{{Short description|Species of lichen}} {{Speciesbox | name = Bony beard lichen | image = Usnea trichodea - Flickr - pellaea.jpg | image_caption = | status = G5 | status_system = TNC | status_ref = <ref name=NS>{{cite NatureServe |id=2.122698 |title=''Usnea trichodea'' |access-date=12 November 2025}}</ref> | taxon = Usnea trichodea | authority = Ach. (1803) | synonyms_ref = | synonyms = }}
'''''Usnea trichodea''''', commonly known as '''bony beard lichen''',<ref name=NatureServe>{{cite web |url=http://explorer.natureserve.org/servlet/NatureServe?searchName=Usnea+trichodea |title=''Usnea trichodea'' - Ach. |publisher=NatureServe |access-date=29 October 2019}}</ref> is a pale straw-colored fruticose lichen with a pendant 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 {{convert|30|cm|in|0|abbr=on}}. The main branches are smooth and slender, with a diameter of less than {{convert|0.4|mm|in|2|abbr=on}}; they send out side-branches at an obtuse angle at intervals. The thallus 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.<ref name=Brodo>{{cite book|author1=Brodo, Irwin M.|author2=Sharnoff, Sylvia Duran|author3=Sharnoff, Stephen |title=Lichens of North America |url=https://books.google.com/books?id=YyS-hS15Ty4C&pg=PA726 |year=2001 |publisher=Yale University Press|isbn=978-0-300-08249-4 |page=726}}</ref>
==Distribution and habitat== ''Usnea trichodea'' occurs in eastern North America where it grows on trees. Its range extends from Ontario, New Brunswick, Newfoundland, Nova Scotia, Prince Edward Island, and eastern Quebec in Canada, southwards to Texas and Florida in the United States.<ref name=NatureServe/>
==Ecology== Some lichens are extremely sensitive to pollution, and it has been found that ''Usnea trichodea'' and ''Evernia'' spp. will sicken and die if exposed to sulphur dioxide. These lichens can be used as indicators of air pollution.<ref name=Miller>{{cite book|author=Miller, G. Tyler |title=Living in the Environment: Principles, Connections, and Solutions|url=https://books.google.com/books?id=dbgFAAAAQBAJ&pg=PA439 |year=2006 |publisher=Cengage Learning|isbn=1-111-79687-4 |page=439}}</ref>
Researchers found that in Nova Scotia, the tricolored bat (''Perimyotis subflavus''), which roosts in tree foliage over much of its range, was roosting exclusively in the dangling thalli of ''Usnea trichodea''; the lichen was typically growing on conifers, the majority of which were species of spruce.<ref name=Poissant/> The authors of the study speculated that the tricolored bats might use the lichen, which contains usnic acid, to reduce parasitism, as the bats were found to be free of ectoparasites.<ref name=Poissant>{{cite journal|doi=10.2980/17-4-3352|title=Use of lichen as a roosting substrate by ''Perimyotis'' subflavus, the tricolored bat, in Nova Scotia |journal=Écoscience |volume=17 |issue=4 |pages=372–378 |year=2010 |last1=Poissant |first1=Joseph A. |last2=Broders |first2=Hugh G. |last3=Quinn |first3=Greg M.|bibcode=2010Ecosc..17..372P |s2cid=86543052 }}</ref>
==References== {{Reflist}}
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trichodea Category:Lichen species Category:Lichens of North America Category:Lichens described in 1803 Category:Taxa named by Erik Acharius