This is a key to all species of Collemataceae known to occur in Italy (see Nimis 2016). The key also includes the former Collema fasciculare, which now belongs to Gabura in the Arctomiaceae (Otálora & Wedin 2013), Staurolemma omphalarioides in the Pannariaceae, and Leptochidium albociliatum in the Massalongiaceae, plus a few species which are known from neighbouring countries, for a total of 71 infrageneric taxa.
After the molecular study of the Collemataceae genera Collema and Leptogium by Otálora & al. (2014), the genus Collema s.str., formerly monographed by Degelius (1954, 1974) has been re-circumscribed to include only 40 species belonging to four morphologically similar informal infrageneric units (the nigrescens-, japonicum-, leptaleum-, and coilocarpum-groups), which, with a single exception, have transversely septate ascospores.
The other species of Collema s.lat. now belong to 6 different genera:
1) Blennothallia includes 4 species with a worldwide distribution but predominantly occurring in temperate regions. The genus is characterised by the distinct, partially paraplectenchymatous thallus anatomy, and corresponds to the Collema crispum-group of earlier authors. It is more closely related to Scytinium than to Collema s.str., forming a well-supported lineage together with Scytinium and Lathagrium.
2) Callome (including only C. multipartita), This genus, restricted to Europe, northern Africa and North America, is sister to Rostania but no unique morphological, anatomical and ecological similarities are shared by these two genera. The recognition of Callome as separate from Rostania was based on thallus habitus, ecology, ascospore shape and septation.
3) Enchylium (formerly the Collema tenax-group), characterised by swollen and plicate thallus lobes, and apothecia that usually have a distinct anatomy of the excipulum (euthyplechtenchymatous). Most of the 9 species are saxicolous or terricolous; the two epiphytic species (E. conglomeratum and E. ligerinum) were not included in the analysis of Otálora & al. (2014).
4) Lathagrium (the earlier Collema cristatum-group), differs from Collema s.str. in spore septation and size, and in being exclusively saxicolous/terricolous; it differs from Enchylium in characteristics of the lobes and of the proper exciple. The genus, with 10 species known, forms a well-supported sister clade to Scytinium.
5) Paracollema is a small genus of 2 species, recently created to accommodate the Collema italicum-group, and is distinguished from other Collemataceae by the very small asci and spores.
6) Rostania, characterised by minute thalli and cubic muriform spores, corresponds to the Collema occultatum-group of earlier authors. The genus, which includes 7 species, is mainly distributed in the temperate regions of the Northern Hemisphere (Europe and North America), with some representatives in subtropical Asia and Africa.
After the segretation of Scytinium by Otálora & al. (2014), Leptogium s.str., with c. 70 species, is now the largest genus within the Collemataceae, including large foliose, eucorticate, mainly epiphytic species with a wide distribution, but also species restricted to tropical regions where the diversity of the genus is greater. It differs from the other eucorticate genus (Scytinium) in lobe and thallus size, habitat and distribution. The genus Epiphloea, formerly included into the Heppiaceae, proved to belong to the Collemataceae and was placed into Leptogium s.str. by Schultz & al. (2015), in spite of the crustose thallus and the different ecology. Leptogium-species are mainly corticolous (rarely saxicolous) and mostly occur in the wet tropics and in humid temperate regions, while Scytinium-species are bryophilous or saxicolous/terricolous (rarely corticolous) and mainly occur in temperate regions.
Pseudoleptogium is a monospecific genus that may resemble some squamulose species of Scytinium, from which it differs in the presence of two well differentiated squamule types.
Scytinium includes c. 46 species formerly placed in three Leptogium-sections (sect. Homodium, Collemodium and Leptogium), and three groups formerly included in Collema (the fragrans-, callopismum- and leptogioides-groups). Most species occur in temperate regions of the Northern Hemisphere, and are very rare in tropical regions. Several species occurring in Italy were treated e.g. by Aragón & al. (2004), Jørgensen (2007), and Otálora & al. (2004). In some groups, species delimitation is still an open problem, and the revision of the Italian material of e.g. S. lichenoides s.lat. is much needed.

References

Aragón G., Martínez I., Otálora M.A.G. 2004. The lichen Leptogium subaridum, a new Mediterranean-NW American disjunction. Lichenologist, 36, 2: 163-165.
Degelius G. 1954. The lichen genus Collema in Europe, morphology, taxonomy and ecology. Symb. Bot. Upsal., 13, 2: 1-411.
Degelius G. 1974. The lichen genus Collema, with special reference to the extra-European species. Symb. Bot. Upsal, 20, 2: 1-215.
Jørgensen P.M. 2007. Arctomiaceae, Coccocarpiaceae, Collemataceae, Heppiaceae, Lichinaceae, Pannariaceae. Nordic Lichen Flora, Vol 3: Cyanolichens.
Nimis P.L. 2016. the Lichens of Italy. A second annotated Catalogue. EUT, Trieste, 739 pp.
Otálora M.A.G., Wedin M. 2013. Collema fasciculare belongs in Arctomiaceae. Lichenologist, 45: 295-304.
Otálora M.A.G., Aragòn G., Martínez I., Molina M.C. 2004. A new corticolous species of Leptogium (Collemataceae) from Spain. Lichenologist, 36, 3-4: 197-202.
Otálora M.A.G., Martinez I., Molina M.C., Aragón G., Lutzoni F. 2008. Phylogenetic relationships and taxonomy of the Leptogium lichenoides group (Collemataceae, Ascomycota) in Europe. Taxon, 57, 3: 907-921.
Otálora M., Jørgensen P.M., Wedin M. 2014. A revised generic classification of the jelly lichens, Collemataceae. Fungal Divers., 64, 1: 275-293.
Wedin M., Wiklund E., Jørgensen P.M., Ekman S. 2009. Slippery when wet: phylogeny and character evolution in the gelatinous cyanobacterial lichens (Peltigerales, Ascomycetes). Mol. Phylog. Evol., 53: 862-871.

Last modified: August, 28, 2023

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