Revision of the Parmelia saxatilis group in Italy based on morphological, chemical, and molecular data

Abstract

Recent molecular studies on Parmelia revealed several new semi-cryptic and cryptic species, suggesting the existence of considerable genetic diversity within this genus that may not yet be expressed at the phenotypic level. This is the case of the two species Parmelia ernstiae and P. serrana that have been described in the P. saxatilis group from Europe and that are still poorly known in Italy. The main aim of this study is to shed light into the Italian distribution of these cryptic species on the basis of a systematic and taxonomic revision of exiccata and new specimens of the Parmelia saxatilis group collected along a biogeographical gradient through the Italian peninsula. In this revision, we combined morphological, chemical, and molecular data and evaluated their reliability for identification at the species level. Results indicate that P. saxatilis is the most widespread species and that P. ernstiae is much more widespread than previously thought. In contrast, P. serrana seems to be a rare species in Italy. Our results also indicate that the combined use of morphological and chemical data does not provide a reliable tool to discriminate the cryptic species of this group and that molecular data are thus indispensable for identification at the species level. Finally, our phylogenetic analysis supports the existence of an unrecognized diversity in parmelioid lichens that should be further investigated.