Pier Luigi Nimis
Parmotrema is characterised by foliose thalli forming short and broad, often ciliate lobes, a pored epicortex, cylindrical conidia, a usually wide bare marginal zone on the lower surface, and the intermediate type of lichenan between Cetraria- and Xanthoparmelia-type lichenan. Currently the genus comprises c. 300 species which occur mostly in the tropics, especially in the Pacific Islands and South America. Seven species are known to occur in Italy, all of them bound to rather humid microclimatic conditions. The most common species is P. perlatum, the rarest are P. hypoleucinum and P. robustum, which are confined to a few undisturbed sites, mainly along the Tyrrhenian coasts.
Recent molecular phylogenetic analyses of the lichen family Parmeliaceae have revealed that the members of the Parmelia crozalsiana-group form a sister clade to a clade containing members of the genus Parmotrema. The four species in this group were classified first in Parmelia, then in Pseudoparmelia, and later in Canoparmelia, until they were assigned to the newly created genus Crespoa (Lendemer & Hodkinson 2012). According to Kirika & al. (2016), however, they are best treated within a subgenus of Parmotrema.
This key includes 10 species (incl. Crespoa), one of which should be looked for in Italy (Nimis 2016).

Last modified: January, 12, 2023