ''

Nostoc ''Nostoc'', also known as star jelly, troll’s butter, spit of moon, fallen star, witch's butter (not to be confused with the fungi commonly known as witches' butter), and witch’s jelly, is the most common genus of cyanobacteria found in vari ...

''. No lichen products are associated with ''Peltigera rufescens'', and consequently, the expected results of standard

lichen spot tests A spot test in lichenology is a spot analysis used to help identify lichens. It is performed by placing a drop of a chemical on different parts of the lichen and noting the colour change (or lack thereof) associated with application of the chemical ...

are all negative. If grown in a metal-polluted environment, ''Peltigera rufescens'' will have a reduction in thallus size and in rhizine length, as well as denser growth of the rhizines, veins that are more profusely branched, and an increase in volume of the medulla. When treated with

mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...

, or

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...

, ''P. rufescens'' chlorophyll α and

carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, and Fungus, fungi. Carotenoids give the characteristic color to pumpki ...

concentrations will also decrease. As with other lichens, ''P. rufescens'' is a bioaccumulator of

heavy metals upright=1.2, Crystals of osmium, a heavy metal nearly twice as dense as lead">lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals are generally defined as ...

. This may be due to the thallus having a large surface area in contact with the substrate. ''P. rufescens'' also has free

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

concentrations higher than other lichens in similar polluted habitats, comparable to

vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...

s, suggesting that this may play a role in heavy metal tolerance.

Reproductive structures

In 1971, Marie-Agnès Letrouit-Galinou and R. Lallemant published a study on the thallus, apothecia, and asci of ''Peltigera rufescens'', using histological techniques and microscopic examination. The thallus was described as having a "cladomian" structure, evolving from axial filaments that are lodged in the veins. These filaments give rise to both short ventral pleuridia (lateral branchlets) and well-developed dorsal ramifications. The formation of apothecia is initiated by a limited number of marginal dorsal pleuridia, leading to a primary thallus resembling those in the families

Lecanoraceae The Lecanoraceae are a family of lichenized fungi in the order Lecanorales. Species of this family have a widespread distribution. Taxonomy Lecanoraceae was circumscribed by German lichenologist Gustav Wilhelm Körber in 1855. Genera According ...

and

Graphidaceae The Graphidaceae are a family of lichens in the order Ostropales. Distribution and ecology The vast majority of Graphidaceae species are restricted to the tropics. Most Graphidaceae species are epiphytic (i.e. they grow only on plants). Gener ...

, with a distinct development process marked by a lengthy angiocarpic stage (a phase in the development where the apothecium is initially formed as a closed structure, enclosing the asci and ascospores). The asci were identified as and 'archaeasce', signifying a complex reproductive structure. Additionally, the research investigated the cladomian, multi-axial structure of the thallus in detail, comparing it to similar structures in algae and highlighting the differentiation between dorsal and ventral pleuridia, which contribute to the thallus's growth and structure. Peltigera T81

Habitat and distribution

''Peltigera rufescens'' is a common and widespread lichen with a

. It is most often encountered in dry, sunny habitats. It prefers more or less basic soils. It also grows on

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

and

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

(rarely on

silicate In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is al ...

rocks) as well as nutrient-rich silicate soils, including diverse environments like calcareous

grassland A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...

s and stone structures. Individuals that grow in association with mosses tend to grow more robustly and have a higher amount of chlorophyll α then those that do not. Not only does the moss provides a buffer against extremes in temperature variation, the moss-associated thalli have higher

photosynthetic Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...

rates, and increased protection against desiccation. Additionally, their thalli are thicker, leading to enhanced water retention. Mosses that have been recorded associating with ''Peltigera rufescens'' include '' Racomitrium heterostichum'', ''

Campylopus introflexus ''Campylopus introflexus'', also known as the heath star moss, is a species of moss. The first description of the species was made by Johannes Hedwig as ''Dicranum introflexum'' in 1801. Description Individual plants measure , with lanceolate l ...

'', ''

Hypnum cupressiforme ''Hypnum cupressiforme'', the cypress-leaved plaitmoss or hypnum moss, is a common and widespread species of moss belonging to the genus ''Hypnum''. It is found in all continents except Antarctica and occurs in a wide variety of habitats and clim ...

