Notes:
Code: Bot_1360/2021-DSC06774
Habitat: Light mountain Fagus sylvatica forest, slightly inclined mountain slope, southeast aspect, calcareous, colluvial ground, in half shade, partly protected from direct rain; average precipitations ~ 3.000 mm/year, average temperature 7-9 deg C, elevations 560 m (1.850 feet), alpine phytogeographical region.
Substratum: Bare calcareous rock.
Place: Lower Trenta valley, right bank of river Soča; between villages Soča and Trenta; right bank of river Soča, above the main road and the river near Matevž farmhouse, Trenta 1, East Julian Alps, Posočje, Slovenia EC.
Comment: Verrucaria nigrescens is a very common, circumglobal lichen growing mostly on calcareous rocks. It is common in the Trenta valley too. Its thallus is superficial, not immersed into the rock (endolithic) as with many other Verrucaria species and relatively thick (0.3 – 0.5 mm). From far it looks like a black tar stain frequent on coastal rocks. From close one can see that the thallus is cracked into fine, irregular areoles, which are smaller than 1 mm. In the cracks among them black prothallus can be seen. Some of the areoles show the upper most part of immersed perithecia. When the thallus is wet it looks quite differently. The cracks in the thallus disappear and the perithecia tips look differently than in the dry state.

Camera: Nikon D700 / Nikkor Micro 105mm/f2.8 and Sony ILCE6000 / Carl Zeiss Vario-Tessar E 16-70 mm/f4

Images

Dry conditions.
Dry conditions.
Dry conditions.
Dry conditions.
Dry conditions.
Wet conditions.
Wet conditions.

Proposed Names

85% (1)
Recognized by sight: Very common, characteristically cracked when dry, on bare calcareous rock.
Used references: (1) F.S. Dobson, Lichens, The Richmonds Publishing Ca.LTD (2005), p 456.
(2) C.W.Smith, et all, The lichens of Great Britain and Ireland,The British Lichen
Society,(2009), p 953.
(3) V. Wirth, Die Flechten Baden-Württembergs, Teil.2., Ulmer (1995), p 967.

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