KEYS TO THE LICHENS OF ITALY - 57) ASPICILIOID LICHENS
Pier Luigi Nimis
Apparatus of images: Andrea Moro - Software and databases: Stefano Martellos
Aspicilioid lichens are a very heterogeneous group of lichens characterized by a trebouxioid photobiont and lecanorine apothecia which are immersed in the thallus. The core of this group is constituted by Aspicilia s.lat., a genus of the Megasporaceae which has been recently split into different genera (see later). Superficially similar, but taxonomically unrelated species which are usually keyed out together with Aspicilia s.lat. belong to the genera Amylora, Aspilidea, Bellemerea, Eiglera, Immersaria, Koerberiella, and in part Rimularia.
A molecular revision of Aspicilia s.lat. was carried out by Nordin & al. (2010), who proposed a division of into five genera. The old names Circinaria and Sagedia were reintroduced for groups not including A. cinerea, the type species of Aspicilia. The small genus Megaspora was maintained, although it proved to be closely related to Circinaria, while Lobothallia appeared as the sister group of the other Megasporaceae genera. Aspicilia recedens and A. farinosa were transferred to Lobothallia, and further species belonging to the old subgenus Pachyothallia were added to this genus by Roux (2012). As a consequence Lobothallia, that was originally established for species with a lobate thallus, is now characterised by immersed to appressed or constricted-sessile apothecia, asci with an non-amyloid tholus (Aspicilia-type), unbranched paraphyses, simple, hyaline spores and mainly bacilliform conidia; lobes are distinct in some species, while other species have indistinct lobes. More recently, the genus Teuvoa was created by Sohrabi & al. (2013a) for the Aspicilia uxoris-group, and the genus Aspiciliella was resurrected for the Aspicilia intermutans-group (Zakeri & al. 2017). Unfortunately, only a part of the many species present in Italy, were molecularly analysed, so that their generic position still awaits clarification. The distinction between Aspicilia s.str. and Sagedia has been questioned by several authors (see e.g. Miadlikowska & al. 2014), and Roux & coll. (2020) consider Aspiciliella, Circinaria, Megaspora and Sagedia as subgenera of Aspicilia, accepting only Lobothallia as an independent genus. While basically sympathizing with a broad concept of Aspicilia, here I tentatively follow the narrow generic concepts, provisionally leaving most of the unresolved species into Aspicilia.
Other aspicilioid genera not belonging to Megasporaceae are:
1) Amylora - A monotypic genus of the Trapeliaceae including a species formerly treated as an Aspicilia, but differing in important chemical and morphological characters, especially the ascus type, occurring on steeply inclined to vertical surfaces of siliceous rocks, hitherto reported only from the Alps. For further details see Rambold (1994).
2) Aspilidea - Another monotypic genus segregated from Aspicilia, which is not a member of Megasporaceae, but seems to be more closely related to Ochrolechiaceae (Nordin & al. 2010).
3) Bellemerea - As re-defined by Calatayud & Rambold (1998), this genus is characterised by the following combination of characters: thallus whitish, greyish, ochraceous to rusty coloured, without a distinct epinecral layer, with the norstictic acid chemosyndrome in some species, asci of Bellemerea-type, ascospores with an amyloid inner wall layer and a distinctly halonate perispore (see also Clauzade & Roux 1984). The genus, which includes c. 8 species, is currently placed in the Lecideaceae. Most species occur in arctic-alpine habitats, and some of them are very closely related.
4) Eiglera - This genus with 2 species was often considered to be closely related to Hymenelia and Ionaspis, differing in the amyloid apical dome of the asci. However, Miadlikowska & al. (2014) showed that it is more closely related to the Acarosporaceae, in which it was included by Jaklitsch & al. (2016).
5) Immersaria - A genus of the Lecideaceae with 7 species in both Hemispheres, resembling Porpidia, which has a better developed exciple and lacks brown pigments in the cortex.
6) Koerberiella Stein - A genus of the Lecideaceae with 2 species, distinguished from primarily by the non-amyloid ascospore walls, and from other genera by the presence of a thalline exciple. Sterile forms were named differently by different authors.
Aspicilioid lichens, and especially Aspicilia s.lat. are among the most difficult groups of crustose lichens, many species showing a remarkably high morphological and chemical variation. Furthermore, on one hand, many species were described, especially from the Alps, which are known from a few collections only, while several species described from Northern Europe were reported from the Alps, whose conspecificity with northern material still has to be confirmed. On the other hand, several new species have been described or re-surrected in recent times from Southern Europe on the basis of fine anatomical differences, whose distribution is still very poorly known (see e.g. Bertrand & Roux 2013, Owe-Larsson & al. 2011, Roux & al. 2011, 2016, Sohrabi & al. 2013 a, ,b, Paukov & al. 2016, 2019, Roux & Coll. 2020).
This key, which will be tested an modified accordingly in the following months, is a first attempt to provide an overview on Aspicilioid lichens which could potentially occur in Italy. It includes all species which were reported from the country (Nimis 2016), several species which are known from the Alps outside the Italian territory (see Nimis & al. 2018), and several recently-described or resurrected species which are likely to occur also in Italy, for a total of 87 infrageneric taxa.
Acknowledgments: I am grateful to C. Roux for critical remarks on the manuscript, and to S. Poumarat and M. Bertrand for allowing me the use of their photos of some recently-described species.
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Last modified: March, 8, 2021
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