The rock gnome lichen is one of two lichens in the United States protected by the Endangered Species Act.  Lichens are two organisms, a fungus and alga or cyanobacterium that exist so closely in a symbiotic relationship they are functionally a single organism. The alga or cyanobacterium provides nutrients to the fungus and the fungus in turn provides a protected and secure environment for the alga or cyanobacterium to live. Rock gnome lichen is in the reindeer moss family, actually a family of lichens, not mosses.

The rock gnome lichen was placed on the federal threatened and endangered species list, as endangered, in 1995, when there were 32 known populations, all in North Carolina or Tennessee. That number has steadily increased as new populations have been discovered, and today there are 68, 62 of which are in conversation ownership. Being in conservation ownership protects the habitat from development, but the lichen still faces impacts from climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.

Learn more about climate change , outdoor recreation, collection, and habitat degradation from the balsam woolly adelgid.

• U.S. Fish and Wildlife Service. 1997. Recovery Plan for Rock Gnome Lichen (Gymnoderma lineare)(Evans) Yoshimura and Sharp. Atlanta, GA. 30 pp.
• 2019 Five-year review

Habitat

The rock gnome lichen is found in the Southern Appalachian Mountains on vertical rock faces either at foggy high elevation areas or in deep gorges in lower elevations, both areas of high humidity.  It appears the species needs a moderate amount of light but cannot tolerate too much sun intensity.  It does well on generally open sites with a northern exposure that are moist and where the seepage water from the forest soils above only flows during very wet times.

The rocks on which this lichen grows are of several types, including igneous, metamorphic, and metasedimentary rocks such as quartz diorite, garnet-rich biotite, muscovite and quartz schist, quarts phyllite, metagraywacke, metaconglomerte, and metakoses containing feldspar and cholrite, amphibole, hornblende, and feldspar gneiss. 

• U.S. Fish and Wildlife Service. 1997. Recovery Plan for Rock Gnome Lichen (Gymnoderma lineare)(Evans) Yoshimura and Sharp. Atlanta, GA. 30 pp.
• North Carolina Natural Heritage Program. 2019. Element Occurrence records and scorecard for Gymnoderma lineare. Print date October 1, 2019.
• Massey, J.P. Whitson, and T. Atkinson. 1980. Endangered and threatened plant survey of 12 species in the eastern part of Region IV. USFWS Contract 14-160004-78-108 Report.

Food

Lichens do not have roots that absorb water and nutrients as plants do, but like plants, the alga or cyanobacterium component of lichens produce their own nutrition by photosynthesis, using sunlight to create food from carbon dioxide and water.

Physical characteristics

Rock gnome lichen grows in dense colonies of narrow strap-like lobes that grade from black at the base to blue-gray on the upper surface and white on the lower surface. 

• U.S. Fish and Wildlife Service. 1997. Recovery Plan for Rock Gnome Lichen (Gymnoderma lineare)(Evans) Yoshimura and Sharp. Atlanta, GA. 30 pp.

Reproduction

The primary means of propagation appears to be asexual, with colonies spreading clonally.

• U.S. Fish and Wildlife Service. 1997. Recovery Plan for Rock Gnome Lichen (Gymnoderma lineare)(Evans) Yoshimura and Sharp. Atlanta, GA. 30 pp.

Geography

When the species was federally listed in 1995, the listing rule recognized extant populations in 10 counties in North Carolina (Ashe, Avery, Buncombe, Haywood, Jackson, Mitchell, Rutherford, Swain, Transylvania, and Yancey) and one county in Tennessee (Sevier). By 2012, the species range expanded to include Burke, Graham, and Macon Counties in North Carolina, Rabun County in Georgia, Greenville County in South Carolina, Carter County in Tennessee, and Smyth County in Virginia. A new county record of rock gnome lichen was observed in Clay County, North Carolina in 2014.

• U.S. Fish and Wildlife Service. 1995. Gymnoderma lineare (Rock Gnome Lichen) Determined to be Endangered. Federal Register 60(11) 3557 – 3562.
• North Carolina Natural Heritage Program. 2012. Element Occurrence scorecard for Gymnoderma lineare. Print date November 19, 2012.
• Hodges, M. 2019. The Nature Conservancy in Georgia, Atlanta, GA. Gymnoderma lineare data. Personal communication, email dated April 30, 2019.
• South Carolina Heritage Trust Program. 2019. Element Occurrence record for Gymnoderma lineare. Data received October 18, 2019.
• North Carolina Natural Heritage Program. 2019. Element Occurrence records and scorecard for Gymnoderma lineare. Print date October 1, 2019.
• Van Alstine, N. 2015. A 2014 Survey for Cetradonia linearis (Evans) J.-C. Wei & Ahti (Rock Gnome Lichen) in Virginia – Natural Heritage Technical Report 15-03. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, VA. 15pp with appendices.