Lecanora cactacea Bungartz & Elix, 2020

Bungartz, Frank, Elix, John A. & Printzen, Christian, 2020, Lecanoroid lichens in the Galapagos Islands: the genera Lecanora, Protoparmeliopsis, and Vainionora (Lecanoraceae, Lecanoromycetes), Phytotaxa 431 (1), pp. 1-85 : 40-42

Lecanora cactacea Bungartz & Elix sp. nov. MycoBank no. 833371

Diagnosis. Superficially similar to Lecanora subcrenulata , characterized by a similar chemistry, but very different apothecial anatomy [epihymenium yellowish brown, not soluble in K, lacking crystals (glabrata - type), the exciple abundantly filled with fine crystals soluble in K, lacking larger crystals (allophana - type)].

Type:— ECUADOR. GALAPAGOS: Isabela, Volcán Sierra Negra, Volcán Chico on the northeastern slope of Sierra Negra, 0˚46’56.77’’ S, 91˚6’4.298’’W, 938 m alt., transition zone, young lava flow with very scattered vegetation ( Macraea laricifolia , Darwiniothamnus tenuifolia ), on SW-exposed trunk of Jasminocereus thouarsii , 14-Aug-2008, Bungartz, F. 8178 ( CDS 40824– holotype).

( Fig. 13C–D )

Thallus corticolous (on cacti, Jasminocereus ), thin and in parts ±discontinuous, rimose-areolate to verrucose areolate; surface white to pale gray, strongly roughened, matt, epruinose or with faint, whitish pruina, lacking soredia; prothallus white, weakly developed, often indistinct. Apothecia sparse to numerous, typically ±isolated or a few aggregating, circular to very irregular in outline, often quite large, 0.5–1.7(–2.2) mm in diam., soon sessile and conspicuously constricted at the base, distinctly lecanorine, margin persistent, conspicuously fissured, often broadly undulating and at least in parts ±crenate, epruinose, concolorous with the thallus, disc deeply concave to ±plane, pale beige to brown, darkening with age (due to parasitic fungi), occasionally almost blackened, epruinose; hymenium hyaline, not inspersed, epihymenium lacking crystals, with a diffuse yellowish brown pigment (cf. leptocline -brown: turning orange in K, forming a yellowish solution, HCL+ intensely brown, N−), pigment not soluble in K, (cf. glabrata - type), proper exciple thin, indistinct, with abundant small crystals, thalline exciple thick, ±corticate, filled with abundant small crystals that are completely soluble in K (allophana - type); subhymenium and hypothecium hyaline; ascospores 8/ascus, simple, broadly ellipsoid to subglobose, (5.9–)6.2–8.0(–8.8) × (4.9–)5.1–6.0(–6.4) µm (n = 20). Pycnidia not seen.

Chemistry: Thallus cortex including apothecial margin P+ yellow, C−, KC−, K+ yellow, UV−; with atranorin [major], isonotatic acid [major], 4- O -methylhypoprotocetraric acid [minor], norisonotatic acid [minor], and 2’- O - methylperlatolic acid [major]; [all specimens cited were analyzed with TLC].

Etymology: Growing on cacti ( Jasminocereus ).

Ecology and Distribution: Known only from Galapagos, where relatively few specimens have been found on the columnar, endemic cactus, Jasminocereus thouarsii .

Notes: Lecanora cactacea is morphologically very similar to L. subcrenulata and the two species share the same chemistry. However, they are anatomically distinct, as the thalline exciple of L. cactacea is entirely filled with small crystals. In L. subcrenulata the exciple may appear densely filled by small crystals, but when K is applied the small crystals rapidly dissolve to reveal a few larger crystals.

The thalli of L. cactacea and Pertusaria oahuensis H. Magn. are superficially extremely similar. A specimen of P. oahuensis collected growing side by side on Jasminocereus (Bungartz 8176, CDS 40822), was initially believed to be the sorediate form of L. cactacea . However, chemistry clearly distinguishes the two species as P. oahuensis contains lichexanthone with stictic, cryptostictic and constictic acid ( Bungartz et al. 2015). Lecanora cactacea belongs to an unusual series of Galapagos lichens that commonly inhabit endemic cacti, either the pads of Opuntia species or the columnar trunks of Jasminocereus thouarsii (e.g. Opegrapha cactacearum , Parmotrema dominicanum , Lecanographa lyncea , Pyxine cocoë s, Pyrenula ochraceoflava , P. cerina , Roccella gracilis , etc.).

Additional specimens examined (paratypes). ECUADOR. GALÁPAGOS: Isabela, Volcán Sierra Negra, Volcán Chico on the northeastern slope of Sierra Negra, 0˚46’56.77’’ S, 91˚6’4.298’’W, 938 m alt., transition zone, young lava flow with very scattered vegetation ( Macraea laricifolia , Darwiniothamnus tenuifolia ), on SW-exposed trunk of Jasminocereus thouarsii , 14-Aug-2008, Bungartz, F. 8177 ( CDS 40823); 0˚46’57.80’’ S, 91˚5’59.40’’W, 944 m alt., transition zone, dry and rocky area (young lava), with cacti and Macraea laricifolia , slope 40° NE, on Jasminocereus thouarsii, Truong, C. 1174 ( CDS 39485).

Figures

FIGURE 13. Species in the L. subfusca-group; superficially similar species with pale to dark brown apothecial disc and melacarpella- or allophana-type exciple (coarse and fine or fine crystals only). A–B. Lecanora darwiniana (Bungartz, F. 4859, CDS 29055–holotype). A. Thallus rimose, with abundant, coarsely granular soredia all across its surface and along the apothecial margin, apothecial disc deep brown, epruinose. B. Apothecial section: exciple with both coarse and fine crystals (melacarpella-type), epihymenium lacking crystals, brownish pigment insoluble in K (glabrata-type), exciple breaking apart into granular soredia (in water, DIC). C–D. Lecanora cactacea (Bungartz, F. 8178, CDS 40824–holotype). C. Thallus areolate verrucose, growing on the flaky surface of cactus pads, apothecia large, distinctly sessile, margin soon conspicuously fissured, disc pale to deep brown, with age occasionally blackened. D. Apothecial section (in water, DIC): exciple evenly yellow brown throughout, filled with abundant, minute crystals that completely dissolve in KOH (allophana- type), epihymenium yellowish brown, not dissolving in KOH, lacking crystals (glabrata-type). E–F. Lecanora subcrenulata (Bungartz, F. 7617, CDS 38113). E. Thallus saxicolous, areolate, with large, distinctly sessile apothecia, margin moderately to strongly undulate with age, disc pale orange-brown, epruinose. G. Apothecial section (in water, DIC): exciple with both coarse and fine crystals (melacarpella- type), epihymenium with minute crystals and brown pigment (chlarotera-type). Scales: A, C, & E = 5 mm; B, D & F = 100 µm.