Cetrariod lichens presently make up a well-distinct clade within the Parmeliaceae (Divakar & al. 2017). In the past, the delimitation of this group was mainly based on morphological characters, so that also genera belonging to the Parmelioid clade, such as Cetrelia W.L. Culb. & C.F. Culb. and Platismatia W.L. Culb. & C.F. Culb. were included (Nelsen & al. 2011). Within the group, genera have been split so much, that many of them contained only a few species, while some other genera in the same family have an excessive number of species (e.g. Xanthoparmelia, with over 800 species). The phylogeny presented by Thell et al. (2009) showed that several genera had to be synonymized, to avoid describing new genera in a group that already had a very narrow genus concept. Two alternatives remained. One was to include all of the c. 80 species worldwide, excluding Dactylina Nyl. and Cornicularia (Schreb.) Hoffm., in a single large genus, Cetraria Ach. The other, according to cladistic rules, was to keep two genera, Cetraria and Nephromopsis Müll Arg., with a large and similar morphological variation in both groups, but usually with different shaped conidia: the Cetraria-clade has conidia with one swelling, while the Nephromopsis-clade has, almost entirely, conidia with two more-or-less apical swellings (Thell & al. 2005, 2009). Here, I follow the suggestion by Divakar & al. (2017) and Thell & al. (2018) to synonymise Allocetraria Kurok. & M. J. Lai , Cetrariella Kärnefelt & A. Thell , Usnocetraria M.J. Lai & J.C. Wei and Vulpicida E. Mattsson & M.J. Lai with Cetraria, and Arctocetraria Kärnefelt & Thell, Flavocetraria Kärnefelt & A. Thell, Tuckermannopsis Gyeln., and Tuckneraria Randlane & A. Thell with Nephromopsis. However, if the cetrarioid core group would be accepted as a single genus, as it was not long ago, it would be perfectly monophyletic under a single genus, Cetraria.
The present key includes all species of the cetrarioid group (plus Platismatia glauca) known to occur in Italy (Nimis 2016), plus three species (Cetraria crispiformis, C. delisei, C. sorediella) known from neighbouring areas and to be looked for in Italy (Nimis & al. 2018), for a total of 25 species.

References

Divakar P. K., Crespo A., Kraichak E., Leavitt S. D., Singh G., Schmitt I,. Lumbsch T.H. 2017. Using a temporal phylogenetic method to harmonize family and genus‐level classification in the largest clade of lichen‐forming Fungi. Fungal Diversity 84: 101-117. 2017.
Nelsen M.P., Chavez N., Sackett-Hermann E., Thell A., Randlane T., Divakar P.K., Rico V.J., Lumbsch H.T. 2011. The cetrarioid core group revisited (Lecanorales: Parmeliaceae). Lichenologist, 43, 6: 537-551.
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.
Thell A., Randlane T., Saag A., Kärnefelt I. 2005b. A new circumscription of the lichen genus Nephromopsis (Parmeliaceae, lichenized Ascomycetes). Mycol. Prog., 4, 4: 303-316.
Thell A., Högnabba F., Elix J.A., Feuerer T., Kärnefelt I., Myllys L., Randlane T., Saag A., Stenroos S., Ahti T., Seaward M.R.D. 2009. Phylogeny of the cetrarioid core (Parmeliaceae) based on five genetic markers. Lichenologist, 41, 5: 489-511.
Thell A., Kärnefelt I., Seaward M.R.D. 2018. Splitting or synonymizing – genus concept and taxonomy exemplified by the Parmeliaceae in the Nordic region. Graphis Scripta, 30, 6: 130-137.

Last modified: June, 21, 2024

Project Dryades, Department of Life Sciences, University of Trieste - CC BY-SA 4.0