Lecanora cerebriformis Bungartz & Aptroot, 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 : 23-26

Lecanora cerebriformis Bungartz & Aptroot sp. nov. MycoBank no. 833368

Diagnosis. A chalky, bright white, densely pruinose, continuous crust, that, when well developed, forms conspicuously cerebriform, saxicolous thalli, with large lecanorine apothecia, with a thick thalline margin and pallid, pruinose disc, lacking soredia; containing atranorin and protocetraric acid.

Type:— ECUADOR. GALÁPAGOS: San Cristóbal, Cerro Partido along trail from entrance to Cerro Pelado to El Ripioso, 0˚51’23’’ S, 89˚27’37’’W, 376 m alt., transition zone, rocky SW-exposed slope of hill with Jasminocereus thouarsii , Clerodendrum molle var. glabrescens , Psidium galapageium , Bromeliaceae and ferns growing in rock crevices, on rock, 28-Apr-2007, Bungartz, F. 6633 ( CDS 34853– holotype).

( Figs. 6C–G , 7A–D )

Thallus saxicolous, continuous, not distinctly fissured, uneven to ±verrucose (‘lumpy’), typically significantly thickened, soon distinctly convoluted, gnarled, soon becoming conspicuously cerebriform particularly in the center, i.e., with conspicuously inflated, swollen and convoluted protuberances, isolated or merging into a very thick crust; surface white, dull, densely whitish pruinose, lacking soredia; prothallus absent. Apothecia sparse to numerous, occasionally crowded and deformed by mutual pressure, circular or slightly undulate in outline, 0.5–1.5(–1.9) mm in diam., soon sessile and typically basally ±constricted, distinctly lecanorine with a markedly thickened, entire or barely crenate, whitish pruinose margin, concolorous with the thallus, disc concave to plane, pale beige to faintly carneous, densely whitish pruinose; hymenium hyaline, not inspersed, epihymenium with a diffuse, dull brown pigment (elachista -brown: dissolving in K, HCl± dull greenish, N−) and few to abundant minute crystals, mostly dissolving in K (residue of fine, rounded, reddish granules persistent, 0.5–1 µm); proper exciple thin, indistinct, with few minute crystals; thalline exciple very thick, of thin-walled, radiating hyphae with numerous, but inconspicuous photobiont cells obscured by abundant small crystals soluble in K, ecorticate or indistinctly corticate (outer cells more deeply brown); hypothecium hyaline; ascospores 8/ascus, simple, broadly ellipsoid to subglobose, (5.9–)8.1–10.3(–10.8) × (3.9–)4.7–6.3(–6.9) µm (n = 45). Pycnidia not seen.

Chemistry: Thallus cortex including apothecial margin P+ orange-red, C−, KC−, K+ yellow, UV− (pale yellow); with atranorin [major], protocetraric acid [major], ±lichesterinic acid [minor]; [specimens analyzed with TLC: Bungartz, F. 3654 ( CDS 27472 ), 5061 ( CDS 29274 ), 5215 ( CDS 29428 ), 6313 ( CDS 34525 ), 6633 ( CDS 34853 – holotype)] .

Etymology: Named for its unusual, brain-like growth form.

Ecology and distribution: Known only from the Galapagos, typically growing in the transition zone, occasionally also in the upper dry zone, on exposed to semi-sheltered, sunny to semi-shaded steep rock surfaces (large boulders, steep cliffs).

Notes: When well developed, L. cerebriformis has a conspicuous, unusual thallus morphology that may best be compared to inflated, puffed up “kernels of popcorn”. These strongly swollen, bullate, often irregularly ramified protuberances are often dispersed so that the substrate appears to be sprinkled with popcorn. Thalli can also merge into a thick, irregular crust with an extremely convoluted surface. The apothecia of the species have a thick margin, superficially similar in appearance to those of Ochrolechia , but with typical Lecanora - type asci.

