Verrucaria funckii (Sprengel) Zahlbruckner

Schiavo, Lo, 2015, Revision of the Verrucaria elaeomelaena species complex and morphologically similar freshwater lichens (Verrucariaceae, Ascomycota), Phytotaxa 197 (3), pp. 161-185 : 174-175

Verrucaria funckii (Sprengel) Zahlbruckner ( Figs. 5 A–E )

Catalogus Lichenum Universalis 1: 41 (1921). — Pyrenula funckii Sprengel., Cryptogamische Gewächse besonders des Fichtelgebirg’s 32: 5, nr. 650 (1826).

Type:— [ GERMANY, possibly Bavaria, Fichtelgebirge] Auf Steinen in klaren Gebirgs-Bächen. [Sprengel in litt.], (lectotype designated by Thüs 2002 FR!; isolectotypes M!, BM!, F!) .

Prothallus whitish or absent. In eroded thalli, the black basal layer can be exposed on the thallus margins and is easily mistaken for a black prothallus. Thallus thick, 58–250 μm, smooth, usually without cracks when fresh but herbarium specimens often developing wide cracks over time. Light to dark brown in exposed sites, greyish to bright green in shade forms. Distinctly subgelatinous with algal cells usually arranged in vertical columns and air filled spaces around hyphae not visible in anatomical sections. Photobiont cells 4.5–8.7 in diameter, identified as Heterococcus sp. by molecular markers ( Thüs et al. 2011). Cortex with yellowish-brown pigment in sun exposed sites, pigmentation weak or absent in shaded sites. Perithecia more or less immersed or forming low projections, only in shade forms more exposed, usually covered by a thallus mantle, rarely with the involucrellum exposed in its upper parts, 319 to>1000 μm wide, neighbouring involucrella often merging to form a continuous black basal layer, perithecia density very variable from (7) 11.4–27–42.7 (71) [24/8] in an area of 25 mm 2. Involucrellum 15–20 μm thick, Periphyses 17.5–20 μm, asci 46–78 × 16.7–20.6 μm, ascospores (16.2) 19.4– 21.9 –24.5 (28.3) × (6.4) 6.9– 8.2 –9.5 (12.5) μm, length/width ratio (2.0) 2.4– 2.7 –3.0 (3.7) [61/9]. Halonate perispore often visible in fresh collections.

Habitat and distribution: Among all freshwater Verrucariaceae this is one of the few species which are usually found in permanently submerged conditions and to which the term aquatic is rightly applied. Sub-aquatic populations exist, but usually occur either in the splash water zone of more turbid water courses or on deeply shaded stream banks. The species is restricted to siliceous substrata and often found in rather soft water. It is a typical element of springs and headwaters where it can dominate the benthic community ( Wirth 1972, Nascimbene et al. 2007). In the lower stretches of streams it is less frequent and apparently is absent from larger rivers. This lichen is only known from sites with low or moderate silting and absent where deposition of fouling organic matter occurs. It is widespread across the temperate areas of the Northern Hemisphere but threatened in parts of Central Europe due to silting, competition from algae in polluted streams and extended dry periods following water extraction ( Thüs 2002, 2006).

Figures

FIGURE 5. Anatomy and habitus of Verrucaria funckii. A. Thallus of isolectotype (BM). B. Thallus of specimen Thüs & Türk W1803 from sun-exposed locality (BM). C. Thallus of specimen Thüs W1047 from half-shaded locality. D. Thallus of specimen Thüs W1171 from deeply shaded locality. E. Cross-section of a perithecium of the isolectotype (BM). Scale bar:A–D = 5 mm; E = 50 μm.