Public Description of Usnea Dill. ex Adans.

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Name: Usnea Dill. ex Adans.
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Description status: Unreviewed
 (Latest review: 2012-03-19 14:45:49 CST (-0500) by jason)

Taxonomic Classification:

Kingdom: Fungi
Phylum: Ascomycota
Class: Lecanoromycetes
Order: Lecanorales
Family: Parmeliaceae


General Description:

Fruticose “hair” lichens with a characteristic rubbery central axis. (Check for the axis but pulling a branch apart and looking for a rubber band-like strand in the center.) Typically greenish-gray to yellowish green, but sometimes reddish or brownish or straw-colored. Some arctic-alpine species are even mostly black. Most grow on trees, especially in maritime regions where there is abundant humidity. Known as “tree beards” or “old man’s beard”, but not to be confused with several other genera of hair lichens or the air plant Tillandsia usneoides.


Diagnostic Description:

Fruticose lichens with usnic acid in the cortex and long mostly terete branches with both a medulla and a tough rubbery central axis. No other genus of lichens possesses this central axis.


U. ceratina
rubbery central strand


Distribution:

Cosmopolitan. Hot spots of diversity in North America are New England and the Maritime Provinces (~27 species present in New Brunswick), Pacific Northwest coast (~24 species along the Oregon coast), Great Lakes and Appalachian Mountains (~20 species in the Great Smoky Mountains), and Sierra Madre Occidental (~16 species).


Habitat:

Most common in canopy and on trunks of both hardwoods and conifers wherever you find frequent mist or fog. Prefers well-lit open forests, especially forest margins such as at the edge of ponds or bluffs.


Look Alikes:

Tillandsia usneoides is a vascular plant related to airplants.

Protousnea, Ramalina thrausta and Alectoria spp. are similar in shape and color, however these two genera have a uniform medulla lacking the rubbery central strand.

Bryoria s. lato. typically have much finer branches and are dark brown to almost black.

Ramalina spp. are similar in color, but generally have conspicuously flattened branches lacking the rubbery central strand.


Usnea scabrata, Alectoria sarmentosa, Ramalina thrausta


Protousnea from Chile


References:

Articus, K., M. Wedin, J.-E. Mattsson, L. Tibell and M. Grube. 2000. Phylogenetic studies in Usnea, in The Fourth IAL Symposium, Progress and Problems in Lichenology at the Turn of the Millennium. Universitat de Barcelona, Barcelona, pp. 100.

Clerc, P. 1987. On the morphology of soralia in the genus Usnea, pp. 99-102 in Preveling, E. (ed.) Progress and Problemsin Lichenology in the Eighties. Bibliotheca Lichenologica 25.

Clerc, P. 1997. Notes on the genus Usnea Dill. ex Adanson. Lichenologist 29: 209-215.

Clerc, P. 1998. Species concepts in the genus Usnea (lichenized Ascomycetes). Lichenologist 30: 321-340.

Clerc, P. 2004. Notes to the genus Usnea Adanson. II, pp. 79-90 in Döbbeler, P. & G. Rambold (eds.). Contributions to Lichenology. Festschrift in Honour of Hannes Hertel. Bibliotheca Lichenologica 88.

Clerc, P. 2004. Usnea, pp. 302-335 in Nash, T.H., III, C. Gries and F. Bungartz (eds.) Lichen Flora of the Greater Sonoran Desert Region, Vol. III. Lichens Unlimited, Arizona State University, Tempe, Arizona, USA.

Clerc, P. 2006. Synopsis of Usnea (lichenized Ascomycetes) from the Azores with additional information on the species in Macaronesia. Lichenologist 38: 191-212.

Clerc, P. 2011. Notes on the genus Usnea Adanson (lichenized Ascomycota). III. Bibliotheca Lichenologica 106: 41-51.

Clerc, P. and M.A. Herrera-Campos. 1997. Saxicolous species of Usnea (lichenized Ascomycetes) in North America. Bryologist 100: 281-301.

Halonen, P., P. Clerc, T. Goward, I.M. Brodo and K. Wulff. 1998. Synopsis of the genus Usnea (lichenized Ascomycetes) in British Columbia, Canada. Bryologist 101: 36-60.

Hinds, J.W. and P.L. Hinds. 2007. Usnea, pp. 487-511 in The Macrolichens of New England. The New York Botanical Garden Press. Bronx, New York, USA.