This typical growth form of the species is termed ‘ cerebriform ’ since the thalli often appear to be folded, convoluted and swollen like the lobules of a brain, i.e., a cerebrum. The thalli can be surprisingly similar to those of Mobergia calculiformis , a species endemic to Baja California. Lecanora cerebriformis , however, has almost white, rarely very faintly pink (‘carneous’) apothecial discs and it has simple, hyaline spores. Apothecial discs of Mobergia are black to bluish black, and the species forms deeply olive brown, thick-walled ascospores characteristic of the Physciaceae .

Despite its name L. cerebriformis does not always form the distinctly cerebriform thalli; very rarely contiguous, indistinctly fissured thalli can be observed ( Fig. 6C ). Even these thalli, however, become thicker and ‘verrucose’ in the center and chemically and anatomically clearly belong to this species.

In the Galapagos a second species of Lecanora is also characterized by a cerebriform morphology but L. cerebrosorediata contains usnic acid rather than atranorin. It has rarely been found fertile (ascospores have not been observed) and is typically densely sorediate, the soredia brighter, more greenish than the otherwise pale yellowish green, pruinose surface. Despite their similarity, the species are probably not closely related and may represent ecological adaptations to the same habitat, as they often co-occur ( Fig. 7A ).

Additional specimens examined (paratypes). ECUADOR. GALÁPAGOS: Floreana, trail going to Post Office Bay off the dirt road between highlands and Puerto Velasco Ibarra, cliff at NE-side of trail (Mirador), 1˚17’4.298’’ S, 90˚26’36.60’’W, 365 m alt., transition zone, ca. 10 m high lava cliff within dense scrub of Clerodendrum molle , Croton scouleri and Macraea laricifolia , one single Acacia rorudiana on top of cliff, on rock, 25-Jan-2011, Bungartz, F. 10192 ( CDS 47611); Cerro Ventanas, top and upper slope at southern point of the ridge, 1˚16’25.89’’ S, 90˚25’42.20’’W, transition zone, lower transition zone; low vegetation of Lecocarpus pinnificatus and some Macraea laricifolia shrubs, on rock, 18-Jan-2011, Yánez-Ayabaca, A. 2035 ( CDS 48385); trail going to Post Office Bay off the dirt road between highlands and Puerto Velasco Ibarra, cliff at NE-side of trail (Mirador), 1˚17’4.298’’ S, 90˚26’36.60’’W, 365 m alt., transition zone, ca. 10 m high lava cliff within dense scrub of Clerodendrum molle , Croton scouleri and Macraea laricifolia , one single Acacia rorudiana on top of cliff, on rock, 25-Jan-2011, Yánez-Ayabaca, A. 2122 ( CDS 48492); along rim trail of Cerro Pajas, eastern part of rim, 1˚17’44.77’’ S, 90˚27’15.6’’W, 442 m alt., humid zone, low dense vegetation of Zanthoxylum fagara , Scalesia pedunculata , Macraea laricifolia , Croton scouleri and ferns ( Polypodium tridens ) over lava boulders; bryophytes hanging in curtains from trees, on rock, 26-Jan-2011, Bungartz, F. 10260 ( CDS 47679). Pinzón, along the trail going up from Playa Escondida, N- to W-facing cliff above a crater, 0˚36’29’’ S, 90˚40’14’’W, 318 m alt., transition zone, dry transition zone with Cordia lutea , Croton scouleri , and at the bottom of the cliff also Scalesia baurii ssp. baurii , on rock, 16-Feb-2006, Bungartz, F. 3654 ( CDS 27472); Aptroot, A. 64021 ( CDS 30582). San