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 kuusamoensis Pykaelae , Kantelinen & Myllys sp. nov. Fig. 2E Diagnosis. Species characterised by pale, usually thinly epilithic thallus, rather large perithecia leaving shallow to deep pits in the rock, involucrellum usually covering more than half of the exciple, ascospores (21-)26-30(-34) x (9-)11-13(-14) mm, morphologically difficult to separate from V. subdevergens , but the sequence divergence in ITS 6.8-7.4%. Type. Finland. Koillismaa, Kuusamo, Juuma, Oulanka National Park, Hautaniitynvuoma, gorge, dolomite rock outcrop, on high NE-facing wall, 190 m alt., 66°15'N , 29°26'E , 21 Aug 2011, J. Pykaelae 44703 (H9205113 - holotype, UPS - isotype, GenBank accession number: MT229776). Description. Prothallus absent. Thallus white, grey or more rarely pale brown, endolithic or usually thinly epilithic, continuous or rimose, often farinose, up to 0.2 mm thick, algal cells (4-)5-7 mm, contiguous conspecific thalli sometimes separated by a dark line, 0.12-0.35 mm wide, present in only few specimens. Perithecia 0.17-0.45 mm in diam., (1/4-)1/2-3/4(-1)-immersed, leaving shallow to deep pits in the rock, rarely few perithecia not leaving pits, often thinly thalline covered except apex; (30-)40-120 perithecia/cm2. Ostiole tiny, pale or dark, plane or depressed, ca. 20-40(-60) mm wide, occasionally wider ostiolar depression up to 110 mm wide. Involucrellum covering half of the exciple or to the exciple base level, rarely in few perithecia enveloping the exciple, (30-)40-70(-80) mm thick, appressed to the exciple or slightly or moderately diverging from it. Exciple 0.19-0.29 mm in diam., wall dark brown or black, rarely pale, ca. 20-42 mm thick. Periphysoids ca. (20-)25-40 x (1.5-)2-2.5(-3) mm. Asci 68-102 x 25-34 mm, 8-spored. Ascospores 0-septate, (21.4-)25.5-27.9-30.3(-34.5) x (9.3-)11.3-12.2-13.1(-14.2) mm (n = 312), perispore 1 mm thick. Habitat and distribution. Verrucaria kuusamoensis is rather common on dolomite rocks in the Oulanka area in the municipalities of Kuusamo and Salla in the biogeographical Province of Koillismaa (Ks). It seems not to occur in southern Finland. Etymology. Most specimens of the species originate from the Kuusamo area. Other specimens examined. Finland. Koillismaa, Kuusamo, Paljakka, E shore of Kuusinkijoki river, Kiukaankorva, dolomite rock outcrop, on overhanging NW-facing wall, scarce, 213 m alt., 66°11'N , 29°38'E , 5 Aug 2009, J. Pykaelae 35710 (H); Kuusamo, Oulanka National Park, Pikkukoenkaeaenkuru , herb-rich heath forest, small dolomite rock outcrop, on W-facing wall, 165 m alt., 66°21'N , 29°19'E , 6 Aug 2009, J. Pykaelae 35857 (H); Kuusamo, Oulanka National Park, Pikkukoenkaeaenkuru , dolomite rock outcrop, on SW-facing wall, 175 m alt., 66°21'N , 29°19'E , 8 Aug 2009, J. Pykaelae 35920 (H); Kuusamo, Oulanka National Park, Pikkukoengaes , N shore of river Oulankajoki, dolomite rock outcrop, on SW-facing wall, 160 m alt., 66°22'N , 29°19'E , 12 Aug 2009, J. Pykaelae 36254 (H); Kuusamo, Oulanka National Park, Kiutakoengaes , Pinus sylvestris -dominated forest, steep SE-slope, dolomite rock outcrop, on SE-facing wall, rather scarce, 175 m alt., 66°22'N , 29°19'E , 12 Aug 2009, J. Pykaelae 36294 (H); Salla, Oulanka National Park, 400 m N of Savilampi, shore of river Savinajoki, dolomite rock outcrop, on NE-slope, scarce, 178 m alt., 66°25'N , 29°10'E , 13 Aug 2009, J. Pykaelae 36335 (H); Kuusamo, Oulanka National Park, Kiutakoengaes 400 m N, Pinus sylvestris -dominated forest, small dolomite rock outcrop, on SW-slope, 165 m alt., 66°22'N , 29°19'E , 2 Aug 2010, J. Pykaelae 39052 (H); Kuusamo, Oulanka National Park, Kiutakoengaes , by the rapids, S shore of Oulankajoki river, calciferous (dolomite) schistose rock outcrop, NE-slope, on E-facing wall, rather scarce, 152 m alt., 66°22'N , 29°20'E , 13 Aug 2010, J. Pykaelae 39900 (H); Salla, Oulanka National Park, W of Savikoski, cliff, dolomite rock outcrop, on NW-facing wall, very scarce, 185 m alt., 66°25'N , 29°10'E , 17 Aug 2010, J. Pykaelae 40219 (H); Kuusamo, Oulanka National Park, Taivalkoengaes , shore of Oulankajoki river, Picea abies -dominated herb-rich forest, dolomite rock outcrop, on NE-facing wall, 175 m alt., 66°24'N , 29°11'E , 20 Aug 2011, J. Pykaelae 44563 (H); Kuusamo, Oulanka National Park, Taivalkoengaes , shore of Oulankajoki river, Picea abies -dominated herb-rich forest, dolomite rock outcrop, on E-facing wall, 175 m alt., 66°24'N , 29°11'E , 20 Aug 2011, J. Pykaelae 44570 (H); Kuusamo, Juuma, Oulanka National Park, Hautaniitynvuoma, gorge, dolomite rock outcrop, on high NE-facing wall, 190 m alt., 66°15'N , 29°26'E , 21 Aug 2011, J. Pykaelae 44694 (H), 44696 (H); Kuusamo, Juuma, Oulanka National Park, Hautaniitynvuoma, gorge, stony NW-slope with sparse stunted birches, close to bottom, on dolomite stone, 182 m alt., 66°15'N , 29°26'E , 21 Aug 2011, J. Pykaelae 44744 (H); Salla, Hautajaervi , Kurtinniittykuru, cliff, dolomite rock outcrop, on SE-facing wall, scarce, 195 m alt., 66°26'N , 29°09'E , 24 Aug 2011, J. Pykaelae 44980 (H); Kuusamo, Oulanka National Park, Halosenkuru gorge, NW-slope, Picea abies -dominated forest, dolomite rock outcrop, on NW-facing wall, 215 m alt., 66°21'N , 29°26'E , 27 Aug 2011, J. Pykaelae 45231 (H); Kuusamo, Oulanka National Park, Halosenkuru, gorge, dolomite rock outcrop, on SE-facing wall, scarce, 235 m alt., 66°21'N , 29°26'E , 28 Aug 2011, J. Pykaelae 45330 (H). Notes. The exciple wall of V. kuusamoensis is usually dark brown or black. However, one specimen with a pale exciple wall and one specimen with both pale and dark exciple walls have similar ITS sequences compared to the specimens with dark exciple walls. This species was erroneously reported as V. subjunctiva by Pykaelae (2010a) , while V. subjunctiva has larger spores and longer periphysoids. Verrucaria devergens has a shorter involucrellum. Verrucaria kuusamoensis may be most difficult to separate from V. subdevergens and V. difficilis . These species show wide overlap in their morphology. Verrucaria subdevergens more often has pale brownish thallus and slightly longer periphysoids. Verrucaria difficilis has, on average, less-developed thallus and the perithecia and the spores slightly smaller.