Placopsis aspicilioides
Holotype: New Zealand. South I., Southland, Piano Flat, banks of Waikaia River, on rocks close to river with other species of Placopsis, Aspicilia, Lobothallia radiosa and Porpidia platycarpoides, 230 m, 1.iii.2001, D.J. Galloway 5165 – CHR 533513. Isotype – OTA 057851.
Description : Thallus closely orbicular, to spreading in irregular patches, closely attached, 2–5(–8) cm diam., often forming confluent, large patches, margins neatly plicate, entire, notched or irregularly incised, flabellate, flat to subconvex, without a marginal prothallus. Lobes contiguous, sometimes imbricate, 1–2 mm wide, expanding to 3 mm at margins, parallel, radiating from centre to periphery, separated by narrow to deep and gaping cracks, 1–2 cm long, then becoming distinctly areolate centrally, areolae angular, (0.5–)1–3(–5) mm diam., separated by deep, gaping cracks, surface of areolae, minutely congested–cerebriform (reminiscent of surface of P. dusenii). Upper surface pale to dark olive-green, grass-green or grey-green to brownish grey, here and there suffused ochraceous or rusty when moist, pale grey-white to pinkish brown to ochraceous in parts when dry, distinctly maculate when moist (×10 lens), smooth to delicately and shallowly wrinkled, flat to shallowly convex, sometimes with minute, hair-like longitudinal or transverse cracking, with a regular, finely velvety to minutely crystalline surface pruina, sometimes glistening in parts (×10 lens) and often noticeably granular at margins, without isidia, pseudocyphellae or soredia. Medulla white. Photobiont green, chlorococcoid, cells rounded, 5–8.5 μm diam. Cephalodia submarginal (rarely developing at lobe margins) to central, scattered to crowded, orbicular, 1–2(–5) mm diam., immersed in thallus to spreading above thallus, hemispherical and smooth at first, becoming flattened, and delicately plicate-ridged around margins and hummocky-papillate centrally at maturity, breaking apart into widely separated "islands" and deeply cracked when over-mature, sometimes secondarily recolonised by thalline lobes, bluish purple and translucent when moist, pale-pinkish to yellow-brown to rust-brown when dry, sometimes with cyanobiont-free areas and appearing "piebald", epruinose; cyanobiont Scytonema, in chains, cells rounded, ovoid to bean-shaped, often laterally compressed, 8–11.5 μm diam. Surface of some cephalodia parasitised by a minute, black, punctiform lichenicolous fungus. Apothecia developing centrally in areolate parts, distinctly aspicilioid, subimmersed in thalline areolae, solitary to crowded, rounded to deformed and somewhat angular through mutual pressure, 0.5–1(–1.5) mm diam., disc shallowly concave, matt, epruinose, pale to dark red-brown when moist, brown-black to black when dry, fissuring with age. Thalline margin prominent, persistent, 0.1–0.3 mm thick, concolorous with thallus, minutely crenate–striate (×10 lens) becoming inflated-corrugate when moist, slightly impressed in thallus, to level with thallus surface or projecting very slightly above it and appearing truncate-conical in developing fruits. Proper margin very thin, visible as a pale, raised pinkish or brown-pink rim or halo around disc. Epithecium yellow-brown to olivaceous, slightly granular, 12.5–15 μm thick. Hymenium colourless, 250–300 μm tall; paraphyses slender. Hypothecium pale pinkish brown, densely interwoven, 100–150 μm thick. Asci narrowly cylindrical with a long, tapering foot, 250–300 × 12–15 μm, the ascospores occupying the upper half. Ascospores uniseriate in ascus, broadly ellipsoidal to ovoid, apices rounded, contents oily-granular, or vacuolate, hyaline to pale rosy pink, 20–25 × 10–12.5(–15) μm. Pycnidia common, scattered thickly in central, areolate parts, more widespread towards lobe apices, immersed, 200–450 μm wide and deep, ostiole minute, red-brown or blackish, punctate-depressed. Conidia filiform, curved, 20–34 × 0.5 μm
Chemistry : Thallus K−, C+ red, KC−, Pd−; containing gyrophoric acid.
S: Otago (Lake Onslow, Loganburn Reservoir), Southland (Mt Hodges Dusky Sound, Cascade Creek, Eglinton River, Waikaia River). St: (Mt Anglem). C: (Perseverance Harbour). On riverine rocks and on sloping rock faces in tussock grassland in creekbeds and watercourses where it is occasionally to periodically inundated during periods of strong water flow. It is found both in shaded and open sites exposed to full sun, and it will colonise both vertical and horizontal rock faces. In some habitats it co-dominates with Placopsis perrugosa, while in others it forms mosaics with several crustose lichens including Lobothallia radiosa, Porpidia platycarpoides and species of Aspicilia and Placopsis. Campbell I., specimens associate with Stereocaulon argus, Pannaria dichroa, Trapelia sp., Rimularia psephota, Placopsis perrugosa, P. cribellans and Steinera sorediata.
Endemic
Illustration : Galloway (2004a: 153, fig. 2).
Placopsis aspicilioides is characterised by: an orbicular to spreading, closely attached thallus with neatly pleated margins; distinctive parallel cracking separating lobes towards margins, becoming areolate centrally (rather like P. dusenii); patches of granular pruina at or near margins to a continous thin coating of white and sometimes glistening pruina over the entire thallus surface; distinct aspicilioid, immersed apothecia developed towards centre of thallus; hymenium, 250–300 μm tall; slender, cylindrical asci with a long tapering foot; broadly ellipsoidal ascospores, 20–25 × 10–12.5(–15) μm, occupying the upper half of the ascus.
