Assessment Synopsis – Cetradonia linearis is a fruticose species that grows on rock outcrops and boulders and is narrowly endemic to the southern Appalachians. This species is threatened by habitat degradation due to invasive tree pests, climate change and resource extraction. Continued protection under the Endangered Species Act is required to ensure that this species does not decline.
Distinguishing Traits – The Rock Gnome Lichen looks like patches of small green fingers (squamules) growing out from rock outcrops and boulders. It is often fertile and bears black apothecia at the ends of the podetia. The podetia are solid, and occasionally branched.
Explanation of Chosen Red List Category and Criteria – This species warrants listing as Vulnerable under criterion C1. There are ~4,000 mature individuals documented throughout the range of Cetradonia linearis. The number of mature individuals was calculated from element occurrence records held by national forests, natural heritage programs, and national parks from throughout the range of the species. A mature individual was considered a distinct colony that is producing apothecia.
A generation time for this species is estimated to be 33 years, so three generations is a total of 99 years. A minimum 10% decline is projected for this species within the next three generations due to acombination of 1) Abies fraseri mortality caused by the Balsam Wooly Adelgid and climate change (Farjon 2013a), 2) Tsuga canadensis mortality caused by the Hemlock Woolly Adelgid (Farjon 2013b), and 3) climate change impacting cloud immersion regimes for high-elevation subpopulations (Cullataand Horton 2014).
Assessor/s: Allen, J., Lendemer, J. & McMullin, T.; Reviewer/s: Scheidegger, C.
Culatta, K.E. & Horton, J.L. (2014) Physiological Response of Southern Appalachian High-Elevation Rock Outcrop Herbs to Reduced Cloud Immersion. Castanea79: 182-194.
Farjon, A. (2013) Abies fraseri. In The IUCN Red List of Threatened Species Version 2015.2. Available at: www.iucnredlist.org. (Accessed: 06 July 2015).
Farjon, A. (2013) Tsuga canadensis. In The IUCN Red List of Threatened Species Version 2015.2. Available at: www.iucnredlist.org. (Accessed: 06 July 2015).
IUCN (2015) The IUCN Red List of Threatened Species. Version 2015-4. Available at: www.iucnredlist.org. (Accessed: 19 November 2015).
Krapfl, K.J., Holzmueller, E.J. & Jenkins, M.A. (2011) Early impacts of hemlock woody adelgid in Tsuga canadensis forest communities of the southern Appalachian Mountains. Bulletin of the Torrey Botanical Club138(1): 93-106.
Rollins, A.W., Adams, H.S. & Stephenson, S.L. (2010) Changes in forest composition and structure across the red spruce-hardwood ecotone in the central Appalachians. Castanea75: 303–314.
Rose, A. & Nicholas, N.S. (2008) Coarse woody debris in a Southern Appalachian spruce-fir forest of the Great Smoky Mountains National Park. Nat. Areas J.28: 342–355.
White, P.B., van de Gevel, S.L. & Soulé, P.Y. (2012) Succession an disturbance in an endangered redspruce-Fraser fir forest in the southern Appalachian Mountains, North Carolina, USA. Endangered Species Research18: 17-25.
Find out more about the IUCN Red List Categories and Criteriahere.
TYPE. UNITED STATES. TENNESEE, Sevier County, Roaring Fork, Mt. LeConte, 25.VI.1933, K. Baur & M. Fulford 39 (US, holotype).
Description. Lichenized fungus.
Thallus fruticose, forming dense colonies of narrow straps (squamules) up to 2 square meters. Primary squamules 10-15 x 0.5-1 mm, widest at tip,irregularly branched, sublinear, sinuous, rounded, loosely aggregated, dark greenish mineral gray above, pale below, cortical layer above and below continuous; base blackened. Squamules grow parallel to the rock surface but curl up and outward at the tip. Photobiont trebouxioid alga. Podetia arising from the margin of the primary thallus, short or abortive, about 0.7 mm. thick, cylindrical, simple, aseypha, pale, solid (without cavity), continuous cortical layer about 0.15 mm. thick. Ascomata biatorine apothecia, solitary or aggregated atop of podetia, 0.1-1 mm. wide, brownish or brownish-black; ascospores oblong 8 x 3 μm.