Diagnosis: Similar to Herpothallon granulare, but containing confluentic acid, brialmontin 1 and brialmontin 2 instead of perlatolic acid; typically saxicolous, very rarely corticolous.
Type: Ecuador. Galapagos Islands: Isla Santiago, along the trail from the caseta in La Central to La Bomba (at the coast), cliff ca. 2.5 km NE of the caseta, 0°13’41”S, 90°44’10”W, alt. 533 m, transition zone, SW-exposed basalt cliff with some ferns (Adiantum concinnum, Pityrograma calomelanos var. calomelanos, and Blechnum polypodioides) growing in crevices, on horizontal ledges of SW-exposed front of basalt cliff; semi-shaded, wind- and rain-exposed, 25-Mar-2008, Bungartz 4874 (CDS 29073-holotype).
Thallus saxicolus, delimited by a broad prothallus of white arachnoid hyphae that soon aggregate into loosely radiating fibrous strands; thallus surface dull greenish to beige, with storage becoming ±white, ecorticate, entire thallus initially of loosely interwoven hyphae that soon form distinct fibrous strand and with age rarely become more densely interwoven and almost cottony, typically not developing into a distinctly differentiated thallus, but instead covered with abundant, coarsely granular pseudisidia; medulla poorly differentiated, indistinct, with hyphae covered by colorless to pale brownish granules, lacking calcium oxalate crystals (not forming colorless, needle-shaped crystals in 25% H2SO4); asci and pycnidia not observed.
Distribution and ecology: Currently known only from Galapagos and very likely endemic; moderately common throughout the dry and lower transition zone, rarely extending into the humid zone; on sheltered, shaded rock faces and overhangs.
Notes: Morphologically this new species closely resembles H. granulare, but it is chemically distinct and is not corticolous, instead growing on sheltered rock surfaces. When the material was first analyzed in solvent C, specimens were believed to represent a K+ yellow chemotype of H. granulare that contained atranorin in addition to perlatolic acid. However, in solvent A, the specimens were shown to contain confluentic acid and brialmontin 1 and brialmontin 2 (the latter two substances have almost identical Rf to atranorin in solvent C).
The only other species of Herpothallon known to contain related substances (brialmontic acid, methylbrialmontic acid, and dimethylbrialmontic acid) is H. brialmonticum Aptroot & Elix. This corticolous species is morphologically dissimilar from H. granulare, forming a much more compact, thick, cottony thallus with smoother, globose pseudisidia. In contrast, H. saxorum is composed of fibrous hyphal strands with rather coarse, distinctly granular pseudisidia.
Specimens examined: Ecuador: Galapagos: Isla Santa Cruz, along the road from Bellavista to Los Gemelos, 0°38’10”S, 90°23’45”W, alt. 579m, humid zone, open Scalesia pedunculata forest with Rubus niveus, Psychotria rufipes, Zanthoxylum fagara, and scattered lava boulders, on rock of top and slope of basalt boulders; semi-shaded, wind- and rain-sheltered, 12-Feb-2006, Bungartz 3470 B (CDS 27226); above Mina Granillo Rojo on the N-side of the island, 0°37’9”S, 90°21’57.73”W, alt. 619m, transition zone, upper transition zone; open forest of Scalesia pedunculata, Psidium galapageium, Zanthoxylum fagara and few Pisonia floribunda with basaltic rock outcrops, on rock of N-exposed overhang of basalt boulder; semi-shaded, wind- and rain-sheltered, 07-Aug-2008, Bungartz 8111 (CDS 40757); Isla Isabela, Volcán Darwin, Isabela, southwestern slope, above Tagus Cove, 0°13’28.19”S, 91°19’17.89”W, alt. 872m, transition zone, top of lava flow in open scrubland of Croton scouleri and Dodonaea viscosa with Cordia revoluta and some Opuntia insularis, on rock of S-exposed overhang of basalt boulder; shaded, wind- and rain-sheltered, 15-Nov-2007, Bungartz 7740 (CDS 38246); southwestern slope, above Tagus Cove, 0°13’59”S, 91°20’8”W, alt. 597m, dry zone, open Bursera graveolens forest with Croton scouleri and Macraea laricifolia shrubs, few Chiococca alba and Scalesia microcephala, among lava boulders and outcrops, on rock of SW-exposed overhang of basalt boulder; shaded, wind- and rain-shaded, 16-Nov-2007, Bungartz 7803 (CDS 38312); Bungartz 7793 (CDS 38302); Volcán Sierra Negra, Muro de las Lagrimas W of Puerto Villamil, along the stairs going up behind the wall, 0°57’52.73”S, 91°0’46.79”W, alt. 78m, dry zone, dry zone vegetation with Bursera graveolens and Opuntia echios, slope 45° N, on rock of basaltic rocks at the side of the stairs, 17-Aug-2008, Herrera-Campos, M.A. 10745, (CDS 40483).
from: Bungartz, F., Dútan, V. & Elix, J.A. (2013) The lichen genera Cryptothecia, Herpothallon and Helminthocarpon (Arthoniales) in the Galapagos Islands, Ecuador. The Lichenologist45(6): 1–24.