in Arup & al., Nord. J. Bot., 31: 45, 2013. Basionym: Caloplaca limonia Nimis & Poelt in Nimis & al. - Bull. Soc. linn. Provence, 45: 252, 1994.
Synonyms: Caloplaca citrina auct. ital. p.p.
Distribution: N - VG (Ravera & al. 2018), Ven (Vondrák 2008, Vondrák & al. 2009). C - Tosc (Nascimbene & al. 2021), Sar (Herb. Vondrák 10807). S - Pugl (Nimis & Tretiach 1999), Si (Nimis & al. 1994, 1996b, Vondrák & al. 2009).
Description: Thallus crustose, episubstratic, pale yellow to yellowish green, sometimes weakly whitish-pruinose, often >200 µm thick, forming a more or less continuous to areolate-granulose, up to 10 cm wide crust. Areoles flattened, contiguous, 0.2-2.5 mm wide, densely covered in diffuse, 40-80(-140) µm thick, laminal blastidia and true soralia produced from cracked blastidia, or after the blastidia have eroded. Upper cortex paraplectenchymatous, evident only in young squamules; medulla white, rather thick. Apothecia rather frequent, zeorine, at first immersed, then sessile and constricted at base, with a yellow to yellow-brown, concave to flat disc, a yellow proper margin, and a thick, yellow, sorediate-blastidiate, finally sometimes excluded thalline margin. Proper exciple of more or less radially to irregularly arranged, strongly swollen hyphae that neither give rise to a recognizable paraplectenchymatic structure, nor to a true cortex; epithecium yellowish, K+ red; hymenium colourless, c. 100 µm high; paraphyses loose, c. 1.5 µm thick, the last 2-3 cells larger, the apical cell c. 8 µm wide, more or less spherical, covered by an epipsamma; hypothecium colourless. Asci 8-spored, cylindrical-clavate, functionally unitunicate, apically thickened with a broad internal beak, the inner part of apex and external cap I+ blue, Teloschistes-type. Ascospores 2-celled, polarilocular, hyaline, ellipsoid to subglobose, 8-16 x 4-8 µm, the equatorial thickening (“septum”) 3-5.5 µm (c. 40 % of spore length). Photobiont chlorococcoid. Spot tests: thallus and apothecia K+ red, C-, KC- P-, UV+ pale orange. Chemistry: thallus and apothecia with parietin (major), fallacinal, emodin, teloschistin and parietinic acid (minor), corresponding with chemosyndrome A of Søchting (1997).
Note: on calcareous rocks or on base-rich, hard siliceous cliffs in dry and sun-exposed to shaded and damp situations, but also on twigs of maritime shrubs or on soil, below the montane belt. The species, described from the calcareous cliffs along the coast of the Island of Marettimo, is also known from inland localities, and is certainly more widespread in Italy; earlier records might be under F. citrina s.lat.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)