Species Fact Sheet s3
SPECIES FACT SHEET
Common Name: Chalk foam, snow lichen
Scientific Name: Stereocaulon spathuliferum
Division: Ascomycota
Class: Ascomycetes
Order: Lecanorales
Family: Stereocaulaceae
Technical Description: Plants fruticose. Thallus crustose, granular, disappearing with age. Fruiting stalks (pseudopodetia) white, erect, conspicuous with spreading branches, branches thickened basally, round or flattened, 30-50 mm tall, mostly lacking a cortex and tomentum, not woody, tightly attached to substrate, the tips thickly covered with soredia; leaf-like phyllocladia on pseudopodetia sessile, flattened, chalky white to bluish-gray, spoon-shaped, 0.3-3 mm wide, apices rounded or upturned, usually partly corticate dorsally and partly sorediate, the soredia diffuse and often more abundant ventrally. Cephalodia on pseudopodetia bluish or brownish, stalked, densely branched, containing Stigonema. Apothecia at tips of branches, to 3 mm wide, convex. Thallus P+ orange, phyllocladia and soredia K+ yellow and PD+ orange, with atranorin, stictic and norstictic acids. Stereocaulon spathuliferum forma pygmaeum is the only form in the Pacific Northwest. Distinctive characters: (1) Phyllocladia partly corticate and partly sorediate, (2) phyllocladia PD+ orange, (3) pseudopodetia firmly attached to rocks, (4) alga Stigonema instead of Nostoc. Similar species: Stereocaulon vesuvianum has peltate phyllocladia and no soredia. Stereocaulon botryosum has Nostoc in its cephalodia instead of Stigonema, is PD+ pale yellow or PD-, and does not contain stictic acid. Other descriptions and illustrations: Clayden & Goward 1999: 237; McCune & Geiser 1997: 274; McCune & Goward 1995: 161; Thomson 1984: 424.
Life History: Details for this species are not documented. The thallus is at first granular but disappears with age. Most of the plant body consists of pseudopodetia, firmly attached to substrate.
Range, Distribution, and Abundance: Circumboreal. In the Pacific Northwest, Alaska south to Oregon, in and west of the Cascade Range.
Documented on: National Forests: Willamette.
Rare, probably undercollected.
Habitat Associations: Forming small crusts on basalt blocks of talus slopes, shaded to partially exposed, usually sheltered from precipitation but requiring seasonally cool and moist conditions. Elevation 3000 to 5000 feet. Forest types are Abies amabilis, Tsuga heterophylla, and Pseudotsuga menziesii associations.
Threats: Rock climbing, road and trail construction, and global warming are possible threats. Populations are small, discontinuous, widely scattered, making them vulnerable to local extinction. Rock outcrops and talus slopes are common in the Pacific Northwest but microsites for Stereocaulon spathuliferum are often lacking for reasons unknown.
Conservation Considerations: Consider managing known sites at least until more is known about Stereocaulon spathuliferum. Buffers around outcrops and talus slopes in the vicinity of Stereocaulon may help maintain needed microclimate.
Preparer: John A. Christy
Date Completed: May 2006
Edited by: Rob Huff
Date: July 5, 2007
References
Clayden, S.R. & T. Goward. 1999. Stereocaulon. Pp. 227-239 in: Goward, T. The Lichens of British Columbia. Part 2. Fruticose species. British Columbia Ministry of Forests Research Program. 319 pp.
Lamb, I.M. 1977. A conspectus of the lichen genus Stereocaulon (Schreb.) Hoffm. Journal of the Hattori Botanical Laboratory 43: 191-355.
McCune, B. & L. Geiser. 1997. Macrolichens of the Pacific Northwest. Oregon State University Press, Corvallis. 386 pp.
______& T. Goward. 1995. Macrolichens of the Northern Rocky Mountains. Mad River Press, Arcata, California. 208 pp.
Oregon Natural Heritage Information Center. 2004. Rare, threatened and endangered species of Oregon. Oregon Natural Heritage Information Center, Oregon State University. Portland. 104 pp. http://oregonstate.edu/ornhic/2004_t&e_book.pdf
Thomson, J.W. 1984. American Arctic Lichens. 1. The Macrolichens. Columbia University Press, New York. 504 pp.
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