Cristóbal, rim of crater to the NW of Media Luna, inland from the NW-coast, 0˚43’51’’ S, 89˚18’55’’W, 149 m alt., transition zone, lower transition zone; basalt cliffs of inner and outer crater rim with scarce vegetation, on rock, 22-Apr-2007, Bungartz, F. 6313 ( CDS 34525); slope of Cerro Tortuga, ca. 4 km inland from the NW-coast, 0˚44’51’’ S, 89˚23’25’’W, 155 m alt., dry zone, rocky S-exposed slope with few Bursera graveolens , Piscidia carthagenensis , Zanthoxylum fagara , and Mentzelia aspera in the understory, on rock, 25- Apr-2007, Bungartz, F. 6568 ( CDS 34786); Cerro Partido along trail from entrance to Cerro Pelado to El Ripioso, 0˚51’23’’ S, 89˚27’37’’W, 376 m alt., transition zone, rocky SW-exposed slope of hill with Jasminocereus thouarsii , Clerodendrum molle var. glabrescens , Psidium galapageium , Bromeliaceae and ferns growing in rock crevices, on rock, 28-Apr-2007, Bungartz, F. 6650 ( CDS 34870); Cerro Colorado, enclosure for Calandrinia galapagosa near the viewpoint on the top, 0˚54’58’’ S, 89˚26’5’’W, 130 m alt., transition zone, open scrubland with Croton scouleri , Macraea laricifolia , Calandrinia galapagosa , Lecocarpus darwinii and few trees of Piscidia carthagenensis among lava boulders on SE-exposed slope of cinder cone, on rock, 29-Apr-2007, Bungartz, F. 6725 ( CDS 34969); sector of the “Gotera de agua”, cliffs of Cerro El Partido, 0˚51’25.60’’ S, 89˚27’34.89’’W, 377 m alt., transition zone, basalt rocks, on rock, 23-Aug-2008, Clerc, P. 08-332 ( CDS 40186); Cerro Mundo, at the top of the rock cliffs on the S side close to the summit, 0˚53’19.5’’ S, 89˚34’24.30’’W, 282 m alt., transition zone, with Bursera graveolens , Croton scouleri and Jasminocereus thouarsii , slope 15°, protected rock cracks on the cliff, on rock, 25-Aug-2008, Clerc, P. 08-398 ( CDS 40252). Santa Cruz, above the quarry Mina Granillo Rojo , off the main road to the channel, on the N side of the island, 0˚37’5.798’’ S, 90˚21’59.10’’W, 617 m alt., transition zone, open and dry forest of mainly Psidium galapageium , with some Scalesia pedunculata and Pisonia floribunda , and basalt outcrops, on rock, 21-Oct-2007, Bungartz, F. 7134 ( CDS 37619); Mina Granillo Rojo , on the N-side of the island, above the the mine, 0˚37’8.80’’ S, 90˚21’57.60’’W, 633 m alt., transition zone, lava outcrop in open forest of Scalesia pedunculata , Psidium galapageium and few Bursera graveolens , on rock, 21-Jan-2010, Bungartz, F. 8760 ( CDS 44641). Santiago, ca. 5 km inland from the E-coast, ± at the same latitude as Bahía Sullivan, 0˚16’37’’ S, 90˚37’24’’W, 163 m alt., dry zone, SE-exposed slope of lava boulders, on rock, 18-Jul-2006, Bungartz, F. 5215 ( CDS 29428); 0˚16’52’’ S, 90˚37’17’’W, 175 m alt., dry zone, rubble of older lava with very scarce vegetation of few Bursera graveolens trees, Macraea laricifolia , and Mentzelia aspera , on rock, 16-Jul-2006, Bungartz, F. 5061 ( CDS 29274).

‘ Lecanora pinguis- group’ (= Placodium sect. Endochloris sensu Ryan 1989 ; Figs. 8–9 )

The species of this group share distinctly areolate to placodioid, lobate or strongly convoluted (‘cerebriform’) thalli with a pale greenish yellow to deep yellow color due to the production of xanthones and rarely also usnic acid. Apothecia are lecanorine with a distinct thalline exciple typically containing large crystals.

