Diagnosis. Differs from Pertusaria tejocotensis var. tejocotensis B. de Lesd. by the presence of stictic acid and related metabolites.
Type. ECUADOR. GALAPAGOS ISLANDS: Isla Pinzón, E-facing side of a valley on the W-slope of the highest mountain, 0°36'49''S, 90°40'14''W, 294 m alt., transition zone, E-facing basalt cliff and Scalesiabaurii ssp. baurii; Polypodium tridens growing on the basalt cliff, on top and flat slope of sunny, wind- and rain-exposed basalt boulder, 16 Feb 2006, Bungartz 3608 (CDS27426, holotype).
Description. Thallus saxicolous, crustose, rimose-areolate; surface pale to deep lemon-yellow, dull to ±shiny, smooth, epruinose, plane to barely wrinkled, lacking soredia or isidia; medulla white; margin not distinctly zonate, not delimited by a distinct prothallus. Apothecia verruciform, hemispherical to subglobose, 0.5-0.7(–1.2) mm diam., single or rarely fusing, constricted at the base, apically not flattened, concolorous with the thallus, mono- to polycarpic, with 1–2(–4) dark brownish to blackish grey or jet black, punctiform ostioles, not delimited by a distinct rim, single or rarely fusing, plane to ±sunken, or emerging as small papillae on top of the apothecial verrucae; thalline exciple hyaline, lacking large crystals, but with abundant minute crystals (dissolving in K, re-forming as yellowish clusters of needle shaped crystals; thiophaninic acid), cortex lacking crystals; epihymenium dull brown, K–; proper exciple and hypothecium hyaline to pale yellowish, not inspersed with crystals; hymenium not inspersed, of branched and sparingly anastomosing hyphae, ±loosely intertwined around asci; asci cylindrical, (2–)4–6(–8)-spored; ascospores hyaline, ellipsoid to broadly fusiform or ±citriform, (49–)54–74(–80) μm long, (22–)28–37(–42) μm wide (n = 20); spore wall 2-layered, outer wall 2–3(–5) μm thick, with conspicuous microrugulate ornamentation, inner wall (3–)4–5 μm wide, with maturity distinctly laminated, markedly thickened apically (to 12 μm); pycnidia not seen.
Distribution and ecology. This is the most common taxon on rock in the Galapagos, particularly on sunny, wind- and rain-exposed boulders and cliffs in the dry and transition zones, generally found in dry habitats from the coast to the high altitude dry zone. Pertusaria tejocotensis var. tejocotensis is known from Mexico and south-western USA (Lumbsch and Nash 2002, Dibben 1980).
Notes. The stictic acid chemosyndrome is here reported for the first time from P. tejocotensis s. lat. It was previously considered a good diagnostic character to distinguish this species from the morphologically similar P. texana. Both species contain thiophaninic acid as a major xanthone, but P. tejocotensis contains additional confluentic and 2'-O-methylperlatolic acid, both absent in P. texana. However, the two species are clearly distinguished by their substrate preferences. Pertusaria texana grows on bark or rarely on wood, whereas P. tejocotenis typically inhabits rock, rarely soil or detritus (one specimen was found to be parasitic on Stereocaulonazulense). In both species the number of ascospores per ascus varies, but the asci of P. tejocotensis most commonly contain four, rarely six to eight ascospores. In P. texana asci are typically 8-spored, although they occasionally may produce fewer ascospores. Both species have two-layered spore walls with the inner wall thickened apically, but in P. tejocotensis the inner wall appears distinctly laminated. These laminations are not observed in P. texana.