Protoblastenia compressa Pykälä & Myllys, 2025

Pykälä, Juha & Myllys, Leena, 2025, Unexpected species richness of the lichen genus Protoblastenia (Lecanorales, Psoraceae) in Finland, MycoKeys 124, pp. 193-226 : 193-226

Protoblastenia compressa Pykälä & Myllys sp. nov.

Fig. 2 C

Diagnosis.

Differs from P. pseudocompressa in having plane to slightly convex apothecia.

Type.

Finland • Varsinais-Suomi, Parainen (Korppoo), Elfsjö, Hummelskär Island, close by shore of the Baltic Sea , calcareous rock outcrop, on shady 1 m high NE-facing wall, 5 m a. s. l., 60°08'N, 21°24'E, 31 July 2009, J. Pykälä 35585 ( H 9250940 – holotype, GenBank accession number: PV 766659 ) .

Description.

Thallus white to pale grey, continuous, rimose to rarely areolate, areoles 0.2–0.8 mm, ca. 0.01–0.15 mm thick, K-, C-, UV- to UV + bluish-white, algal cells 4–9 μm. Apothecia yellow, yellow-orange to orange, 0.2–0.8 mm, plane to slightly convex, 1 / 4–1 - immersed in thallus, occasionally leaving shallow pits, K + violet; ca. 20–190 apothecia / cm 2. Epihymenium orange-brown, 12–18 μm thick, K + violet. Hymenium 50–60 μm thick. Hypothecium colourless to yellow, ca. 40–100 μm thick. Paraphyses ca. 2–2.5 μm thick, apex not thickened to slightly thickened, sparingly branched and anastomosing. Ascospores 0 - septate, (8.6 –) 9.8–11.4 – 12.6 (– 13.5) × (4.8 –) 5.1–5.9 – 6.7 (– 7.4) μm (n = 45).

Habitat and distribution.

This species has ca. 40 known localities in the hemi-boreal vegetation zone in SW Finland (seven localities confirmed by ITS). It grows on calcareous rocks and in lime quarries, often on N-facing walls. It seems to prefer shady habitats. In the SW archipelago of Finland, P. compressa may be the most common Protoblastenia species. Typical companion species are Bagliettoa baldensis (A. Massal.) Vězda s. lat, Clauzadea monticola , Lepraria finkii (B. de Lesd.) R. C. Harris , Polyblastia abscondita (Nyl.) Arnold , Sagiolechia protuberans (Ach.) A. Massal. , Thelidium decipiens (Nyl.) Kremp. , T. incavatum Mudd , Verrucaria foveolata (Flörke) A. Massal. , V. muralis , V. nigrescens s. lat. and V. viridula (Schrad.) Ach.

Etymology.

The name refers to the flattened apothecia of the species.

Notes.

The species is characterised by plane to slightly convex apothecia. Protoblastenia pseudocompressa is a sister species with a rather similar morphology. However, P. pseudocompressa often has convex apothecia which have not been seen in P. compressa . The occurrence of Protoblastenia pseudocompressa has been confirmed only in the Kuusamo-Salla area ca. 800 kilometres north from the distribution area of P. compressa . Protoblastenia incrustans differs in having apothecia that leave pits ( P. compressa rarely leaves shallow pits). Protoblastenia coniasis differs in having a yellow thallus that gradually turns brownish-rose in the herbarium ( Poelt 1957). Protoblastenia compressa may also be difficult to separate from P. rupestris , even though they are not closely related. However, P. compressa usually has thinner apothecia and a thinner thallus which is rarely areolate (mostly areolate in P. rupestris ). ITS may sometimes be needed for unambiguous identification of P. compressa .

Other sequenced specimens.

Finland • Varsinais-Suomi, Kemiönsaari (Västanfjärd), Södersundvik, Näsudden , calcareous rock outcrop on shore of the Baltic Sea, cliff, on N-facing wall, rather scarce, 12 m a. s. l., 60°03'N, 22°46'E, 25. 8. 2009, J. Pykälä 36521 ( H) ; • Parainen (Korppoo), Elfsjö, Stora Limskär Island , abandoned lime quarry, beneath N-facing wall, bottom, on pebbles, 4 m a. s. l., 60°09'N, 21°26'E, 22. 6. 2010, J. Pykälä 38349 ( H) ; • Parainen (Korppoo), Åfvensår, Ronudden , abandoned lime quarry, on NW-facing wall, 2 m a. s. l., 60°18'N, 21°32'E, 2. 7. 2010, J. Pykälä 38646 ( H) ; • Parainen (Korppoo), Åfvensår, Ronudden , abandoned lime quarry on shore of the Baltic Sea, on overhanging NW-facing wall, 2 m a. s. l., 60°17'N, 21°32'E, 15. 7. 2010, J. Pykälä 38965 ( H) ; • Salo (Suomusjärvi), Rautsuo, 200 m NE of Kukutin , herb-rich forest, abandoned lime quarry, on NW-facing wall, 85 m a. s. l., 60°21'N, 23°37'E, 28. 9. 2010, J. Pykälä 41376 ( H) ; • Parainen, Skräbböle, Skräbböle lime quarry, by the lime quarry, N-slope, on stone, 24 m a. s. l., 60°17'N, 22°17'E, 5. 10. 2010, J. Pykälä 41511 b ( H) ; • Parainen, Attu, Skötudden SW , abandoned lime quarry on shore of the Baltic Sea, on NE-facing wall, 2 m a. s. l., 60°11'N, 22°18'E, 16. 6. 2011, J. Pykälä 42124 ( H) .

Figures

Figure 2. A. Protoblastenia arupii (holotype); B. P. borealis (holotype); C. P. compressa (holotype); D. P. dolomitica (holotype). Scale bars: 0.5 mm.