Trapeliopsis bisorediata is a severely fragmented soil crust species. It is known from 6-9 scattered subpopulations from Washington, Oregon, Idaho, and California. A subpopulation in Washington appears to be stable while subpopulations in Idaho are declining due to overgrazing and wildfires. Soil crusts are usually delicate and do not respond well to disturbances. The species warrants a rank of Endangered, B2ab(i,ii,iii,iv) based on an area of occupancy of 152 km2, severely fragmentation, and inferred declines due to overgrazing, wildfires, and urban and commercial development.
Assessor/s: Reese Næsborg, R., Root, H. & Stone, D.; Reviewer/s: Allen, J.
Armstrong, A., Ostle, N.J. & Whitaker, J. (2016) Solar park microclimate and vegetation management effects on grassland carbon cycling. Environmental Research Letters11: 074016.
Condon, L.A., Pietrasiak, N., Rosentreter, R. & Pyke, D.A. (2020) Passive restoration of vegetation and biological soil crusts following 80 years of exclusion from grazing across the Great Basin. Restoration Ecology28: S75-S85.
IUCN (2022) The IUCN Red List of Threatened Species. Version 2022-1. Available at: www.iucnredlist.org. (Accessed: 21 July 2022).
McCune, B., Camacho, F., & Ponzetti, J. (2002) Three new species of Trapeliopsis on soil in western North America. The Bryologist105: 78-85.
Find out more about the IUCN Red List Categories and Criteriahere.
Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: forming a mosaic of densely crowded, rather thick areoles areoles: flat-topped to hemispherical, closely appressed to the substrate, 0.1-0.7(-1) mm in diam. surface: white to pale gray pruinose or brownish in epruinose spots, sorediate soralia: of two types, (1) diffuse, poorly delimited, with fine soredia of the same color as the thallus, (2) rounded and well-defined, often in the center of areoles, up to 0.5 mm in diam., containing dark brown to black soredia cortex: 10-20 µm thick, composed of hyaline hyphae but often abraded and lacking algal layer: 35-60 µm thick medulla: not delimited against the substrate photobiont: 5-12 µm in diam. Apothecia: not seen, but occasionally with some abortive, marginal apothecia-like structures with hollowed out or sorediate centers Spot tests: thallus K-, P-, C+ red, KC+ red, UV- Secondary metabolites: gyrophoric acid. Substrate and ecology: on soil in shrub steppe (especially Artemisia tridentata) and grasslands World distribution: primarily known only from the semi-arid region between the Rocky Mountains and Cascade Range (Oregon, Washington, Idaho) and also southern California Sonoran distribution: southern California. Notes: Among the Sonoran species of Trapeliopsis, T. bisorediata is characterized by its two types of soralia. Within the area, it can only be confused with T. steppica, which has a darker gray, less pruinose thallus, that is squamulose rather than areolate. The soralia in Trapeliopsis steppica are uniformly dark and tend to be marginal rather than central in the areoles.