KEYS TO THE LICHENS OF ITALY - 04) ACAROSPORA (with Caeruleum, Myriospora, Pleopsidium, and Timdalia)
Pier Luigi Nimis
Apparatus of images: Andrea Moro - Software and databases: Stefano Martellos

Acarospora in the broad sense was a large, cosmopolitan genus of mainly saxicolous species, still insufficiently known in Italy. The genus was restricted by Crewe & al. (2006) to a monophyletic group of taxa related to the type species, A. schleicheri, while the A. smaragdula-group and A. badiofusca were excluded from the genus in a strict sense. After the separation of Pleopsidium, the species of the A. smaragdula-group have been recently segregated into the genus Myriospora (Arcadia & Knudsen 2012, see also Roux & Navarro-Rosinés 2011, and Westberg & al. 2011), characterised by usually brown or grey areoles or squamules, slender paraphyses, a tall hymenium, and a photobiont layer interrupted by hyphal bundles, while A. heppii is now included into the genus Caeruleum, on the basis of important morphological characters. The monotypic genus Timdalia was segregated from Acarospora and classified in the Lecanoraceae mainly due to differences in the ascus apex construction, polyspored asci having been considered as an example of convergent evolution (Hafellner & Türk 2001). However, Wedin & al. (2005) demonstrated that the genus is closely related to Acarospora in the Acarosporaceae (see also Westberg & al. 2015). The A. badiofusca-group is likely to be segregated into its own genus. The thorough molecular study of Acarosporaceae by Westberg & al. (2015) showed that the occurrence of strongly black-pigmented (carbonised or melanised) ascomata has arisen secondarily and independently numerous times in the evolution of the group, so that the genera Sarcogyne and Polysporina are distinctly non-monophyletic, and the latter could prove to be even a synonym of Acarospora. Important recent contributions are those by Knudsen & Kocourková (2012, 2020a, 2020b) Knudsen & Nordin (2015), and Knudsen & al. (2010, 2013,2014, 2015, 2019, 2021). The present key includes 67 species; however, since the genus is not very well known in Italy, and several other species coud occur in the country, I suggest to also use the more comprehensive key by Roux & al. (2019).


Arcadia L., Knudsen. K. 2012. The name Myriospora is available for the Acarospora smaragdula group. Opuscula Philolich., 11: 19-25.
Crewe A.T., Purvis O.W., Wedin M. 2006. Molecular phylogeny of Acarosporaceae (Ascomycota) with focus on the proposed genus Polysporinopsis. Mycol. Res., 110: 521-526.
Hafellner J., Türk R. 2001. Die lichenisierten Pilze Österreichs - eine Checkliste der bisher nachgewiesenen Arten mit verbreitungsangaben. Stapfia, 76: 1-167.
Knudsen K., Kocourková J. 2012. Lichenological notes 4: A revision of Acarospora gallica (Acarosporaceae). Mycotaxon, 119: 373-380.
Knudsen K., Kocourková J. 2020a. Two poorly-known species of European Acarospora (Acarosporaceae). Herzogia, 33, 1: 1-8.
Knudsen K., Kocourková J. 2020b. Acarosporaceae of Belarus. Herzogia, 33, 2: 394-406.
Knudsen K., Nordin A. 2015. The lectotypification of Acarospora trachytica Jatta (Acarosporaceae), a rare species from Italy. Opuscula Philolich., 14: 90-92.
Knudsen K., Reeb V., Westberg M., Srikantha R., Bhattacharya D. 2010. Acarospora rosulata in Europe, North America and Asia. Lichenologist, 42, 3: 291-296.
Knudsen K., Sheard J.W., Kocourková J, Mayrhofer H. 2013. A new lichenicolous lichen from Europe and western North America in the genus Dimelaena (Physciaceae). Bryologist, 116, 3: 257-262.
Knudsen K., Kocourková J., Nordin A. 2014. Conspicuous similarity hides diversity in the Acarospora badiofusca group (Acarosporaceae). Bryologist, 117, 4: 319-328.
Knudsen K., Kocourková J., Nordin A., Sipman H.J.M. 2015. Acarospora cinerascens (Acarosporaceae), a poorly known species from the southern Central Alps (Italy and Switzerland). Herzogia, 28, 2: 690-696.
Knudsen K., Arcadia L., Kocourková J. 2019. Acarospora squamulosa, the correct name for A. peliocypha. Mycotaxon, 134, 2: 281-287.
Knudsen K., Kocourková J., Cannon P., Coppins B., Flechter A., Simkin J. 2021. Revisions of British and Irish Lichens.12. Acarosporaceae. British Lichen Society, ISSN 2634-7768, 25 pp.
Roux C., Navarro-Rosinés P. 2011. Trimmatothelopsis (Acarosporaceae, Ascomycota lichenisati), le nom légitime de Silobia. Bull. Soc. linn. Provence, 62: 167-187.
Roux C., Poumarat S., Gueidan C., Navarro–Rosines P., Monnat J.-Y., Houmeau J.M. 2019. La Acarosporaceae de Okcidenta Eŭropo. Bull. Soc. linn. Provence, 70: 107-167.
Wedin M., Wiklund E., Crewe A., Döring H., Ekman S., Nyberg Å., Schmitt I., Lumbsch H.T. 2005. Phylogenetic relationships of Lecanoromycetes (Ascomycota) as revealed by analyses of mtSSU and nLSU rDNA sequence data. Mycol. Res., 109, 2: 159-172.
Westberg M., Crewe A.T., Purvis O.W., Wedin M. 2011. Silobia, a new genus for the Acarospora smaragdula-complex (Ascomycota, Acarosporales) and a revision of the group in Sweden. Lichenologist, 43, 1: 7-25.

Last modified: September, 1, 2022

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