Lichens of the Sierra Nevada have been little studied. A lichen is a composite organism consisting of a

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

(the mycobiont) and a photosynthetic partner (the photobiont or phycobiont) growing together in a symbiotic relationship. One classification of Sierra Nevada lichens is according to functional groups, by the

National Park Service The National Park Service (NPS) is an agency of the United States federal government within the U.S. Department of the Interior that manages all national parks, most national monuments, and other natural, historical, and recreational propert ...

. These functional groups overlap with each other. These include

forage Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used ...

lichens (eaten by animals), nitrogen fixers (can take

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

molecules from the air and attach them to other molecules),

acidophiles Acidophiles or acidophilic organisms are those that thrive under highly acidic conditions (usually at pH 5.0 or below). These organisms can be found in different branches of the tree of life, including Archaea, Bacteria,Becker, A.Types of Bacte ...

(acid loving lichens), wolf lichens,

crustose Crustose is a 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 substrates at all points. ''Crustose'' is found on rocks ...

lichens on rock, crustose lichens on bark and wood, biotic soil crusts, aquatic lichens, other green

algal Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mi ...

macrolichens, and pin lichens ( calicoids)”. These functional groups overlap. In this article, we include wolf lichens as a subsection of crustose lichens growing on wood.

Forage lichens

Forage lichens includes hanging, hairlike species that serve as food for animals and humans, including by Native Americans. Wila (''

Bryoria fremontii ''Bryoria fremontii'' is a dark brown, horsehair lichen that grows hanging from trees in western North America, and northern Europe and Asia. It grows abundantly in some areas, and is an important traditional food for a few First Nations in No ...

'') is the most important species in this group. It is notable for its palatability because it lacks defensive chemicals commonly found in other lichens that protect them against being eaten (

herbivory A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

). It becomes more increasingly more rare moving south in the Sierras. It is one of the only food sources in the harsh winters of the Sierras, including for the northern flying squirrel ('' Glaucomys sabrinus'') and Douglas squirrel ('' Tamiasciurus douglasii''). Mule deer (''

Odocoileus hemionus The mule deer (''Odocoileus hemionus'') is a deer indigenous to western North America; it is named for its ears, which are large like those of the mule. Two subspecies of mule deer are grouped into the black-tailed deer. Unlike the related w ...

'') may also depend on it.

Nitrogen fixers

Lichens with cyanobacteria as a symbiotic partner (

cyanolichen Cyanolichens are lichens that apart from the basic fungal component ("mycobiont"), contain cyanobacteria, otherwise known as blue-green algae, as the photosynthesizing component ("photobiont"). Overall, about a third of lichen photobionts are cyan ...

s) convert atmospheric

into forms usable by plants and animals (

nitrogen fixation Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...

). They are common in the relatively warm and dry Sierras, though less common than in cool oceanic climates. They are typically found on mossy boulders, rotting logs, trunks of hardwoods, and bases of trees in general. Common genera include ''

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, ...

'', '' Fuscopannaria'', ''

Collema ''Collema'' (jelly lichen) is a genus of lichens in the family Collemataceae. The photobiont is the cyanobacterium genus ''Nostoc''.Dobson, F.S. (2000) Lichens, an illustrated guide to the British and Irish species. 4th edition. Richmond publish ...

'', and '' Leptogium''.

Crustose lichens

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

s grow flat against the surface that the colonies are growing on ( substrate), typically rocks or wood. The plant grows tightly appressed to the substrate, and is very close to the substrates at all points, forming a biological layer. There is overlap between crustose lichens growing on rock with those growing on wood, as well as with lichens listed in other sections of this article. Among the most brightly colored Sierra Nevada crustose lichens are the bright yellow '' Pleopsidium flavum'' and '' Pleopsidium chlorophanum'', and the orange '' Caloplaca trachyphylla''.Crustose Rock Lichens, Wayne P. Armstrong, Waynes World online textbook

/ref>

On rock

Crustose lichen communities are part of the aesthetic appeal to visitors of

Yosemite National Park Yosemite National Park ( ) is an American national park in California, surrounded on the southeast by Sierra National Forest and on the northwest by Stanislaus National Forest. The park is managed by the National Park Service and covers an ...

and

Sequoia National Park Sequoia National Park is an American national park in the southern Sierra Nevada east of Visalia, California. The park was established on September 25, 1890, and today protects of forested mountainous terrain. Encompassing a vertical relief ...

