Verrucaria subtilis Muell . Arg., Flora 57: 536, 1874

Pykaelae, Juha, Kantelinen, Annina & Myllys, Leena, 2020, Taxonomy of Verrucaria species characterised by large spores, perithecia leaving pits in the rock and a pale thin thallus in Finland, MycoKeys 72, pp. 43-92 : 43

Verrucaria subtilis Muell. Arg., Flora 57: 536, 1874

= Verrucaria hypophaea (J. Steiner & Zahlbr.) Servít, Stud. Bot. Cechoslov. 11(3): 114, 1950

Verrucaria rupestris var. hypophaea J. Steiner & Zahlbr., Ann. K. K. naturh. Hofmus. Wien 22: 107, 1908.Basionym. Type. [Croatia] Hungaria; ad saxa dolomitica prope pagum Pulac supra Fiume, ca. 250 m a.s.m, leg. J. Schuler, Kryptogamie exsiccatae 1521 (M-0164001!, PRM-789449!, syntypes).

=? Verrucaria infidula Zschacke, Rabenh. Krypt.-Fl. 9(1)1: 135, 1933. Type. [Poland,] Eitner, Sammlung H. Zschacke 4708 (B-600194849!, syntype?) (see Pykälä 2016)

Type.

[Switzerland] Bagnes-Thal, nördl. vom Hotel Monvoisin gegen den Plaine an Dolomitfelsen 16.9.1873 (G-00295028!, syntype); … Monvoisin & Bonat Mepa in Bagnes-Thal 1874 (G-00260361!, syntype?).

Description.

Prothallus absent. Thallus white, grey or pale brown, endolithic, or thinly epilithic, continuous to rimose, up to 0.1 mm thick. Perithecia 0.15-0.34(-0.44) mm in diam., (1/2-)3/4(-1)-immersed, leaving shallow to deep pits in the rock, few perithecia occasionally not leaving pits, sometimes covered by a thin thalline layer except for the ostiolar region; 40-160 perithecia/cm2. Ostiole inconspicuous, tiny, pale or dark, plane or depressed, in two specimens, several ostioles slightly projecting, ca. 20-40(-70) mm wide. Involucrellum apical or covering half of the exciple, rarely in few perithecia exceeding half of the exciple, 30-70(-80) mm thick, appressed to the exciple to clearly diverging from the exciple. Exciple 0.16-0.33 mm in diam., wall pale or pale brown (rather rare), usually dark brown or black, 18-30 mm thick. Periphysoids ca. 20-40(-50) × (1-)1.5-2.5(-3) mm, branching. Asci 58-84 × 22-28 mm, 8-spored. Ascospores 0-septate, (19.8-)22.9-25.2-27.4(-30.7) × (8.3-)9.6-10.5-11.4(-12.8) mm (n = 400), perispore 1 mm thick.

Habitat and distribution.

The species grows on various calcareous rocks and in lime quarries. It occurs both in sun-exposed and shady habitats. It is amongst the most common species of Verrucaria on calcareous rocks of southern Finland. It may occur in the whole country, but the northernmost sequenced specimens are from the biogeographical province of Koillismaa. In Finland, V. subtilis is the most common species of Verrucaria belonging to the Thelidium group and having perithecia leaving pits in the rock.

Other specimens examined.

Finland. Varsinais-Suomi, Lohja, Paavola, N of Rautaniemi, stony SE-slope, young Pinus sylvestris -plantation, on calcareous stone, 50 m alt., 60°13'N, 23°54'E, 21 May 2005, J. Pykälä 26865 (H); Pohja, Kuovila, 150 m NW of Valkjärvi, small rather flat calcareous rock outcrop, 50 m alt., 60°08'N, 23°23'E, 9 October 2006, J. Pykälä 29589 (H); Karkkila, Haavisto, 200 m N of Saaressuo, on calcareous rock outcrop, 132 m alt., 60°31'N, 24°22'E, 24 May 2008, J. Pykälä 32606 (H); Suomusjärvi, Sallittu, Huuttavanmäki, S-slope, on calciferous boulder, 110 m alt., 60°18'N, 23°37'E, 28 June 2008, J. Pykälä 32749 (H); Salo (Kiikala), Saari, Kalkkimäki, abandoned lime quarry, on NW-facing wall, 105 m alt., 60°25'N, 23°40'E, 4 July 2009, J. Pykälä 34601 (H); Salo (Kisko), Haapaniemi, Multsilta, calcareous rock outcrop, on shady N-facing wall, 65 m alt., 60°13'N, 23°29'E, 17 July 2009, J. Pykälä 35093 (H); Kemiönsaari ( Västanfjärd), Billböle, Svinberget, calcareous rock outcrop, on W-slope, st pc, 25 m alt., 60°03'N, 22°43'E, 4 Sept 2009, J. Pykälä 36819 (H); Länsi-Turunmaa (Parainen), Hyvilemp, Hyvilemp, abandoned lime quarry, on SW-facing wall, scarce, 15 m alt., 60°17'N, 22°12'E, 14 Sept 2009, J. Pykälä 37102 (H); Karjalohja, Pyöli, E of Innoonlampi, rocky forest, on calcareous boulder, 46 m alt., 60°13'N, 23°49'E, 28 Sept 2009, J. Pykälä 37329 (H), 37331 (H); Salo (Kisko), Haapaniemi, Sorronniemi, abandoned lime quarry, on SE-facing wall, scarce, 65 m alt., 60°13'N, 23°30'E, 4 June 2010, J. Pykälä 37794 (H);

