Protoblastenia s.str. comprises only crustose species with apothecia encrusted by anthraquinones and with Psora-type asci containing non-septate ascospores. The genus proved to be close to Psora, both genera forming the core of the family Psoraceae. The number of recognized infrageneric taxa if of c. 30, all of which grow on limestone or other substrates with at least a low content of calcium; the Alps seem to be the centre of diversity for the genus (Kainz & Rambold 2004), with 18 infrageneric taxa recognized by Nimis & al. (2018). Several taxa are critical, and await further exploration.
This key includes all taxa known to occur in Italy (Nimis 2016), plus the following taxa known from neighbouring areas and to be looked for in Italy: P. calvella, P. laeta, P. szaferi, P. rupestris subsp. rhodothecia, for a total of 15 infrageneric taxa.

References

Kainz Ch., Rambold G. 2004. A phylogenetic study of the lichen genus Protoblastenia (Lecanorales, Psoraceae) in Central Europe. Bibl. Lichenol., 88: 267-299.
Nimis P.L. 2016. The lichens of Italy. A second annotated catalogue. EUT, Trieste, 740 pp.
Nimis P.L., Hafellner J., Roux C., Clerc P., Mayrhofer H., Martellos S., Bilovitz P.O. 2018. The Lichens of the Alps. An Annotated Catalogue. Mycokeys, 31: 1-634.

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