Lecanora achroa Nyl. (1876: 263) MycoBank

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 : 36-40

Lecanora achroa Nyl. (1876: 263) MycoBank no. 387537

Type:— MAURITIUS. RODRIGUEZ ISLAND: exact locality unknown, Sep–Dec 1874, Balfour, J.B. s.n. [H-Nyl 27475– lectotype, designated by Guderley (1999)] .

( Fig. 10A–B )

Thallus corticolous, thin to moderately thickened, areolate to granular areolate, developing initially from isolated areoles on a whitish arachnoid hypothallus, areoles becoming contiguous with age; surface white to pale gray or pale greenish gray, smooth to slightly dull and ±verruculose, matt, epruinose, lacking soredia; prothallus well developed, whitish arachnoid to blackened and occasionally forming a blackened line, especially where different thalli meet. Apothecia numerous, often densely aggregated, circular to slightly irregular in outline, 0.3–0.9 mm in diam., semi-immersed to adnate, or sessile, typically crowded, soon lecanorine, margin persistent, entire, weakly crenate to almost verrucose, epruinose, concolorous with the thallus, disc ±plane, yellowish orange to brownish orange, epruinose; hymenium hyaline, not inspersed, epihymenium with crystals, almost hyaline to pallid yellowish brown (elachista - brown: dissolving in K, HCl± dull greenish, N−), both pigment and crystals soluble in K (chlarotera - type); proper exciple thin, indistinct, with few crystals; thalline exciple thick, distinctly corticate, with a few small crystals soluble in K and conspicuous large crystals insoluble in K (pulicaris - type); hypothecium hyaline; ascospores 8/ascus, simple, narrowly to broadly ellipsoid, (6.9−)8.1−11.1(−11.9) × (5.0−)5.2−6.8(−6.9) µm (n = 20). Pycnidia not seen.

Chemistry: Thallus cortex including thalline margin K+ yellow, C–, KC–, PD+ orange yellow, UV– (dull); Galapagos specimens contain atranorin [major], ±usnic acid [major], ±2’- O -methylperlatolic acid [major], and zeorin [major or minor]; [all specimens cited were analyzed with TLC].

Ecology and distribution: Pantropical (North, Central and South America, Indian Ocean, Australia, South Pacific), new to Ecuador and the Galapagos; an infrequent corticolous species in the dry zone (but difficult to differentiate from L. leprosa and thus possibly more common than the few cited specimens might suggest).

Notes: Guderley (1999) apparently confused Galapagos records of Lecanora achroa and L. leprosa with the very similar L. helva , when he reported that the Galapagos endemic, L. schindleri , is often associated with L. helva ( Guderley 1999, p. 227) . His distribution maps, however, only show L. leprosa (fig. 9C p. 165) and no Galapagos specimens of L. achroa or L. helva are cited ( Guderley 1999, p. 176: specimens of L. achroa , and p. 207: L. helva ). All three species, L. achroa , L. helva and L. leprosa are morphologically and anatomically extremely similar, but differ in their chemistry. Lecanora leprosa is easily distinguished by the presence of gangaleoidin, but reports as to which secondary metabolites are most characteristic for L. achroa vs. L. helva are not in agreement. According to Guderley (1999) L. achroa is characterized by usnic acid, ±atranorin, chloroatranorin, ±zeorin and other terpenes. Lumbsch & Elix (2004) and Ryan et al. (2004) report that accessory 2’- O -methylperlatolic acid may also be present, but according to Guderley (1999) this compound only occurs in L. helva . For L. helva Guderley (1999) reports the occasional presence of arthothelin, but Lumbsch & Elix (2004) and Ryan et al. (2004) consider this to be the major secondary metabolite characteristic of L. helva . Arthothelin has not been found in any Galapagos specimen and the presence of usnic and 2’- O -methylperlatolic acid best agrees with the chemistry that Lumbsch & Elix (2004) and Ryan et al. (2004) report for L. achroa . We therefore consider previous reports of L. helva erroneous and instead here now report L. achroa .

Specimens examined. ECUADOR. GALÁPAGOS: Floreana, trail going to Post Office Bay off the dirt road between highlands and Puerto Velasco Ibarra, 1˚15’54.5’’ S, 90˚26’30.69’’W, 194 m alt., dry zone, dense Prosopis juliflora shrubland with Waltheria ovata , Gossypium darwinii , some Bursera trees and one single Pisonia floribunda tree, on top of Pisonia floribunda branch, 14-Jan-2011, Bungartz, F. 9604 ( CDS 46883); W of dirt road to water tank, off the main dirt road to the highlands, 1˚16’56.10’’ S, 90˚28’50.89’’W, 67 m alt., dry zone, dense Prosopis juliflora shrubland with some Castela galapageia and few trees of Bursera graveolens , on S-exposed trunk of Bursera graveolens , 12- Jan-2011, Bungartz, F. 9399 ( CDS 46686). Isabela, Volcán Alcedo, along the trail going up the E-slope, at the NWside of the trail, 0˚24’5’’ S, 91˚2’36’’W, 420 m alt., dry zone, open Bursera graveolens stand with an occasional Pisonia floribunda and Zanthoxylum fagara and shrubs of Macraea laricifolia and Waltheria ovata , on trunk of Bursera graveolens , 09-Mar-2006, Bungartz, F. 4337 ( CDS 28421); cinder cones along the trail going up the E-slope, 0˚23’40’’ S, 91˚1’18’’W, 190 m alt., dry zone, basalt outcrops, at the bottom scattered Bursera graveolens trees and shrubs of Castela galapageia , on trunk of Bursera graveolens , 10-Mar-2006, Bungartz, F. 4483 ( CDS 28569), 4483 ( CDS 28569). Santiago, en el parte sureste de la isla, 0˚17’54’’ S, 90˚35’13.5’’W, 162 m alt., zona seca, bosque de Bursera graveolens y pocos árboles de Scalesia atractyloides , sobre lava jovén, Bursera graveolens , altura al pecho, sobre corteza, 20-Jul-2006, Nugra, F. 111 ( CDS 32765).

Figures

FIGURE 10. Species in the L. subfusca-group; superficially similar species with pale apothecial disc and pulicaris-type exciple (large crystals only). A–B. Lecanora achroa (Nugra, F. 111, CDS 32765). A. Thick rimose-areolate, white thallus with lecanorine apothecia with pale brown discs, growing on smooth bark of Bursera. B. Apothecial section with chlarotera-type epihymenium and pulicaris-type exciple. C–D. Lecanora leprosa. C. White, dispersed thallus granules on whitish prothallus with lecanorine apothecia with pale yellowish green discs, on smooth bark of Bursera (Bungartz, F. 6319, CDS 34534). D. Apothecial section with chlarotera-type epihymenium and pulicaris-type exciple (Bungartz, F. 6039, CDS 33718). E–F. Lecanora sulfurescens. E. White thallus with lecanorine apothecia with pale brown discs, growing on rock (Bungartz, F. 4054, CDS 27984). F. Apothecial section with pulicaris-type epihymenium and pulicaris-type exciple (Bungartz, F. 6562, CDS 34780). Scales: A, C, & E = 5 mm; B, D & F = 100 µm.