Coenogonium is a fairly large genus of more than 90, mainly tropical species, characterised by biatorine (rarely zeorine), whitish, yellow or orange apothecia with a paraplectenchymatous exciple, a partially amyloid hymenium, thin-walled, unitunicate asci, 1-septate or rarely simple ascospores, and a trentepohlioid photobiont. Originally, it included only species with a filamentous-byssoid thallus, while crustose taxa were separated in the genus Dimerella. However, the discovery of some species which have both a filamentous and a crustose thallus, and the fact that Dimerella and Coenogonium have the same type of apothecia, while the morphological differences are due to the photobiont, led Lücking & Kalb (2000) to unite both genera under the older name Coenogonium. Molecular data (Kauff & Lutzoni 2002) confirm the monophyly of the genus, which is placed in the family Coenogoniaceae, as circumscribed by Lücking & Kalb (2000).
This is a key to the 3 species occurring in Italy (Nimis 2016), all of them formerly treated as Dimerella (see Alvarez & Carballal 2001), which were treated by Cannon & al. (2021).

References

Alvarez Andrés J., Carballal Durán R, 2001, The genus Dimerella (Gyalectales, Ascomycotina) in Peninsular Spain and Portugal. Nova Hedwigia, 73, 3-4: 409-418.
Cannon P., Malíček J., Sanderson N., Benfield B., Coppins B., Simkin J. 2021. Ostropales: Coenogoniaceae, including the genus Coenogonium. Revisions of British and Irish Lichens 3: 1-4.
Kauff F., Lutzoni F. 2002. Phylogeny of the Gyalectales and Ostropales (Ascomycota, Fungi): among and within order relationships based on nuclear ribosomal RNA small and large subunits. Mol. Phylogen. Evol., 25: 138-156.
Lücking R., Kalb K. 2000. Foliikole Flechten aus Brasilien (vornehmlich Amazonien), inklusive einer Checkliste und Bemerkungen zu Coenogonium und Dimerella (Gyalectaceae). Bot. Jahrb., 122: 1-61.
Nimis P.L. 2016. The Lichens of Italy. A Second Annotated Catalogue. EUT, Trieste, 739 pp.

Last modified: February, 15, 2022.

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