This is a key to all species of Porpidia hitherto known to occur in Italy (see Nimis 2016), plus some species reported from the Alps outside Italian territory (see Nimis & al. 2018), also including the only species of the poorly known genus Stenhammarella, for a total of 20 species.
Porpidia is the largest segregate (c. 50 species) from the genus Lecidea in the Lecideaceae, being distinguished by the distinctive ascus-type and the larger, halonate ascospores. However, a recent molecular analysis of lecideoid lichens by Schmull & al. (2011) has shown that two Porpidia-species are nested within Lecidea s.str. (P. albocaerulescens and P. speirea). So far, the delimitation of both genera and species within each genus is still problematic and should be subjected to a comprehensive phylogenetic study (see also Buschbom & Mueller 2004). European species were treated by Hertel (1967, 1975) and Schwab (1986). A good key, which includes all species occurring in Italy, was published by Wirth & al. (2013).

References

Buschbom J., Mueller G. 2004. Resolving evolutionary relationships in the lichen-forming genus Porpidia and related allies (Porpidiaceae, Ascomycota). Mol. Phylog. Evol., 32: 66-82.
Hertel H. 1967. Revision einiger calciphiler Formenkreise der Flechtengattung Lecidea. Beih. Nova Hedwigia, 24: 1-155.
Hertel. H. 1975. Ein vorlaufiger Bestimmungsschussel fur die kryptothallinen, schwartzfruchtigen, saxicolen Arten der Sammelgattung Lecidea (Lichenes) in der Holarktis. Decheniana, 127: 37-78.
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.
Schwab A.J. 1986. Rostfarbene Arten der Sammelgattung Lecidea (Lecanorales). Revision der Arten Mittel- und Nordeuropas. Mitt. Bot. Staatssamml. München, 22: 221-476.
Schmull M., Miadlikowska J., Pelzer M., Stocker-Wörgötter E., Hofstetter V., Fraker E., Hodkinson B.P., Reeb V., Kukwa M., Lumbsch H.T., Kauff F., Lutzoni F. 2011. Phylogenetic affiliations of members of the heterogeneous lichen-forming fungi of the genus Lecidea sensu Zahlbruckner (Lecanoromycetes, Ascomycota). Mycologia, 103, 5: 983-1003.
Wirth V., Hauck M., Schultz M. 2013. Die Flechten Deutschlands. Stuttgart, Ulmer. 2 voll., 1244 pp.

Last modified: January, 2, 2023

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