Sochting U, Lorentsen LB, Arup U. 2008. The lichen genus Caloplaca (Ascomycota, Lecanoromycetes) on Svalbard. Notes and additions. Nova Hedwigia 87(1-2): 69-96.
Thallus endosubstratic, staining the substrate whitish grey, irregular in outline, to 1 cm in diam. Apothecia moderately abundant to abundant, scattered or in loose groups, orbicular, 0.3-0.5 mm in diam., small, sessile, not to slightly constricted, lecanorine or biatorine; the disc is plane or eventually weakly convex, ferrugineous-red or -brown to dark brown, surface structure fine granulose, epruinose. Apothecial margin is initially prominent, eventually at disc level, thin (25 μm), becoming excluded, not or occasionally flexuose, ferrugineous-red to -brown, concolourous with disc, smooth and epruinose. Excipulum to 25-50 μm wide, with few or no algal cells; the inner, part is narrow and poorly developed, prosoplectenchymatous, strongly glutinized, towards the outer side brownish hyaline. Hypothecium hyaline, oil droplets present; the subhymenium is hyaline. Hymenium to 60 μm high, hyaline or with a diffuse colouration of reddish to brownish hyaline in the uppermost 10 μm; paraphyses ungelatinized or eventually gelatinized, ramifications present; terminal cells simple or swollen, 2-5.5 μm wide, hyaline or eventually conglutinated and coloured reddish brown; subterminal cells are 2-3 μm wide; epihymenium to 10 μm high, distinct, red to orange. Asci 50-55 × 15 μm. Ascospores c. 8 per ascus, ellipsoid, (10-)12-14.5 × 5-6(-8.5) μm; septum 4-5 μm.
SECONDARY METABOLITES: 7-chloroemodin, emodin, 7-Cl-citreorosein, 7-Cl-emodinal and 7-Cl-emodic acid; chemosyndrome C1. All orange or brown parts are K+ red and C+ red.
SUBSTRATE AND ECOLOGY: on wood, detritus and reindeer droppings. Habitat exposed to sun or partially shaded, dry.
NOTES: The species is similar to C. spitsbergensis, which grows on somewhat nutrient enriched lignum from drift wood. This particular environment may generate the mutually compressed, stronger developed apothecia of that species. Their chemosyndromes are identical, and the slight anatomical differences may be due to environmental modifications. In case further studies show them to be conspecific, the name C. caesiorufella will take priority.
C. caesiorufellais an arctic, subarctic and boreal species, found in North America, Greenland, Svalbard, Europe and Siberia (Søchting 1989, Søchting et al. 1992, Santesson et al. 2004, Søchting & Olech 1995, Elvebakk & Hertel 1996).