Verrucaria bifurcata Pykaelae , Kantelinen & 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 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) × (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, Länsi-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. Pykälä 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 × 1.5-2.5 mm. Asci 60-104 × 22-33 mm, 8-spored. Ascospores 0-septate, (20.6-)23.8-25.8-27.8(-30.3) × (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, Särkisalo, Förby, E of Vähämaankaula, abandoned lime quarry, beneath NW-facing wall, on stone, 7 m alt., 60°05'N, 22°52'E, 23 July 2008, J. Pykälä 33120 (H); Länsi-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. Pykälä 37228 (H); Etelä-Savo, Kerimäki, Ruokojärvi, Pitkäniemi, abandoned lime quarry, on NE-facing wall, 90 m alt., 61°56'N, 29°00'E, 15 Sept 2011, J. Pykälä 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 ( Pykälä 2013). However, the type of V. adelminienii is not identifiable ( Pykälä 2016). Furthermore, the spore size in the original description ( Zschacke 1933) is smaller than the spore size in the Finnish specimen.

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).