Flora of New Zealand Series

≡Verrucaria citrina Hoffm., Dtschl. Fl.: 198 (1796).

Description : Flora (1985: 65).

Chemistry : Soredia K+ violet-red; containing emodin, parietin, fallacinol, fallacinal, xanthorin and erythroglaucin (Santesson 1970: 2152).

N: South Auckland (Coromandel Peninsula, Te Aroha), Taranaki (Waitara). S: Canterbury (Weka Pass, E of Tekapo, Dashing Rocks, Timaru), Otago (Miller's Flat Cemetery, The Nuggets), Southland (Sharks Tooth near Forest Hill). Throughout, on concrete posts, paths and walls (it is an early coloniser of concrete paving stones often with Candelariella vitellina, Lecanora dispersa and Sarcogyne regularis), and on asbestos-cement cladding on walls and roofs, often forming extensive swards on these latter steeply sloping to vertical substrata; also on limestone and basic sandstone outcrops, occasionally on old leather (abandoned on dry inland soils), clay banks and on seashore rocks. In the Northern Hemisphere it is common on exposed calcareous and non-calcareous rocks (both coastal and inland), on concrete, soil, decorticated wood, lignum, dust-impregnated bark and occasionally over bryophytes. It seems likely that C. citrina as currently circumscribed comprises several distinct species and taxa of lower ranks (Arup 1993: 598), and a recent paper confirms this with Nordic collections being shown to be separable into at least five species (Arup 2006). A table showing distinguishing features of C. citrina and two closely related taxa, C. phlogina (Ach.) Flagey and C. flavocitrina (Nyl.) H.Olivier, is given in Sérusiaux et al. (1999: 20), and Kondratyuk et al. (2003: 635–637) give a key to species of the C. citrina group with mainly squamulose thalli, and also present a table of character states of C. citrina and allied taxa. It is a widespread species in the Northern Hemisphere from the Arctic to the Mediterranean and North Africa, Israel, Ukraine, India, Asia, North America and Hawai'i (Galun 1970; Nordin 1972; Hansen et al. 1987a; Søchting 1989; Awasthi 1991; Laundon 1992; Tønsberg 1992b; Arup 1993; Nimis 1993; Poelt & Hinteregger 1993; Santesson 1993; Esslinger & Egan 1995; Søchting & Olech 1995; Egea 1996; Elvebakk & Hertel 1996; Galun & Mukhtar 1996; Kondratyuk et al. 1996a, 1996b, 1998; Elix & McCarthy 1998; Boqueras 2000; Diederich & Sérusiaux 2000; Scholz 2000; Brodo et al. 2001; Fletcher & Coppins 2001c; Hafellner & Türk 2001; Llimona & Hladun 2001; Wetmore 2001; Nimis & Martellos 2003; Santesson et al. 2004). In the Southern Hemisphere it is known from Chile (Galloway & Quilhot 1999), Argentina (Calvelo & Liberatore 2001), Australia (McCarthy 2003c, 2006) and Antarctica (Filson 1974a; Øvstedal & Lewis Smith 2001)

Cosmopolitan

Illustrations : Galløe (1936: 83, pls 100–101); Filson (1974a: 3, pl. 1A–C); Jahns (1980: 239. pl. 593); Søchting (1989: 249, fig. 13); Dobson (1992: 82; 2000: 91; 2005: 99); Arup (1993: 602, figs 8, 9); Boqueras (2000: 134, fig. 16E; 135, fig. 17F); Wetmore (2001: 5, fig. 6); Brodo et al. (2001: 198, pl. 160); Arup (2006: 10, fig. 3A, B; 14, fig. 6B).

Caloplaca citrina is characterised by: the saxicolous habit; its orange to yellow-orange colour; its completely sorediate or unlobed, flat areolae with marginal soralia; and its restriction to exposed habitats.