Taxonomy of Verrucaria species characterised by large spores, perithecia leaving pits in the rock and a pale thin thallus in Finland Author Pykaelae, Juha Biodiversity Centre, Finnish Environment Institute, Latokartanonkaari 11, 00790 Helsinki, Finland https://orcid.org/0000-0002-7566-9310 juha.pykala@ymparisto.fi Author Kantelinen, Annina Botanical Museum, Finnish Museum of Natural History, P. O. Box 7, FI- 00014 University of Helsinki, Finland Author Myllys, Leena Botanical Museum, Finnish Museum of Natural History, P. O. Box 7, FI- 00014 University of Helsinki, Finland https://orcid.org/0000-0002-9566-9473 text MycoKeys 2020 72 43 92 http://dx.doi.org/10.3897/mycokeys.72.56223 journal article http://dx.doi.org/10.3897/mycokeys.72.56223 1314-4049-72-43 5243D130A7EF55F3856E1E3722F204D5 Verrucaria bifurcata Pykaelae , Kantelinen & Myllys sp. nov. Fig. 2A Diagnosis. Species characterised by pale, usually endolithic thallus, perithecia leaving shallow to deep pits in the rock, very variable involucrellum appressed to the exciple and ascospores (21-)24-28(-30) x (9-)10-12(-13) mm, morphologically rather similar to the other Finnish species of the V. subtilis complex, but the ITS sequence divergence between the species is 1.7-3.9%. Holotype. Finland. Varsinais-Suomi, Laensi-Turunmaa (Parainen), Ersby, 150 m SE of Stormossen, abandoned lime quarry, quarry waste hill, S-slope, on pebbles, 27 m alt., 60°17'N , 22°15'E , 3 Sept 2009 J. Pykaelae 36722 (H9205739, GenBank accession number: MT229720). Description. Prothallus absent. Thallus white, grey or pale greyish-brown, endolithic or thinly epilithic, continuous or small patches surrounding perithecia, ca. 20-60 mm thick, algal cells (4-)5-8 mm. Perithecia 0.13-0.26 mm in diam., (1/2-)3/4(-1)-immersed, leaving shallow to deep pits in the rock, sometimes thinly thalline covered; 80-140 perithecia/cm2. Ostiole inconspicuous, tiny, pale or dark, plane or depressed, ca. 20-30 mm wide. Involucrellum absent, apical, to the exciple base level or enveloping the exciple, 20-60 mm thick, appressed to the exciple. Exciple 0.18-0.27 mm in diam., wall dark brown or black, ca. 20-30 mm thick. Periphysoids ca. 25-35 x 1.5-2.5 mm. Asci 60-104 x 22-33 mm, 8-spored. Ascospores 0-septate, (20.6-)23.8-25.8-27.8(-30.3) x (8.7-)10.0-11.0-12.0(-12.9) mm (n = 117), perispore 1-1.5 mm thick. Habitat and distribution. All finds are from lime quarries or road cuttings of calcareous rocks. The species seems to prefer pebbles and stones in lime quarries. It occurs both in sun-exposed and rather shady habitats. The specimens are from SW and SE Finland. This suggests that V. bifurcata has a southern distribution in Finland. Etylomogy. The epithet refers to the dualistic nature of the involucrellum of the species: absent or short vs. long or enveloping the exciple. Other specimens examined. Finland. Varsinais-Suomi, Saerkisalo , Foerby , E of Vaehaemaankaula , abandoned lime quarry, beneath NW-facing wall, on stone, 7 m alt., 60°05'N , 22°52'E , 23 July 2008, J. Pykaelae 33120 (H); Laensi-Turunmaa (Parainen), Simonby, Gropen, abandoned lime quarry, road cutting of calciferous rock, on pebbles, 15 m alt., 60°16'N , 22°13'E , 16 Sept 2009, J. Pykaelae 37228 (H); Etelae-Savo , Kerimaeki , Ruokojaervi , Pitkaeniemi , abandoned lime quarry, on NE-facing wall, 90 m alt., 61°56'N , 29°00'E , 15 Sept 2011, J. Pykaelae 45762 (H). Notes. Verrucaria bifurcata is a somewhat puzzling species as it has a very variable involucrellum. Two specimens are characterised by an absent or small involucrellum and two by a deep reaching involucrellum. In the former case, the involucrellum varies within a specimen from absent to apical. In the latter case, the involucrellum extends to the exciple base level or envelopes the exciple. Verrucaria bifurcata cannot be identified with certainty without ITS sequencing. Nevertheless, it shows morphological variation differing from the other species in the V. subtilis complex. Verrucaria bifurcata is the only species in the V. subtilis complex in which involucrellum may be absent or enveloping the exciple. In V. bifurcata , the involucrellum is always tightly appressed to the exciple and sometimes it is difficult to find out whether the involucrellum is absent or enveloping the exciple. The specimen 45762 was originally identified as V. adelminienii Zschacke ( Pykaelae 2013 ). However, the type of V. adelminienii is not identifiable ( Pykaelae 2016 ). Furthermore, the spore size in the original description ( Zschacke 1933 ) is smaller than the spore size in the Finnish specimen.