Verrucaria karelica Vain., Acta Soc. Fauna Flora Fenn. 49(2): 46, 1921

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 karelica Vain., Acta Soc. Fauna Flora Fenn. 49(2): 46, 1921

Type.

Russia, Karelia Onegensis, Mundjärvi, supra saxa dolomitica cinerea, J. P. Norrlin (H-NYL 3146!, H!, syntypes).

Description.

Prothallus absent. Thallus white, grey or pale greyish-brown, endolithic or thinly epilithic, farinose, algal cells 5-8 mm, contiguous conspecific thalli often separated by dark lines, 0.13-0.22 mm wide. Perithecia 0.07-0.37 mm, (1/2-)3/4-1-immersed, leaving shallow to usually deep pits in the rock, surrounded by a thalline collar; 40-80 perithecia/cm2. Ostiole pale or dark, plane or depressed ca. 20-40(-60) mm wide. Involucrellum apical or covering half of the exciple, 50-70 mm thick, appressed to the exciple or diverging from the exciple. Exciple 0.21-0.28 mm in diam., wall dark brown to black, ca. 20-31 mm thick. Periphysoids ca. 30-50 × 2-2.5(-3) mm. Asci ca. 66-84 × 26-33 mm, 8-spored. Ascospores 0-septate, (23.2-)26.2-27.9-29.5(-31.3) × (10.3-)11.7-12.3-13.0(-14.1) mm (n = 63), perispore not seen, but may have vanished during storage.

Habitat and distribution.

This species is known from Finland only from the Oulanka area in the biogeographical province of Koillismaa in NE Finland where it grows on dolomite rocks. It seems to occur in fairly shady habitats.

Other specimens examined.

Finland. Koillismaa, Salla, Oulanka National Park, Savikoski 300 m W, Pinus sylvestris -forest, steep N-slope, dolomite rock outcrop, on N-facing wall, 180 m alt., 66°25'N, 29°10'E, 10 Aug 2010, J. Pykälä 39625 (H); Kuusamo, Oulanka, Putaanoja, 500 m W-NW of Hautala, NE-slope, dolomite rock outcrop, on 50 cm high SW-facing wall, scarce, 232 m alt., 66°22'N, 29°25'E, 15 Aug 2010, J. Pykälä 39991 (H); Kuusamo, Oulanka National Park, Kiutaköngäs N, steep S-slope, Pinus sylvestris -dominated forest, dolomite rock outcrop, on SW-facing wall, 182 m alt., 66°22'N, 29°19'E, 19 Aug 2010, J. Pykälä 40325 (H); Salla, Oulanka National Park, W of Savikoski, cliff, dolomite rock outcrop, on NE-facing wall, scarce, 185 m alt., 66°25'N, 29°10'E, 17 Aug 2010, J. Pykälä 40235 (H).

Notes.

The type specimens of V. karelica have epilithic thalli and contiguous conspecific thalli are separated by dark lines. None of the Finnish specimens has both epilithic thalli and dark lines. However, one of the sequenced specimens has epilithic thalli and another specimen has dark lines. Thus, based on morphology, this entity probably belongs to V. karelica . The type locality of V. karelica (Vainio 1921) is situated rather close to the Oulanka area, suggesting that the species would probably occur in the Oulanka area. The species is closely related to V. devergens and V. subdevergens . V. devergens and V. karelica may not be unambiguously separated by morphology only. Verrucaria devergens usually has endolithic thalli and several specimens lack an involucrellum. Verrucaria karelica may be absent from subaquatic habitats unlike V. devergens which often grows on river shores. Verrucaria subdevergens has an involucrellum usually exceeding half of the exciple height. The species is also difficult to be separated from several other species of Verrucaria belonging to the Thelidium group. Verrucaria cavernarum , V. difficilis and V. subtilis always lack dark lines between contiguous conspecific thalli and the spores are smaller. Verrucaria kuusamoensis usually has an involucrellum exceeding half of the exciple.