James, P.W. 2003. Aide mémoire: Usnea. British Lichen Society. 32 pp.

James, P.W., P. Clerc and O.W. Purvis. 2009. Usnea, pp. 918-929 in Smith, C.W., A. Aptroot, B.J. Coppins, A. Fletcher, O.L. Gilbert, P.W. James and P.A. Wolseley (eds.) The lichens of Great Britain and Ireland. Natural History Museum Publications, London, U.K.

Stevens, G.N. 2004. Usneaceae, in McCarthy, P.M. and K. Mallett (eds.) Flora of Australia. Volume 56A, Lichens 4. ABRS/CSIRO Australia, Melbourne, pp. 78-98 & 107-115.

Tavares, I.I. 1997. A preliminary key to the species of California. Bulletin of the California Lichen Society 4: 19-23.

Tõrra, T. and T. Randlane. 2007. The lichen genus Usnea (lichenized Ascomycetes, Parmeliaceae) in Estonia with a key to the species in the Baltic countries. Lichenologist 39: 415-438.


Notes:

The characters to pay close attention to in Usnea are:

1) Is it pendant (“dangly”) or bushy?


U. subscabrosa
pendant

U. trichodea
pendant

U. cavernosa
pendant

U. subfusca
bushy

unknown species
bushy

U. pensylvanica
bushy

2) Is there any red or black coloration on the outside?


U. rubicunda
red cortex

U. rubicunda
red cortex

U. wirthii
red spotted cortex

U. sphacelata?
black cortex

U. sphacelata?
black cortex

3) Is there red or pink coloration inside?


U. ceratina
pink axis

U. ceratina
pink medulla and axis

U. endochrysea
red medulla

4) Are there soredia or isidia?


U. wirthii
soredia


U. ceratina
isidiomorphs

U. hirta
isidia-like fibrils

unknown species
fibrils

U. intermedia
apothecia

5) Do the soredia form tiny spots smaller than half the width of the branch, or large spots greater than half the branch? (But be careful to note small soralia which coallesce into a large mass or irregular soredia toward the branch tips.)


U. subscabrosa
punctate soralia

U. subscabrosa
midsize soralia

U. silesiaca
large soralia

U. subscabrosa
coallescent soralia

6) Are the soralia raised or stipitate, are they flush with the surface, or are the concave and eroded? (Eroded soralia can leave a flap of cortical tissue around the margin.)


U. lapponica
excavate soralia with cortical flap

U. subscabrosa
slightly stipitate soralia

U. wirthii
convex soralia

7) Are the branches, esp. the main branches, goose-bumpy with papillae? (Often variable for any given species.)


U. ceratina
abundant papillae

8) Is the base of the thallus jet-black? (This can be ambiguous.)


U. subscabrosa
pale base

U. ceratina
pale base

U. subfusca
black base

U. silesiaca
black base

9) Is the medulla loose and webby or dense and solid, and is the central axis narrow or very thick? (Loose medulla generally means the secondary branches are constricted like sausages where they attach to the main branches.)


U. silesiaca
thick axis

U. subscabrosa
compact medulla

U. cornuta
lax medulla

10) Are there conspicuous cracks encircling the branches, making it look like it’s made of a string of bones?


U. trichodea
articulate branches

11) Are the branches round in cross-section or angular or pitted or ridged?


U. ceratina
angular branches

U. cavernosa
pitted branches

U. cornuta
constricted branches

U. angulata
winged branches

12) Are there white-topped warts? (There is a subtle variation called a fibercle which has a tiny dot at the tip formed by a secondary branch breaking off leaving a scar where the central axis used to be.)


U. ceratina
tubercles

Of course, different species grow on rock and trees. And spot tests on the medulla are extremely helpful for verification, especially when still learning what all these characters really mean: lye (K) and bleach (C) are mostly all that are needed for Usnea, but occasionally also paraphenylenediamine (P) and UV light (350 nm).


U. ceratina
diffractaic acid (CK+o)

Description author: Jason Hollinger (Request Authorship Credit)


Created: 2008-11-05 20:31:13 CST (-0500) by Jason Hollinger (jason)
Last modified: 2012-03-19 14:45:49 CST (-0500) by Jason Hollinger (jason)
Viewed: 874 times, last viewed: 2018-06-21 16:55:14 CDT (-0400)