Thallus epilithic, crustose, to 24 mm in diam., irregular in outline, composed of scattered areoles, 0.4-0.5 mm thick; margin effigurate occasionally almost lobed, convex, well delimited; surface pale dusty yellow, often with a white epinecral layer, smooth with fine superficial fissures, matt; hypothallus absent; soralia are found peripherally on thallus normally developing from the underside of the margin, occasionally spreading inwards to laminal soralia, helmet-shaped, yellow, not or occasionally confluent; soredia 25-30 μm in diam., finely granular. Thallus cortex is 10-20 μm high, paraplectenchymatous, poorly differentiated. Algal layer scattered; medulla hyaline and loose. Apothecia in the type material were unripe, sparse to moderately abundant, scattered, laminal on thallus, orbicular, to 0.6 mm in diam., small, sessile to substipitate, not or slightly constricted, lecanorine; disc plane, yellow to pale orange, surface structure smooth, zeorine; apothecial margin initially prominent and distinct, eventually at disc level, thick, regular, concolourous with thallus surface, yellow, slightly brighter than disc, rough, sorediate; thalline exciple disolved in soredia, with many algal cells; proper exciple hyaline. Hypothecium and subhymenium hyaline. Hymenium 60 μm high, hyaline; paraphyses present, not gelatinized, ramifications scarce; terminal cells are swollen, 5-7 μm wide, hyaline; subterminal cells to 3 μm wide; epihymenium to 10 μm high, distinct, yellow to yellowish orange. Ascospores probably c. 8 per ascus, difficult to distinguish in the unripe material. Conidiomata pycnidial, moderately present to abundant, laminal on thallus, semiimmersed; conidia ellipsoid, 3.5-4 × 1.5-2 μm.
SECONDARY METABOLITES: emodin, fallacinal, parietin, parietinic acid, and teloschistin; chemosyndrome A. All yellow parts K+ red, C-.
SUBSTRATE AND ECOLOGY: on strongly eutrophicated chert and limestone, but occasionally also on detritus. Habitat exposed to sun or partially shaded, dry.
NOTES: C. elvebakkiana is recognized on a combination of morphological thallus characters. The scattered thallus areoles have a characteristic growth form starting as areoles with a surface composed of one or more domes. With time, the domes grow to become ± distinct tiny lobes or apothecia. The surface is evenly dusty yellow or with white necrotic areas, matt and often with fine superficial cracks. The reproductive strategy in C. elvebakkiana includes soralia, pycnidia and apothecia. The apothecia are rather frequent, but the examined apothecia were unripe. In a single section some very poorly developed spores were observed and the three best developed were measured to be 11 × 8 μm, 13 × 6 μm and 17 × 6 μm with only a weak indication of the bipolar structure.
Pycnidia are frequent, often more than one pr. areole, and easily recognized as ± immersed, orange spots on the surface of a dome or a lobe. Like in C. soropelta the soralia develop from the underside of the margin, but eventually the soralia in C. elvebakkiana spreads also to the more central parts of the thallus. Like in C. soropelta, but unlike C. tominii, the soredia are small, 25-30 μm.
Even though C. elvebakkiana is not a distinctly lobate species, it differs from C. soropelta’s smooth concave peltate, gregarious thallus by the softly folded-lobate areoles and the overall impression is a verruculose, convex and scattered thallus. It also resembles poorly developed specimens of C. decipiens but they are two well separated taxa based on the frequent and early developed apothecia in C. elvebakkiana and the development of soralia from the lobe margin and not centrally and laminal as in C. decipiens. The type of C. elvebakkiana grows on a highly eutrophicated chert-limestone conglomerate, together with C. saxicola and C. decipiens.
The new Caloplaca species is named Caloplaca elvebakkiana after the lichenologist Arve Elvebakk, Botanical Institute, University of Tromsø in Norway, whom we would like to honour for his inspiring work with the ecology and lichens of Svalbard, and for his instrumental assistance connected with the two first author’s research trips to Svalbard.