. They form dark vertical drip-like stripings along drainage tracks in the rock faces, resulting in Native Americans giving the name "Face of a Young Woman Stained with Tears" to

Half Dome Half Dome is a granite dome at the eastern end of Yosemite Valley in Yosemite National Park, California. It is a well-known rock formation in the park, named for its distinct shape. One side is a sheer face while the other three sides are smoo ...

. Their tight adherence to the rocks give them the appearance of being "painted" on, and up close they appear as intricate multicolored patchwork mosaics. They often completely cover the exposed surface of the rock. They add to rock weathering. These crustose rock lichens lack rhizenes and a lower

cortex (lichen) In botany, a cortex is an outer layer of a stem or root in a vascular plant, lying below the epidermis but outside of the vascular bundles. The cortex is composed mostly of large thin-walled parenchyma cells of the ground tissue system and shows ...

. The dark vertical stains along the drainage tracks are either mosses, or of four color types of lichen, each with a slightly different color. Appearing black from a distance, but brown up close, is the abundant ''

Lecidea atrobrunnea ''Lecidea atrobrunnea'' is a crustose lichen in the Lecideaceae family, found in mountains of the continental western United States and Alaska. With other lichen communities, it forms dark vertical drip-like stripings along drainage tracks in th ...

''. Also abundant in these black-from-a-distance stripes are '' Dimelaena thysanota'' and dark gray ''

Rhizocarpon ''Rhizocarpon'' is a genus of crustose, saxicolous (or sometimes lichenicolous), lichens in the family Rhizocarpaceae. The genus is common in arctic-alpine environments, but also occurs throughout temperate, subtropical, and even tropical regio ...

'' species. More gray appearing vertical stripes have '' Aspecilia'' species and '' Koerberia sonomensis'' as major components. '' Staurothele areolata'' and other species of '' Staurothele'' and '' Verrucaria'' appear dark brown closer up. The blackest of the black are likely ''

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 var ...

'' species, containing cyanobacteria. Mixed in are green to dark green stripes that contain mosses. Nitrophilic (nitrogen loving) yellow '' Candelariella'' species can be found on rocks where birds perch and drop their high nitrogen containing waste products, as well as in drainage cracks with higher than normal nitrogen loads.

Fruticose lichens

Wolf lichens

Wolf lichens in the genus '' Letharia'' are the most conspicuous in the Sierra parks because of their brilliant fluorescent yellow or chartreuse coloration. They are typified by ''

Letharia vulpina ''Letharia vulpina'', commonly known as the wolf lichen (although the species name ''vulpina'', from ''vulpine'' relates to the fox), is a fruticose lichenized species of fungus in the family Parmeliaceae. It is bright yellow-green, shrubby and ...

'' (vulpina derives from "fox", not wolf). They are mostly absent at lower elevations, and can then be found on conifer trunks and branches, sometimes completely covering them. ''Letharia'' is the only abundant

fruticose lichen A fruticose lichen is a form of lichen fungi that is characterized by a coral-like shrubby or bushy growth structure. It is formed from a symbiotic relationship of a photobiont such as green algae or less commonly cyanobacteria and one, two or m ...

in the Sierran parks, and composes the bulk of the biomass in '' Sequoia'' groves, and many other types of groves. Estimates have ''Letharia'' species as contributing from 50% to 95% of the total macrolichen biomass in some stands. It contains toxins (e.g.,

vulpinic acid Vulpinic acid is a natural product first found in and important in the symbiosis underlying the biology of lichens. It is a simple methyl ester derivative of its parent compound, pulvinic acid, and a close relative of pulvinone, both of which ...

) to many herbivores and microbes, although there are mixed reports on actual consumption. It is the vulpinic acid that gives it the brilliant yellow color.

Pin lichens (calicoid lichens)

Pin lichens, or calicoid lichens, are lichens with a

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 tiny fruiting bodies with stalks that resemble the head of a pin, whereby the name "pin lichen".

Ecological interactions

About 20 Sierra Nevada bird species are known to use lichens in nests construction.

References

{{Flora of the United States by political division, state=collapsed Ecology of the Sierra Nevada (United States) Sierranevada California nature-related lists Lists of biota of the United States