Ionaspis lacustris
≡Lichen lacustris With., Arr. Brit. pl. ed. 3, 4: 21 (1796).
≡Hymenelia lacustris (With.) M.Choisy, Bull. Mens. Soc. linn. Lyon18: 145 (1949).
Description : Thallus 0.1–0.4 mm thick, smooth, ±even, continuous to cracked (noticeably around apothecia), pale whitish cream or greenish to deep rust-red, effuse or forming mosaics and then delimited by red-brown prothalline lines. Apothecia 0.15–0.4(–0.6) mm diam., often crowded, ± immersed, or with a slightly raised proper exciple, rounded to subirregular, pale-pink to bright-orange when wet, becoming pale-orange to red-brown on storage. Proper exciple ±colourless, the upper and outer parts pale-brown to red-brown. Epithecium pale-orange to dark red-brown, inspersed with minute granules, not dissolving in K. Hymenium 90–105 μm tall. Ascospores broadly ellipsoidal to ±globose, 13–20 × 6–11 μm. Pycnidia 50–80 μm diam., red-brown. Conidia 4.5–6.5 × 1 μm.
S: Otago (Mt Cargill); Southland (Crombie Stream Waitutu Forest). C: On hard, siliceous rocks in stream beds, often ±immersed or inundated; often forming an extensive zone of mosaics with aquatic species of Anisomeridium, Porina, Staurothele, Strigula and Verrucaria (Johnson & McCarthy 1997; McCarthy & Johnson 1998). Known also from Great Britain, Europe, Scandinavia, North and South America and Australia (Nimis 1993; Santesson 1993; Esslinger & Egan 1995; Aptroot 2002e; Coppins 2002b; McCarthy 2003c, 2006; Nimis & Martellos 2003; Santesson et al. 2004).
Cosmopolitan
Illustrations : Wirth (1987: 209; 1995b: 421); Foucard (1990: fig. 107); Dobson (1992: 155; 2000: 169; 2005: 198); Malcolm & Malcolm (2001: 105, 106) all as Hymenelia lacustris;. Brodo et al. (2001: 363, pl. 399); Lumbsch et al. (2001: 24).
Ionaspis lacustris is characterised by: the saxicolous habit; the subimmersed, mosaic-forming creamish white to rust-red thallus; the pinkish to orange, aspicilioid apothecia; and globose to broadly ellipsoidal ascospores, 13–20 × 6–11 μm.
