Lecanora subimmersa (Fée) Vain. (1890: 98) MycoBank no. 389345 Type:— BRASIL. RIO DE JANEIRO: exact locality unknown, 1869, Glaziou, A.F.M. 3294 (M– isotypes). (Fig. 3E–F) Thallus saxicolous, thick, contiguous, rimose-areolate, fissures with distinctly crenate to strongly serrate, tightly interlocking edges; surface white to creamish beige, smooth to ±roughened, epruinose, lacking soredia; prothallus a thin compact, blackened line, most pronounced where different thalli meet. Apothecia sparse to numerous, circular, 0.1–1 mm in diam., cryptolecanorine, immersed, not emerging, with a plane to slightly depressed, epruinose disc, margin not or barely differentiated from the surrounding thallus; hymenium hyaline, not inspersed, epihymenium lacking crystals, with a diffuse reddish brown pigment (arnoldiana -brown: K+ dull brown, HCl+ reddish brown, N−), pigment persistent in K (glabrata - type); proper exciple thin, rarely moderately developed and then with diffuse reddish brown pigment (arnoldiana -brown), with few crystals; thalline exciple barely differentiated from surrounding thallus, with few large crystals that do not dissolve in K (± pulicaris - type); hypothecium hyaline to pale yellowish (intensifying in K); ascospores 8/ascus, simple, narrowly to broadly ellipsoid, (6.9−)9.7− 13.4(−14.9) × (5.0−)4.3−6.1(−5.9) µm (n = 22). Pycnidia not seen [according to Ryan et al. (2004): immersed, conidia filiform 15−18 µm long]. Chemistry: Two chemotypes are known; see the two subspecies below. Ecology and distribution: A pantropical species, reported by Guderley (1999) from Central America and tropical South America. Guderley (1999) previously reported only L. subimmersa ssp. subimmersa; here we also report the other chemotype (but see comments below); although generally widely distributed, this species is not common in Galapagos, where very few specimens have been collected in the dry and transition zone, growing with other, morphologically very similar species, L. austrosorediosa, L. legalloana, L. prosecha and Caloplaca diplacia. Notes: When well developed, L. subimmersa can readily be recognized by its areoles that appear interlocked by their strongly serrate margin and the deep brown, immersed apothecia. Superficially it is extremely similar to L. prosecha and L. legalloana, which, when well developed, occasionally also form thalli with serrate fissures and closely interlocking areoles, but L. legalloana can reliably be distinguished by its deep orange, K+ strongly purple lower medulla, and the xanthones of L. prosecha are different from those of L. subimmersa ssp. ramboldii. Lecanora prosecha is also the only species that is known to occasionally produce soralia. All three taxa are obviously very closely related and could perhaps better be treated as different chemotypes. Not one of the three taxa has an N+ reddish violet pigment present in the epihymenium, unlike L. oreinoides, which is similar because of its immersed apothecia, but never forms serrate, interlocked areoles. In the Galapagos L. subimmersa and L. oreinoides appear to be the least common species among these four similar taxa. All grow in close proximity, often in the same habitats and may often be collected together. Guderley (1999) included L. subimmersa in the L. subfusca -group, probably because its disc is not strongly blackened and it generally lacks the aeruginose, N+ purple or reddish violet apothecial pigment present in the other species of the L. marginata -group. However, the morphology and anatomy of this species suggests that it may be better placed together with L. avium, L. oreinoides and L. legalloana, i.e., in the L. marginata -group.

Published as part of Bungartz, Frank, Elix, John A. & Printzen, Christian, 2020, Lecanoroid lichens in the Galapagos Islands: the genera Lecanora, Protoparmeliopsis, and Vainionora (Lecanoraceae, Lecanoromycetes), pp. 1-85 in Phytotaxa 431 (1) on page 18, DOI: 10.11646/phytotaxa.431.1.1, http://zenodo.org/record/13877123