Verrucaria subdevergens Pykaelae & Myllys, 2020

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 subdevergens Pykaelae & Myllys sp. nov. Fig. 2F

Diagnosis.

Differing from V. devergens by longer involucrellum, morphologically difficult to separate from V. kuusamoensis , but the sequence divergence in ITS 5.4-6.0%.

Holotype.

Finland, Koillismaa, Kuusamo, Oulanka National Park, Taivalköngäs, shore of Oulankajoki river, dolomite rock outcrop, on gentle NE-slope, 165 m alt., 66°24'N, 29°11'E, 25 Aug 2011, J. Pykälä 45109 (holotype: H9205097, GenBank accession number: MT229783).

Description.

Prothallus absent. Thallus white, grey, ochraceous or pale greyish-brown, endolithic to thinly epilithic, continuous to irregularly rimose, in one specimen contiguous conspecific thalli separated by a dark line. Perithecia 0.21-0.42 mm, 1/2-3/4-immersed, leaving shallow to deep pits in the rock, often surrounded by a thallus collar, in one specimen, thalline covered except apex, thalline cover 8-20 mm thick; 80-120 perithecia/cm2. Ostiole inconspicuous, tiny, pale to dark, plane or depressed, ca. 20-40 mm wide. Involucrellum covering half of the exciple or to the exciple base, in few perithecia may envelope the exciple, 30-80 mm thick, in one specimen, often apically thickened to 50-70 mm thick, appressed to the exciple. Exciple 0.21-0.34 mm in diam., wall blackish-brown, ca. 15-25 mm thick. Periphysoids ca. 25-50 × 1.5-2 mm. Asci 82-94 × 27-33 mm, 8-spored. Ascospores 0-septate, (23.0-)25.4-28.2-31.0(-34.9) × (11.2-)12.0-13.0-13.9(-15.2) mm (n = 83), perispore 1-1.5 mm thick.

Habitat and distribution.

All three finds are from the Oulanka area in NE Finland where the species grows on dolomite rock outcrops and on a dolomite boulder.

Etymology.

The species is close to V. devergens .

Other specimens examined.

Finland. Koillismaa, Kuusamo, Oulanka National Park, Kiutaköngäs 400 m N, Pinus sylvestris -herb-rich forest, small dolomite rock outcrop, on small S-facing wall, 165 m alt., 66°22'N, 29°19'E, 3 Aug 2010, J. Pykälä 39128 (H); Kuusamo, Oulanka National Park, Taivalköngäs, shore of Oulankajoki river, Picea abies -dominated herb-rich forest, dolomite rock outcrop, NE-slope, on dolomite boulder, 174 m alt., 66°24'N, 29°11'E, 20 Aug 2011, J. Pykälä 44550 (H).

Notes.

This species is close to V. devergens and V. karelica , based on the ITS phylogeny. It differs from these species in a longer involucrellum mainly exceeding half of the exciple. Morphologically, V. subdevergens is most difficult to separate from V. kuusamoensis , which tends to have shorter periphysoids and the thallus is more often white.

Figures

Figure 2. Habitus of the new Verrucaria species A V. bifurcata (holotype) B V. cavernarum (holotype) C V. difficilis (holotype) D V. fuscozonata (holotype) E V. kuusamoensis (holotype) F V. subdevergens (holotype) G V. vacillans (holotype). Scale bars: 1 mm (A-D), 0.5 mm (E-G).