Diplotomma venustum (Körb.) Körb.

Parerga Lichenol.: 179, 1860. Basionym: Diplotomma alboatrum var. venustum Körb. in Rabenh. - Flecht. Eur., 13: nr. 384, 1858.
Synonyms: Buellia alboatra var. venusta (Körb.) Th. Fr.; Buellia suevica Bertsch; Buellia venusta (Körb.) Lettau; Rhizocarpon alboatrum var. venustum (Körb.) Anzi; Rhizocarpon calcareum auct. ital. p.p.
Distribution: N - VG (Tretiach & al. 2007b), Frl, Ven, Lomb, Piem (Clerc & al. 1999), Emil (Fariselli & al. 2020), Lig (Bungartz & Nash 2004, Giordani & al. 2016). C - Tosc (Brackel 2015), Marc (Nimis & Tretiach 1999), Umb (Nimis & Tretiach 1999, Ravera & al. 2006), Laz (Nimis & Tretiach 2004), Abr (Recchia & Villa 1996, Nimis & Tretiach 1999, Gheza & al. 2021), Mol (Nimis & Tretiach 1999, Caporale & al. 2008). S - Camp (Aprile & al. 2003b, Nimis & Tretiach 2004), Pugl (Nimis & Tretiach 1999, Durini & Medagli 2002), Bas (Nimis & Tretiach 1999, Brackel 2011), Cal (Puntillo 1996), Si (Nimis & al. 1996b).
Description: Thallus crustose, episubstratic, white to pale grey, continuous to verrucose-areolate, very thick, forming orbicular patches to c. 4 cm in diam. Cortex colourless, indistinctly paraplectenchymatous; medulla chalky white, I-. Apothecia lecideine, first immersed then subsessile, 0.4-1.5 mm across, with an initially flat, then soon strongly convex, often slightly white-pruinose disc, a thin, soon excluded proper margin, and usually a pseudothalline margin in young apothecia. Proper exciple dark brown in section, not continuous with hypothecium; epithecium brown; hymenium colourless, K/I+ blue; paraphyses simple, 1-1.5 μm thick at base, the apical cells 2.5-4.5 μm wide; hypothecium pale brown. Asci 8-spored, clavate, with a thick apex, amyloid, with a distinct axial mass, Bacidia-type. Ascospores 3-septate, brown, ellipsoid, often slightly curved, 16-22 x 7-10 μm. Photobiont chlorococcoid. Spot tests: medulla K+ yellow then red (crystals), C-, KC-, P+ yellow, UV-. Chemistry: medulla with norstictic acid.
Note: this mild-temperate to Mediterranean lichen, at least when young, is a constant parasite on Protoparmeliopsis versicolor, reaching above treeline south of the Alps. Morphological and biological differences towards D. hedinii are so evident that the synonymisation of the two taxa proposed by Nordin (1996), based on samples from southern Sweden (!) and on chemical characters only, is not accepted here. See also note on D. hedinii and Roux & Gueidan (2002: 145-146).
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
paras Protoparmeliopsis versicolor

Commonnes-rarity: (info)

Alpine belt: absent
Subalpine belt: very rare
Oromediterranean belt: very rare
Montane belt: rare
Submediterranean belt: rather common
Padanian area: absent
Humid submediterranean belt: rather common
Humid mediterranean belt: rather rare
Dry mediterranean belt: rare


pH of the substrata:

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5

Solar irradiation:

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Aridity:

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5

Eutrophication:

(info)

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Poleotolerance:

(info)

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Altitudinal distribution:

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Felix Schumm – CC BY-SA 4.0
[14942], Germany, Baden-Württemberg, Kreis Esslingen, Weilheim, am Gipfel der Limburg, auf Kalksteinen, ca. 590 m. Leg. et det. Schumm 12.07.2009.



P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: TSB (32041)
2001/12/09



A. Moro; Owner: Department of Life Sciences, University of Trieste
Sicilia, TP, Erice, dintorni della città
2008.04.05



A. Moro; Owner: Department of Life Sciences, University of Trieste
Sicilia, TP, Erice, dintorni della città
2008.04.05



A. Moro; Owner: Department of Life Sciences, University of Trieste
Sicilia, TP, Erice, dintorni della città
2008.04.05



A. Moro; Owner: Department of Life Sciences, University of Trieste
Sicilia, TP, Erice, dintorni della città
2008.04.05



A. Moro; Owner: Department of Life Sciences, University of Trieste
Sicilia, TP, Erice, dintorni della città
2008.04.05



Felix Schumm – CC BY-SA 4.0
[14942], Germany, Baden-Württemberg, Kreis Esslingen, Weilheim, am Gipfel der Limburg, auf Kalksteinen, ca. 590 m. Leg. et det. Schumm 12.07.2009.



Felix Schumm – CC BY-SA 4.0
[14942], Germany, Baden-Württemberg, Kreis Esslingen, Weilheim, am Gipfel der Limburg, auf Kalksteinen, ca. 590 m. Leg. et det. Schumm 12.07.2009.



Felix Schumm – CC BY-SA 4.0
[14942], Germany, Baden-Württemberg, Kreis Esslingen, Weilheim, am Gipfel der Limburg, auf Kalksteinen, ca. 590 m. Leg. et det. Schumm 12.07.2009.



Felix Schumm – CC BY-SA 4.0
[14942], Germany, Baden-Württemberg, Kreis Esslingen, Weilheim, am Gipfel der Limburg, auf Kalksteinen, ca. 590 m. Leg. et det. Schumm 12.07.2009.



Felix Schumm – CC BY-SA 4.0
[14942], Germany, Baden-Württemberg, Kreis Esslingen, Weilheim, am Gipfel der Limburg, auf Kalksteinen, ca. 590 m. Leg. et det. Schumm 12.07.2009.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010.



P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: TSB (32041)
2001/12/09



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010



Felix Schumm – CC BY-SA 4.0
[16508],Germany, Baden-Württemberg, Kreis Göppingen, Gosbach- Bad Ditzenbach, Tierstein, 48,57461° N, 9,68471° E, 737 m, auf Kalkfelsen am Albrand. Leg. et det. Schumm 20.06.2010