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Cetradonia linearis (Evans) Wei & Ahti
Rock Gnome
Federal Protection: Listed Endangered
State Protection: Endangered
Global Rank: G3
State Rank: S1
Element Locations Tracked in Biotics: Yes
SWAP High Priority Species (SGCN): Yes
Element Occurrences (EOs) in Georgia: 1
Habitat Summary for element in Georgia: Wet north-aspect, high-elevation cliff
Grows in dense colonies made up of many narrow, strap-shaped, sometimes once-branched squamules 1 - 2 cm long & less than 1 mm wide; upper surface of the lobes is dark blue-gray grading to black at the base; lower surface is glossy white; lobes grow down along rock surface then curl up & outward at the tip; black or dark brown apothecia, less than 1 mm wide, develop on the tips & occasionally on sides of the lobes; FIELD ID: unmistakable
Squamules of Cladonia are never as long; podetia of Cladonia, e.g., C. subcariosa, may be mistaken for this species, but they grow up, are always round & hollow, & are not two-sided
None
Moist, high-humidity, rocky cliff faces at highest elevations, usually shaded, often growing with the mosses Andreaea or Grimmia
Saxicolous squamulose lichenized fungus, photobiont a green alga (Trebouxia?)
Surveys may be conducted all year
Rare, endemic to the Southern Appalachians of Ga., S.C., N.C., Tenn. & Va.
Trampling by climbers & hikers, soil erosion, unauthorized & excessive collection; development of nearby habitat; removal of canopy for trails or other recreational uses; logging or other tree removal near populations; air pollution; drying due to loss of tree canopy due to disease or insect infestation; elevated temperatures & droughts due to climate change
Ranked S1, listed as Endangered by Ga. & U.S. Fish & Wildlife Service; 1 population has been documented in Ga. on protected land
Protect sites from collectors, climbers, & hikers; prevent logging, clearing, & trail or other construction in the vicinity of populations; monitor populations for effects of climate change
Brodo, I.M, S.D. Sharnoff, and S. Sharnoff. Lichens of North America. Yale University Press, New Haven, Connecticut.
Chafin, L.G. 2007. Field guide to the rare plants of Georgia. State Botanical Garden of Georgia and University of Georgia Press, Athens.
Esslinger, T. L. 2006. A cumulative checklist for the lichen-forming, lichenicolous and allied fungi of the continental United States and Canada. North Dakota State University. http://www.ndsu.nodak.edu/instruct/esslinge/chcklst/chcklst7.htm
NCNHP. 2001. Guide to federally listed endangered and threatened species of North Carolina. North Carolina Natural Heritage Program, Raleigh, North Carolina. https://digital.ncdcr.gov/digital/collection/p249901coll22/id/505870
NatureServe. 2020. Cetradonia linearis, Rock Gnome Lichen species account. NatureServe Explorer. Arlington, Virginia. https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.124874/Cetradonia_linearis
Reid, R. 2011. Rock Gnome Lichen (Gymnoderma lineare) species accont. U.S. Fish and Wildlife Service, Washington, D.C. https://www.fws.gov/raleigh/species/es_rock_gnome_lichen.html
Sharnoff, S. [n.d.] Cetradonia linearis images. http://www.sharnoffphotos.com/lichens/cetradonia_linearis.html
Sharnoff, S. [n.d.] Lichen natural history. http://www.sharnoffphotos.com/lichensNH/lichen_natural_history.html
USFWS. 2019. Rock Gnome Lichen (Gymnoderma lineare) species profile and related documents. U.S. Fish and Wildlife Service. https://ecos.fws.gov/ecp0/profile/speciesProfile?sId=3933
Weakley, A.S. 2015. Flora of the southern and mid-Atlantic States. University of North Carolina Herbarium, University of North Carolina, Chapel Hill. http://www.herbarium.unc.edu/flora.htm
Yoshimura, I. and A.J. Sharp. 1968. A revision of the genus Gymnoderma. American Journal of Botany 55(5): 635-640. https://bsapubs.onlinelibrary.wiley.com/doi/abs/10.1002/j.1537-2197.1968.tb07422.x
Linda G. Chafin
L. Chafin, Oct. 2007: original account.
K. Owers, Jan. 2010: updated status and ranks, added pictures.
L. Chafin, Jun. 2020: updated original account.
