TYPE. INDIA. Madras [Tamil Nadu, Chennai]. R. Wight s.n. (FH, lectotype designated by Hale 1974; BM BM000006420, G, isolectotypes; H H-NYL 22483, type).
Description.Life form: lichenized fungus.
Thallus crustose, pale greenish mineral gray, thick and epiphloeodal, bulging (gall-forming); surface smooth but grainy in appearance; hypothallus black. Cortex loose; photobiont trentepohlioid alga in layer with columnar calcium oxalate crystals; medulla loose with scattered clusters of red crystals. Ascomata pore-like apothecia, immersed, 0.1-0.3 mm diam., disk covered by a round pore, 0.05-0.20 mm in diam.; margin entire, gray-brown. Columella absent; exciple not carbonized, pale brown; paraphysoids absent; hymenium clear, 100-150 μm high; paraphyses unbranched but anastomosing laterally towards the excipulum. Asci 8-spored; ascospores brown, submuriform with 4-6 transverse locules and 0-2 longitudinal locules, 20-30 x 9-13 μm with thickened septa and rounded lumina, I+ violet-blue.
Chemistry. Unidentified red anthraquinone pigment in medulla.
Substrate and Habitat. Corticolous on trees, less frequently on mosses, commonly found on shaded to semi-exposed tree trunks in forests.
Distribution. Pantropical, north into southeastern North America and Europe; in North Carolina found in the Coastal Plain and Piedmont ecoregions.
Notes. The inflated gall-forming thallus cavity is often inhabited by ants.
Hale, M.E., Jr (1974) Morden-Smithsonian Expedition to Dominica: The lichens (Thelotremataceae). Smithsonian Contributions to Botany16: 1-46 (description as Leptotrema wightii).
Lücking, R., A. Mangold, A., E. Rivas Plata, S. Parnmen, E. Kraichak & H.T. Lumbsch (2015) Morphology-based phylogenetic binning to assess a taxonomic challenge: A case study in Graphidaceae (Ascomycota) requires a new generic name for the widespread Leptotrema wightii. Botanical Journal of the Linnean Society179(3): 436-443.
Sipman, H.J.M., R. Lücking, A. Aptroot, K. Kalb, J.L. Chaves, & L. Umana (2012) A first assessment of the Ticolichen biodiversity inventory in Costa Rica and adjacent areas: the thelotremoid Graphidaceae (Ascomycota: Ostropales). Phytotaxa55: 1-214.
Taylor, T. (1847) New lichens, principally from the Herbarium of Sir William J. Hooker. London Journal of Botany6: 148-197 (original description as Endocarpon wightii).