'', and ''

Polytrichum juniperinum ''Polytrichum juniperinum'', commonly known as juniper haircap or juniper polytrichum moss, is an evergreen and perennial species of moss that is widely distributed, growing on every continent including Antarctica. A study of the high-elevation

biological soil crust Biological soil crusts are communities of living organisms on the soil surface in arid and semi-arid ecosystems. They are found throughout the world with varying species composition and cover depending on topography, soil characteristics, climate, ...

associated with the volcanic

tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they rem ...

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

's Haleakalā Crater found that ''Peltigera rufescens'' was one of the two important components of this crust (the other was the moss ''

Grimmia torquata ''Grimmia'' is a genus of mosses (Bryophyta), originally named by Jakob Friedrich Ehrhart in honour of Johann Friedrich Carl Grimm, a physician and botanist from Gotha, Germany. Geographic distribution Although predominantly occurring in th ...

'') and occurred in about a quarter of soil specimens sampled.

Ecology

'' Preussia peltigerae'', '' Dinemasporium strigosum'', '' Lichenopenicillus versicolor'', '' Nectriopsis lecanodes'', '' Norrlinia peltigericola'', and ''

Scutula didymospora ''Scutula'' is a genus of lichenicolous fungi in the family Ramalinaceae. Taxonomy The genus ''Scutula'' was circumscribed by French botanist Louis René Étienne Tulasne in 1862. The limits of the generic circumscription as well as the limits ...

'' are

lichenicolous fungi A lichenicolous fungus is a parasitic fungus that only lives on lichen as the host. A lichenicolous fungus is not the same as the fungus that is the component of the lichen, which is known as a lichenized fungus. They are most commonly specific to ...

that use ''Peltigera rufescens'' as a

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

. In the case of ''Scutula didymospora'', the relationship appears to be commensalistic, as the fungus, which develops on the underside of the thallus, does not cause any damage, discolouration or

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...

s. In one experiment, to test the effect of thallus hydration on

metabolic activity Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...

, the

photosystem II Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants, algae, and cyanobacteria. Within the photosystem ...

fluorescence of ''Peltigera rufescens'' was monitored for a full year. The lichen was inactive for 46.5% of the time, active during daylight for 25.6%, and hydrated at night for 27.9% of the time. Its photosynthetic activity and moisture levels were correlated with environmental conditions, with four distinct activity patterns discerned. Despite previous experimental findings suggesting high light could be harmful when the lichen is hydrated, field observations found little evidence of damage, suggesting an unknown photoprotection mechanism possibly involving certain

s. In a study examining the effects of long-term

UV-B Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...

radiation on lichen species, ''Peltigera rufescens'', typically found in open

meadow A meadow ( ) is an open habitat, or field, vegetated by grasses, herbs, and other non-woody plants. Trees or shrubs may sparsely populate meadows, as long as these areas maintain an open character. Meadows may be naturally occurring or artifi ...

spaces, demonstrated increased

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

content and

superoxide dismutase Superoxide dismutase (SOD, ) is an enzyme that alternately catalyzes the dismutation (or partitioning) of the superoxide () radical into ordinary molecular oxygen (O2) and hydrogen peroxide (). Superoxide is produced as a by-product of oxygen me ...

activity, indicating a possible adaptive response to oxidative stress caused by UV-B exposure. This lichen species displayed a higher resilience to UV-B compared to '' Peltigera aphthosa'', suggesting a species-specific response to UV-B radiation that likely stems from their typical habitat's light conditions.

Bioactivity

Laboratory experiments suggest that

extract An extract is a substance made by extracting a part of a raw material, often by using a solvent such as ethanol, oil or water. Extracts may be sold as tinctures, absolutes or in powder form. The aromatic principles of many spices, nuts, h ...

s of ''Peltigera rufescens'' have insecticidal activity against the maize weevil (''Sitophilus zeamais'').

References

{{Taxonbar, from=Q10549593 rufescens Lichen species Lichens described in 1793 Lichens of Europe Lichens of North America Cosmopolitan lichens