In spite of careful numerical taxonomic studies, the characters of Hymenelia and Ionaspis overlap considerably; the type of photobiont, which in the past was used to neatly separate the two genera, is now considered as irrelevant for their separation (see Lutzoni & Brodo 1995). For this reason, I prefer to treat here all species of Ionaspis under the older name Hymenelia. The genus is now placed in the Hymeneliaceae. Relevant keys are in Magnusson (1933), Clauzade & Roux (1985), Jørgensen (1989), Thüs & Schultz (2009), Wirth & al. (2013), and Cannon & al. (2025).

References

Cannon P., Fryday A., Coppins B., Aptroot A., Sanderson A., Simkin J. 2025. Hymeneliales, including Hymenelia and Tremolecia (Hymeneliaceae). Revisions of British and Irish Lichens, 46: 1-8.
Clauzade G., Roux C. 1985. Likenoj de Okcidenta Europo. Ilustrita determinlibro. Bull. Soc. Bot. Centre-Ouest, N. Ser., N. Spec. 7. Royan, 893 pp.
Jørgensen P.M. 1989. Notes on the lichen genus Ionaspis in Scandinavia. Graphis Scripta, 2: 118-121.
Lutzoni F.M., Brodo I.M. 1995. A generic redelimitation of the Ionaspis-Hymenelia complex. Syst. Bot., 20, 3: 224-258.
Magnusson A.H. 1933. A monograph of the lichen genus Ionaspis. Acta Horti Gothob., 8: 1-46.
Thüs H., Schultz M. 2009. Fungi: Lichens 1. In: Süßwasserflora Von Mitteleuropa. Spektrum Akademischer Verlag, Heidelberg, Germany. 223 pp.
Wirth V., Hauck M., Schultz M. 2013. Die Flechten Deutschlands. Stuttgart, Ulmer. 2 voll., 1244 pp.

Last modified: December, 26, 2025

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