Verrucaria hunsrueckensis Thüs, Killmann, Leh & Eb.Fisch., 2018

Thüs, Holger, Killmann, Dorothee, Leh, Burkhard & Fischer, Eberhard, 2018, Verrucaria hunsrueckensis (Verrucariaceae, lichenized Ascomycota), a new rare species with exceptionally slender ascospores from Germany, Phytotaxa 345 (1), pp. 26-34 : 29-30

Verrucaria hunsrueckensis Thüs, Killmann, Leh & Eb.Fisch. sp. nov. Fig. 2 A–D .

Mycobank no: MB823512

TYPE: — GERMANY. Rhineland-Palatinate, Hunsrück Hochwald National Park, Naturwaldreservat (Nature forest reserve) Ruppelstein, 49°41’58.39’’N 7°3’34.28’’S, alt. 742 m, 02.Oct. 2015, E.Fischer, B.Leh & D.Killmann 651/2015 (holotype BM [ BM 001089084]!, isotypes: B!, MNHM!, STU [SMNS-STU-F-0000063]!), GenBank accession numbers: MG 242446 ( ITS), MG 242451 (mtSSU).

Diagnosis. Verrucaria hunsrueckensis differs from other species in the genus by its ITS sequence and a combination of morphological characters: spores with an exceptionally large length/width ratio (on average>3.0), a goniocyst-like thallus structure, exciple with small diameter (90–150 μm) and dark coloured base, and the presence of a distinct involucrellum which reaches the bottom of the thallus and is more or less spreading laterally.

Thallus epilithic, granular at first, with slightly flattened goniocyst-like elements of 30–50 × 15–25 μm, surrounded by thin non-fimbriate brown prothallus, eventually granules merging into a thicker, up to 80 μm high, greenish- brown, later mostly brown crust with more or less granular to eventually almost smooth surface. In these late developmental stages the margins of goniocyst units within the thallus remain sometimes visible from above as dark lines, giving the thallus a mottled appearance under high magnification. Uppermost parts of thallus with a thin but distinctive brownish pigment layer (<1 μm thick), but with cell size identical to lower layers and not forming a structurally differentiated cortex. Thick thalli continuous to irregularly cracked. Medullary layer not differentiated.

Perithecia sparse in young thalli (12–49 / cm 2), eventually moderately dense in large and thick (older) thalli (60–128 / cm 2), small, 170–240 μm in diameter, more or less hemispherical and projecting over the surrounding thallus to sessile, particularly in young thalli. Basis covered by thallus or mostly naked. Involucrellum always distinct, slightly spreading towards the base, up to 45 μm thick in upper half, variable in lower half, in some perithecia thinning out to 10–15 μm below, ± constant or slightly thickening in others (pigmented area between 25–40 μm thick), different forms sometimes in the same thallus, area between involucrellum and exciple brownish in fruiting bodies with little spreading involucrellum but transparent in specimens with stronger lateral development of the fruiting body. Exciple 90–150 μm in diameter, with brown colour from top to bottom. All pigments unchanged after application of 15 % potassium hydroxide solution. Periphyse lumen t0.7–0.9 μm, outer parts of cell walls soon gelatinising, total width of periphyses app. 2.1–2.2 μm, (15–) 34–38 μm long, Asci 42–50 × 12–16 μm. Ascospores 12.0–16.5–20.4 (SD=2.1) × 3.0–5.0–6.1 (SD=0.8) μm. Length/width ratio 2.5–3.3–4.7 (SD=0.5, n=79).

Additional specimens studied: — 02. Oct. 2015, E.Fischer, B.Leh & D.Killmann 652/2015 (SMNS-STU-F-0000064) [ STU], 02.Oct. 2015, E.Fischer, B.Leh & D.Killmann 654/2015 (SMNS-STU-F-0000065) [ STU], Jan. 2016, E.Fischer, B.Leh & D.Killmann 201/2016 (SMNS-STU-F-0000066) [ STU].

Habitat: — On acidic quartzitic stones (pH of the surface: 5.0–5.6) in a scree ( Fig. 3 ) in an old growth beech forest (Luzulo-Fagetum), 740–760 m a.s.l.

Etymology: —Named after the type locality in the Hunsrück-Hochwald National Park.

Figures

FIGURE 2. Verrucaria hunsrueckensis, A. Holotype specimen, E.Fischer et al. 651/2015 [BM], bar = 5 mm.B. Specimen E.Fischer et al. 201/2016 [STU], bar = 1 mm. C. Spores from the holotype, bar = 20 μm. D. Section of a perithecium from the holotype, bar = 50 μm.

FIGURE 3. Nature forest reserve (Naturwaldreservat) Ruppelstein, type locality of Verrucaria hunsrueckensis.