Salo (Kisko), Jyly, 200 m NE of Purslammi, calcareous rock outcrop, on NW-facing wall, 68 m alt., 60°14'N, 23°36'E, 17 June 2010, J. Pykälä 38140 (H); Salo ( Särkisalo), Kaukosalo, Pyölinmäki, abandoned lime quarry, quarry spoil heap, NW-slope, on calcareous pebbles, 15 m alt., 60°07'N, 22°58'E, 17 June 2011, J. Pykälä 42225 (H); Koillismaa, Salla, Oulanka National Park, Pikkuköngäs, shore of river Oulankajoki, high cliff, dolomite rock outcrop, on SW-slope, 180 m alt., 66°25'N, 29°08'E, 13 Aug 2010, J. Pykälä 39870 (H); Kuusamo, Liikasenvaara, Iso Sirkkalampi 200 m E, SW-slope, young Larix -plantation, on dolomite boulder, rather scarce, 295 m alt., 66°21'N, 29°35'E, 18 Aug 2010, J. Pykälä 40280 (H); Salla, Oulanka National Park, Savilampi 850 m N, shore of Savinajoki river, river shore, on dolomite boulder, on S-facing wall, 182 m alt., 66°26'N, 29°10'E, 23 Aug 2011, J. Pykälä 44843 (H), 44844 (H); Keski-Pohjanmaa, Vimpeli, Vimpeli, Ryytimaa, lime quarry, quarry spoil heap, young deciduous forest, on calcareous boulders, rather scarce, 135 m alt., 63°09'N, 24°01'E, 31 Aug 2010, J. Pykälä 40596 (H);

Vimpeli, Vimpeli, Ryytimaa, lime quarry, S-slope, on pebbles, 125 m alt., 63°09'N, 24°01'E, 2 Sept 2010, J. Pykälä 40833 (H); Vimpeli, Möksy, Kotakangas, abandoned lime quarry, small quarry spoil heap, on pebbles, 122 m alt., 63°07'N, 23°58'E, 2 Sept 2010, J. Pykälä 40859 (H); Vimpeli, Möksy, Kotakangas, by abandoned lime quarry, quarry spoil heap, W-slope, on boulders, 120 m alt., 63°07'N, 23°58'E, 2 Sept 2010, J. Pykälä 40874 (H); Uusimaa, Vantaa, Sotunki, Bisa, 300 m E-NE, herb-rich forest, abandoned lime quarry, on SW-facing wall, 35 m alt., 60°17'N, 25°09'E, 7 June 2011, J. Pykälä 41857 (H); Pohjois-Karjala, Juuka, Nunnanlahti, Mustanvaara, dolomite rock outcrop, on SE-slope, 140 m alt., 63°09'N, 29°09'E, 14 July 2011, J. Pykälä 42540 (H); Etelä-Savo, Kerimäki, Ruokojärvi, Pitkäniemi, abandoned lime quarry, gravelly field, on calcareous pebbles, 85 m alt., 61°56'N, 29°00'E, 15 Sept 2011, J. Pykälä 45794 (H), 45817 (H), 45847 (H).

Notes.

Verrucaria subtilis may be confused with several other species treated in this paper (see descriptions of these species). Verrucaria cavernarum and V. difficilis may differ by often longer involucrellum and slightly larger spores. The species may also be mixed up with Verrucaria epilithea Vain. and Verrucaria muralis Ach. These species have shorter spores (17-26 mm long) and the perithecia are not leaving pits in the rock or the pits are shallow. The first specimens of V. subtilis from Finland were identified as Verrucaria mimicrans Servít and V. transfugiens Zschacke ( Pykälä and Breuss 2008). The type material of V. mimicrans has not been located and the identity of this species remains to be studied. Verrucaria transfugiens (see Pykälä 2016) differs in smaller spores and the presence of dark lines between contiguous conspecific thalli. Verrucaria hypophaea has usually been considered to belong to V. muralis or to V. schindleri Servít, which is said to differ from V. muralis by a dark exciple ( Breuss 2007). However, V. hypophaea clearly differs from V. muralis by larger spores and the perithecia commonly leaving deep pits in the rock. The characters of V. hypophaea fit well with V. subtilis .