Notes on Lecanora subcavicola. The phenotypic species circumscription in the complex including Lecanora brandegeei, L. cavicola and L. subcavicola requires further examination because specimens display an impressive range of variation in morphology including the presence and absence of soredia as well as secondary chemistry. Lectotypification of L. subcavicola is therefore postponed until results from an ongoing study based on a broader selection of specimens by J. Hollinger and collaborators are available. According to our phylogenetic research Lecanora subcavicola (collected at its locus classicus) and L. cf. subcavicola (collected in the Sierra Nevada and Great Basin) are separate species. Neither species is closely related to Pulvinora, although they have similar apothecia with photobionts below the hypothecium. Specimens of Pulvinora, however, have a contiguous algal layer below the hypothecium hypothecium, whereas in L. subcavicola and L. cf. subcavicola the algal layer appears to be mostly marginal and interrupted in the center. Although, at first glance, the apothecia thus appear structurally similar, their ontogeny nevertheless is distinctly different: In Pulvinora, apothecia are distinctly mycolecanorine, i.e., the thalline exciple (amphithecium) is persistent, although devoid of algae (the algae forming a contiguous layer below the hypothecium, but not extending into the margin). In L. subcavicola only immature apothecia are distinctly lecanorine (with photobionts in their margin). As the apothecial discs become increasingly convex, this thalline margin is pushed aside and replaced by an expanding proper exciple (parathecium). Externally, the morphology of both ontogenies appears similar: as the convex disc pushes the margin aside, the mature apothecia appear increasingly ‘‘emarginate.’’ Internally, however, the ontogenetic transition is different. In Pulvinora the proper exciple remains reduced, and the margin, although increasingly pushed below and devoid of algae, nevertheless remains composed of thalline hyphae, and is contiguous with the cortex of the surrounding thallus. The species we have referred to here as Lecanora cf. subcavicola is very similar morphologically to L. subcavicola in both thallus structure and apothecial anatomy. Both species grow in similar sheltered habitats in the alpine, and indeed were found growing together near the type locality, although their populations barely overlap, with L. subcavicola preferring more sheltered sites on the northern slope of Mount Agassiz. The primary difference is the secondary chemistry: L. cf. subcavicola contains atranorin, psoromic acid and zeorin. Also, L. subcavicola typically has darker, greener areoles which turn orange in the herbarium and a well developed hypothallus. Lecanora cf. subcavicola has persistently white or occasionally brownish areoles, rarely with a well-developed hypothallus. Furthermore, L. cf. subcavicola is a juvenile parasite, primarily on Rhizoplacanovomexicana (H.Magn.) Leavitt et al., Lecanora sierrae B.D.Ryan & T.H.Nash and Pleopsidium flavum (Bellardi) Körber. It is interesting to note that this secondary chemistry is also present in Lecanora formosa (Knoph & Leuckert 2000), which differs from L. cf. subcavicola in having an autonomous, cracked-areolate, determinate thallus and interrupted algal layer. Description of L. cf. subcavicola awaits further study in order to clarify its relationships with L. cavicola, L. subcavicola and L. formosa.
Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: crustose, bullate-areolate, to c. 3 cm across, up to 1-2 mm thick centrally, thinner towards periphery; prothallus: white, distinctly fibrous and +radiating, visible at periphery of thallus areoles: +contiguous but mostly discrete, becoming constricted at the base and somewhat lifted off the substrate, but not stipitate, 0.3-1 mm across, convex to occasionally somewhat foveolate or cerebriform, rounded to crenate-lobed and irregular upper surface: dark orange-yellow (to medium orange or brownish orange), turning moderate yellow to light orange-yellow or light olive brown when wet, dull to rather weakly shiny, epruinose, esorediate upper cortex: pale brown, with +unoriented, gelatinized hyphae, c. 25 um thick, often with dead algal cells, interspersed with fine granules soluble in K but insoluble in N; epinecral layer: 15-25 µm thick medulla: loose, cottony, without granular deposits, with 3-4 µm wide hyphae; algal layer: +continuous, c. 100 µm thick; algae: 10-15 µm in diam. lower cortex: present on uplifted parts, similar to and continuous with upper one lower surface: slightly paler than upper, without rhizinal strands Apothecia: lecanorine but often appearing biatorine or lecideoid, numerous, becoming crowded in places, borne laminally to marginally, 1-3 per areole, adnate to sessile, becoming constricted at base, 0.5-1(-2) mm in diam. disc: brownish black, paler and dark-spotted when wet, dull, initially concave but then plane to distinctly convex, finely and lightly white-pruinose margin: concolorous with thallus or becoming dark brown or blackening, 0.1-0.2 mm wide, entire to flexuous or coarsely crenate, raised and persistent for a while or soon becoming excluded, without a parathecial ring amphithecium: present, with an algal layer in center of margin and extending below the hypothecium where it forms an uneven to interrupted layer, with a poorly differentiated medulla without granules or crystals, corticate; cortex: inner part hyaline or pale and with unoriented hyphae c. 3 µm wide and 10 µm long; outer 10-25 µm either pale and inspersed with granules as in thallus cortex or becoming brownish black with radiating hyphae with somewhat enlarged brown-black apical cells, overall 50-75 µm thick, with an epinecral layer 1015 µm thick parathecium: hyaline, poorly differentiated epihymenium: brown-black, K-, N+ red, inspersed with fine granules insoluble in K and N, with thin covering of coarser granules, c. 10 µm thick hymenium: hyaline, 4555 µm tall; paraphyses: simple to forked; +coherent, often clustered together near the tips into groups of 3-5; cells: c. 10 x 1-1.5 µm, the top 1-3 cells shorter and enlarged to 3-4 µm wide, with brown-black to olive-black walls; subhymenium: pale yellow-gray to pale brown, c. 25 µm thick, sometimes with oil droplets; hypothecium: hyaline to pale yellow, 75-100 µm thick centrally, with conglutinate, unoriented hyphae with cells 5-7 µm across and narrow lumina asci: clavate, 35 x 11-17 µm, 8-spored ascospores: hyaline, simple, mostly broadly ellipsoid, (5-)7-10(-12) x 4-6(-7.5) µm, somewhat thick-walled Pycnidia: common in places, immersed, c. 150 µm deep, 100 µm wide; wall: pale brown but dark brown to black around the ostiole; conidiogenous cells: simple to forked; cells: c. 10 x 2-3 µm conidia: formed acrogenously, filiform, straight to curved, 12-15 x 1 µm Spot tests: cortex K+ yellow (appearing more strongly orange-yellow), C-, KC- P-; medulla K-, C-, KC- P+ strongly yellow Secondary metabolites: cortex with atranorin; medulla with alectorialic acid (major) and unknowns. Substrate and ecology: on volcanic rock, with a yellow Acarospora, Lecanora bicincta, and Umbilicaria virginis Sonoran distribution: Arizona, known only from the type locality. Notes: Lecanora subcavicola closely resembles L. cavicola in the apothecia and in the form and color of the thallus, but lacks soralia. Other differences are that in L. subcavicola the medulla does not become lacunose or hollow, and the hyphae are not encrusted with crystals; the apothecial cortex is evenly thickened rather than expanded below, the parathecium is scarcely differentiated, the epihymenium is interspersed with fine granules, the paraphyses lacking oil droplets, and the conidia are somewhat shorter. Lecanora subcavicola is similar to L. pringlei subsp. brandegei but differs in: 1) its thallus being thinner, more crustose (verrucose-areolate), with a whitish prothallus; 2) its surface, mostly dull, pale orange, without olive or black tinges; 3) its upper cortex, thinner; 4) its apothecia pruinose, usually soon convex and immarginate; 5) its proper parathecium, poorly differentiated, not evident from above; 6) its epihymenium having granules, K-; 7) its paraphyses not being constricted at the septa, clustered; and 8) its pycnidial ostiole being black. On some thalli or parts of thalli the apothecia are mostly scattered and concave with distinct thalline margins, on others they are mostly crowded, convex and immarginate.