''Usnea trichodea'', commonly known as bony beard lichen, is a pale straw-colored

fruticose 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 mor ...

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.pendant A pendant is a loose-hanging piece of jewellery, generally attached by a small loop to a necklace, which may be known as a "pendant necklace". A pendant earring is an earring with a piece hanging down. Its name stems from the Latin word ...

growth form. It grows on trees and is native to eastern North America.

Description

''Usnea trichodea'' hangs from the branches and twigs of trees and can reach a length of . The main branches are smooth and slender, with a diameter of less than ; they send out side branches at an obtuse angle at intervals. The

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 ...

is divided into articulating sections with raised cracks between; the medulla is dense and white while the axis is reddish-brown. It could be confused with '' Usnea longissima'' but the branching structure and reddish axis are distinctive.

Distribution and habitat

''Usnea trichodea'' occurs in eastern North America where it grows on trees. Its range extends from

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

New Brunswick New Brunswick (french: Nouveau-Brunswick, , locally ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. It is the only province with both English and ...

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...

Prince Edward Island Prince Edward Island (PEI; ) is one of the thirteen Provinces and territories of Canada, provinces and territories of Canada. It is the smallest province in terms of land area and population, but the most densely populated. The island has seve ...

, and eastern

Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...

in Canada, southwards to

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

and

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

in the United States.

Ecology

Some lichens are extremely sensitive to pollution, and it has been found that ''Usnea trichodea'' and ''

Evernia ''Evernia'' is a genus of bushy lichens in the family Parmeliaceae. Description Oakmoss '' Evernia prunastri'' is used as a fixative agent in Eau de Cologne within the perfume industry. It is green on top and white on bottom, and divides eve ...

'' spp. will sicken and die if exposed to

sulphur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...

. These lichens can be used as indicators of air pollution. Researchers found that in Nova Scotia, the

tricolored bat The tricolored bat (''Perimyotis subflavus'') is a species of microbat native to eastern North America. Formerly known as the eastern pipistrelle, based on the incorrect belief that it was closely related to European '' Pipistrellus'' species, t ...

(''Perimyotis subflavus''), which roosts in tree foliage over much of its range, was roosting exclusively in the dangling

thalli 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 were ...

of ''Usnea trichodea''; the lichen was typically growing on

conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extan ...

, the majority of which were species of

spruce A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. ''Picea'' is the sole genus in the subfami ...

. The authors of the study speculated that the tricolored bats might use the lichen, which contains

usnic acid Usnic acid is a naturally occurring dibenzofuran derivative found in several lichen species with the formula C18H16O7. It was first isolated by German scientist W. Knop in 1844 and first synthesized between 1933-1937 by Curd and Robertson. Usnic a ...

, to reduce parasitism, as the bats were found to be free of

ectoparasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

References

{{Taxonbar, from=Q21303511 trichodea Lichen species Lichens of North America Lichens described in 1803 Taxa named by Erik Acharius