Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: crustose, areolate, central areoles often becoming crowded and thus ±subsquamulose, thin to moderately thickened, ±continuous; prothallus: sometimes present as a black, ±fimbriate outline surface: pale ivory to ochraceous, often with a pinkish tinge, dull, epruinose, phenocorticate, esorediate medulla: white, lacking calcium oxalate (H2SO4-) Apothecia: lecideine; (0.2-)0.3-0.5(-0.8) mm in diam., soon sessile margin: black, thin to moderately thickened, usually persistent, rarely excluded with age disc: black, ±pruinose, plane, becoming ±convex proper exciple: dispersa-type, inner excipular hyphae distinct, not reduced, pigmented, prosoplectenchymatous (textura oblita), extending from the deep reddish brown hypothecium (leptoclinoides-brown, textura intricata), outer excipular hyphae short-celled, cells angular, distinctly swollen (textura angularis) and ±carbonized with various amounts of a brown pigment (cf. elachista-brown, HNO3-) epihymenium: brown, pigmentation continuous with the outer exciple, inspersed with crystals (HNO3-) hymenium: hyaline, not inspersed with oil droplets; paraphyses: simple to moderately branched, apically swollen, with a brown pigment cap (cf. elachista-brown) asci: clavate, Bacidiatype, 8-spored ascospores: soon brown, 1-septate, narrowly ellipsoid, not constricted, with obtuse ends, not curved, (8-)13.7-[16.5]-19.3(-19.5) x (4-)5-[5.6]-6.2(-6.5) µm (n=50); proper septum: narrow, not thickening during spore ontogeny (Buellia-type); ornamentation: very faintly microrugulate (barely visible in DIC) Pycnidia: rare, globose, unilocular; ontogeny similar to the Umbilicaria-type conidiogenous cells: mostly terminal, rarely also intercalary (cf. conidiophore-type V) conidia: elongate bacilliform, straight, 7-10.5 x 0.5-1 µm (n=30) Spot tests: K+ yellow-red (rapidly forming crystals), P+ yellow, C- fluorescence: UV-(pale) iodine reaction: medulla non-amyloid Secondary metabolites: atranorin, norstictic with ±connorstictic acid (J. A. Elix, HPLC). Substrate and ecology: on bark, rarely on wood World distribution: according to Marbach (2000) a tropic-subtropical species known from cacti and tree bark Sonoran distribution: scattered in Baja California Sur. Notes: In the Sonoran Region the species could only be mistaken for an unusual form of B. erubescens, which has smaller apothecia generally lacking pruina. In some herbarium specimens, pruina are not very conspicuous, but the epihymenium is, nevertheless, inspersed with crystals. Buellia intermedioides also differs from B. erubescens in spore size and ontogeny. Spores of B. erubescens are broader and initially form a distinctly thickened septum that becomes thin with maturity; spores of B. intermedioides are narrowly ellipsoid and have no distinct septal thickening. They do not belong to the Callispora-type and the placement of B. intermedioides into Baculifera by Marbach (2000) is therefore problematic. In the Sonoran region, B. erubescens and B. intermedioides differ significantly in their ecology and distribution. Throughout most of its range, Buellia erubescens is essentially a montane to subalpine species, only found inland at higher elevations. In contrast, B. intermedioides is known only from lowland habitats, currently known only from the coast of Baja California Sur. Buellia erubescens can further be distinguished from B. intermedioides by its considerably shorter conidia and, at least within the Sonoran Region, specimens do not contain as much norstictic acid as B. intermedioides. Thus, B. erubescens reacts K+ yellow slowly changing to orange, and P- or slowly changing to faintly yellow. In contrast, B. intermedioides reacts distinctly K+ yellow rapidly changing to red, and distinctly P+ yellow. High concentrations of norstictic acid in thalli of B. intermedioides may also be responsible for a faint reddish or pinkish tinge that the ochraceous thalli develop with storage; in contrast, thalli of B. erubescens fade to gray with storage. Marbach (2000) suggested that this pinkish tinge was more characteristic for B. tobleri. He must have noticed the coloration when he annotated two specimens from the Sonoran Region in UPS as B. cf. tobleri. The two specimens are indeed very similar to B. tobleri, but they have shorter conidia, lack a pale outer exciple and were collected at low elevations. The material in UPS therefore agrees much better with B. intermedioides than with B. tobleri. Therefore, Buellia tobleri cannot be confirmed for the Sonoran Region.