Lecanora darwiniana 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 : 42-43

Lecanora darwiniana Bungartz & Elix sp. nov. MycoBank no. 833372

Diagnosis. A species with small, distinctly sessile apothecia and an irregularly granular-blastidiate thallus, containing the xanthones thiophanic acid and 3- O -methylthiophanic acid.

Type:— ECUADOR. GALÁPAGOS: Santiago, along the trail from the caseta in La Central to La Bomba (at the coast), cerro ca. 1 km NE of the caseta and on the W-side of the trail, 0˚14’10’’ S, 90˚44’41’’W, 664 m alt., transition zone, vertical, SE-exposed cliff face with ferns ( Blechnum polypodioides and Pityrogramma calomelanos var. calomelanos ) growing in crevices, on SE-exposed front of cliff of conglomerated basalt tuff, 25-Mar-2006, Bungartz, F. 4859 ( CDS 29055– holotype).

( Fig. 13A–B )

Thallus saxicolous, thin, rimose-areolate to verruculose areolate, areoles closely adjoining but not interlocked; surface pale white to ivory, roughened, matt, epruinose, in large parts forming blastidiate, pseudocorticate granules which irregularly disintegrate into large patches of ecorticate, often confluent soredia; prothallus weakly developed, powdery arachnoid to compact, indistinct. Apothecia numerous, scattered, circular to slightly irregular in outline, 0.1–0.5 mm in diam., adnate to soon sessile, distinctly lecanorine, margin persistent, smooth to soon strongly granular-verruculose, granules irregularly forming soredia, disc plane to ±convex, deep mahogany brown, epruinose; hymenium hyaline, not inspersed; epihymenium lacking crystals, with a diffuse reddish brown pigment (arnoldiana -brown: K+ dull brown, HCl+ reddish brown, N−), pigment ±persistent, although fading in K (glabrata - type); proper exciple thin, indistinct, with few crystals; thalline exciple thick, irregularly disintegrating, with abundant small crystals obscuring few larger ones, only the small crystals soluble in K, the larger ones persistent (melacarpella - type); subhymenium and hypothecium hyaline; ascospores 8/ascus, simple, ellipsoid, (10.8–)11.3–14.6(–16.7) × (4.9–)5.8–7.6(–8.8) µm (n = 30). Pycnidia immersed, ostiole brown, wall hyaline; conidia short filiform, curved, 16–20 × ca. 1.9–1.5 µm (n = 10).

Chemistry: Thallus cortex P+ yellow, K+ orange, KC+ orange, C+ orange, UV+ dull orange; with atranorin [major], zeorin [major], unknown terpenes [minor], 3- O -methylthiophanic acid [minor], thiophanic acid [major]; [specimens examined with TLC: Bungartz, F. 4852 ( CDS 29048 ), 4859 ( CDS 29055 – holotype); Aptroot, A. 65570 ( CDS 32158 )] .

Etymology: Named in honor of Charles Darwin and the Charles Darwin Foundation.

Ecology and Distribution: Known only from the Galapagos; a few collections from semi-shaded basalt tuff.

Notes. The saxicolous L. darwiniana , is so far known only from the Galapagos. It is sorediate and has a chemistry similar to L. leproplaca Zahlbr. , a corticolous species reported by Guderley (1999) from Suriname and the Caribbean ( Dominica). In both species the soredia are fairly coarse and often confluent, but in L. darwiniana they are formed from coarse blastidiate granules that, like verrucae, cover the entire thallus and secondarily break apart into finer soredia. This contrasts with L. leproplaca , where granular soralia initially develop within distinctly delimited soralia, which later may merge. Both species have different apothecia. Guderley (1999) referred to L. leproplaca as the sorediate counterpart (p. 210: “ sorediöse Parallelsippe ”) of L. tropica . The size and anatomy of apothecia in both taxa is virtually identical. Both species have an epihymenium that belongs to the glabrata - type (lacking crystals, with a diffuse reddish brown pigment not dissolving in K) and a pulicaris - type exciple. Apothecia of L. darwiniana are generally smaller (less than 0.5 mm in diam.) than those of L. leproplaca / L. tropica (typically larger than 0.5 mm in diam.). The thalline exciple of all species contains large crystals, but in L. leproplaca / L. tropica these crystals are easily observed even without polarized light. They are rarely inspersed but never obscured by smaller crystals. Guderley (1999) calls this exciple pulicaris - type. The exciple of L. darwiniana instead belongs to the melacarpella - type. Although it also contains few large crystals, these crystals are almost entirely obscured by abundant much smaller ones. And the larger crystals are difficult to see unless the smaller ones are dissolved in K. If L. leproplaca is considered the sorediate counterpart of L. tropica , L. darwiniana resembles more closely the endemic L. schindleri ; both have the same exciple type. However, the two species nevertheless differ in their substrate (saxicolous vs. corticolous), they have a different epihymenium (glabrata - vs. pulicaris - type) and the apothecia in L. darwiniana are consistently much smaller than those of L. schindleri . We therefore describe L. darwiniana here as a new species.

Additional specimen examined (paratype). ECUADOR. GALÁPAGOS: Santiago, along the trail from the caseta in La Central to La Bomba (at the coast), cerro ca. 1 km NE of the caseta and on the W-side of the trail, 0˚14’10’’ S, 90˚44’41’’W, 664 m alt., transition zone, vertical, SE-exposed cliff face with ferns ( Blechnum polypodioides and Pityrogramma calomelanos var. calomelanos ) growing in crevices, on rock, 25-Mar-2006, Bungartz, F. 4852 ( CDS 29048); Coscojo abierto, 0˚13’12’’ S, 90˚45’45’’W, 725 m alt., transition zone, open woodland of Psidium galapageium , Zanthoxylum fagara , Bursera graveolens , Trema micrantha and shrubs of Clerodendrum molle in between, lava, on rock, 24-Mar-2006, Aptroot, A. 65570 ( CDS 32158).

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.