Figures

FIGURE 6. Species in the L. pallida-group. A–B. Lecanora caesiorubella. A. Rimose-areolate thallus with fimbriate white prothallus (Bungartz, F. 4466, CDS 28552). B. Thick exciple of thin-walled radiating hyphae, evenly pale brown throughout, inspersed by minute crystals (Aptroot, A. 64592, CDS 31165). C–G. Morphological variation of Lecanora cerebriformis. C–D. Specimen with continuous to barely rimose, not distinctly cerebriform thallus (Bungartz, F. 10260, CDS 47679). C. Thallus flat, only where apothecia form in the center the thallus becomes barely convoluted. D. Thick exciple of thin-walled radiating hyphae, evenly pale brown throughout, inspersed by minute crystals. E–G. Strongly cerebriform specimens. E. Thallus (Bungartz, F. 5215, CDS 29428). F. Lecanora-type asci (Bungartz, F. 6633, CDS 34853–holotype; in Lugol’s iodine, DIC). G. Thick exciple of thin-walled radiating hyphae, evenly pale brown throughout, inspersed by minute crystals (Bungartz, F. 6633, CDS 34853–holotype). Scales: A, C & E = 5 mm; B, D & G = 100 µm; F = 10 µm.

FIGURE 7. Species in the L. pallida-group. A–D. Morphological variation of Lecanora cerebriformis. A. Mosaic of moderately convoluted, white thalli with apothecia of Lecanora cerebriformis and strongly convoluted sorediate thalli of L. cerebrosorediata with few apothecia (Bungartz, F. 8759, CDS 44640). B. Strongly convoluted, ‘cerebriform’ thallus (Bungartz, F. 5215, CDS 29428). C. Gnarled ‘cerebriform’ thallus (Bungartz, F. 5215, CDS 29428). D. Exuberantly coralloid ‘cerebriform’ thallus (Bungartz, F. 6633, CDS 34853– holotype). Scales: A, B, C & D = 5 mm.

FIGURE 8. Species in the L. pinguis-group. A–C. Lecanora atro-ocellata. A–B. Morphological variation A. General thallus aspect, pale yellow, discrete areoles, apothecia adnate to sessile, with thick, crenate margin and blackened, faintly pruinose disc (Bungartz, F. 7427, CDS 37914). B. Close-up of the thallus (Ertz, D. 11821, CDS 37180–holotype). C. Apothecial section (in water, DIC): exciple with large crystals, epihymenium aeruginose, in parts ±granular (Ertz, D. 11821, CDS 37180–holotype). D–G. Lecanora pseudopinguis. D–F. Morphological variation. D. Thallus flattened, rimose-areolate (Bungartz, F. 5194, CDS 29407). E. Thallus slightly convoluted (Bungartz, F. 7278, CDS 37762). F. Thallus gnarled, rimose-areolate, with fimbriate marginal areoles (Bungartz, F. 7772, CDS 38280). G. Apothecial section: exciple with pale brown cortex, packets of green photobionts inside, dispersed throughout with minute crystals (Bungartz, F.7278, CDS 37762). Scales: A, B, D & F = 5 mm; C & G = 100 µm; F = 10 µm.

FIGURE 9. Species in the L. pinguis-group. A–D. Morphological variation of Lecanora cerebrosorediata. A.Thallus flattened, continuous to barely rimose (Aptroot, A. 64123, CDS 30685). B. Mosaic of deep yellow rimose-areolate, fertile thalli of L. pseudopinguis mixed with cushions of convoluted, ‘cerebriform’, pale yellow, sorediate L. cerebrosorediata (Bungartz, F. 4800, CDS 28932). C. Thallus distinctly ‘cerebriform’ (Bungartz, F. 5212, CDS 29425). D. Thallus exuberantly coralloid ‘cerebriform’, with few apothecia (Bungartz, F. 6596, CDS 34816–holotype). Scales: A, B, C & D = 5 mm.