Verrucaria cavernarum 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 cavernarum Pykaelae & Myllys sp. nov. Fig. 2B

Diagnosis.

Species morphologically somewhat similar to V. subtilis , ascospores slightly larger: (23-)25-30(-34) × (10-)11-13(-14) mm and the ITS sequence divergence between the species is 2.8-3.4%.

Holotype.

Finland. Koillismaa, Kuusamo, Oulanka National Park, Mataraniemi, shore of Oulankajoki river, treeless stony river shore, on dolomite stones, 145 m alt., 66°22'N, 29°20'E, 26 Aug 2011, J. Pykälä 45168 (H9205102, GenBank accession number: MT229725).

Description.

Prothallus absent. Thallus grey to pale greyish-brown, endolithic or thinly epilithic, continuous, 20-80 mm thick, algal cells 5-8 mm. Perithecia 0.15-0.28 mm in diam., 1/2-1-immersed, leaving shallow to deep pits in the rock, often surrounded by thallus collar, few perithecia thinly thalline covered; 80-160 perithecia/ cm2. Ostiole inconspicuous, dark, plane or depressed. Involucrellum apical to covering half of the exciple, in one specimen also few longer involucrella almost reaching the exciple base level present, 30-60 mm thick, appressed to the exciple or slightly diverging from the exciple. Exciple 0.16-0.32 mm, wall dark brown or black, ca. 15-25 mm thick. Periphysoids (25-)30-40(-50) × 1.5-2.5 mm, branching. Asci 8-spored. Ascospores 0-septate, two 1-septate spores seen in one specimen, (23.1-)25.1-27.5-29.8(-34.1) × (9.8-)10.7-11.6-12.6(-13.7) mm (n = 111), perispore 1 mm thick.

Habitat and distribution.

Two specimens of the species are from SW Finland and one specimen from NE Finland. The three sequenced specimens are from different kinds of habitats: dolomite stone on river shore (apparently periodically submerged), calcareous rock on seashore (perhaps not submerged) and in a lime quarry on pebbles. The species may prefer more humid (but preferably sun-exposed?) habitats than the other species in the V. subtilis complex.

Etymology.

The perithecia of the species leave shallow to deep pits in the rock when decayed.

Other specimens examined.

Finland. Varsinais-Suomi, Raasepori (Karjaa), Knapsby, Mustio lime quarry, deciduous forest on lime quarry waste, on pebbles, 45 m alt., 60°10'N, 23°49'E, 2 July 2009, J. Pykälä 34527 (H); Länsi-Turunmaa ( Iniö), Söderby, Biskopsö island, calcareous rock outcrop on shore of the Baltic Sea, on N-slope, scarce, 7 m alt., 60°20'N, 21°28'E, 9 June 2010, J. Pykälä 37975 (H).

Notes.

The species cannot be morphologically separated with certainty from the other species of the V. subtilis complex. It is most difficult to separate from V. subtilis . On average, V. cavernarum has slightly longer (mean 2.3 mm longer than in V. subtilis ) and broader (mean 1.1 mm broader than in V. subtilis ) spores and pale exciples have not been found.

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).