The worldwide, ecologically relevant lichen-forming genus Parmelia currently includes 41 accepted species, of which the Parmelia sulcata group (PSULgp) and the Parmelia saxatilis group (PSAXgp) have received considerable attention over recent decades. Despite the fact that several mycological studies focused on solving phylogenetic relationships within this genus, they are still under revision. In addition, phycobiont diversity is poorly known in Parmelia s. lat. Here, we studied the diversity of Trebouxia microalgae associated with 159 thalli collected from 35 locations, including nine Parmelia spp.: P. barrenoae, P. encryptata, P. ernstiae, P. mayi, P. omphalodes, P. saxatilis, P. serrana, P. submontana and P. sulcata. The mycobionts were studied by carrying out phylogenetic analyses of the ITS rDNA. The genetic diversity of Trebouxia spp. was screened by using the ITS rDNA and LSU rDNA markers. Species delimitation analyses were performed to estimate putative species boundaries in the Trebouxia and Parmelia datasets. All the mycobiont analyses clustered into the main groups: PSULgp/PSAXgp. Species delimitation showed 13 fungal and 15 algal species scenarios. Diversity and abundance of Trebouxia spp. was assessed for each Parmelia species to identify patterns in specificity and selectivity at the species level. High specificity of each Parmelia group for a given Trebouxia clade was observed; PSULgp associated only with "clade I" and PSAXgp with "clade S". However, the degree of specificity is different within each group, since the PSAXgp mycobionts were less specific and associate with 12 Trebouxia spp., meanwhile those of PSULgp interacted only with three Trebouxia spp. To elucidate the relative influence on microalgal genetic variability of the following factors: mycobiont identity, geographic distribution, climate and substrate/habitat, analyses of partitioned variation were carried out. Mycobiont identity and climate were found to be the main drivers for the genetic differences in symbiotic Trebouxia linked to Parmelia holobionts. Funding: PROMETEO/2017/039
Complete tool for submission, evaluation and publication of proceedings for scientific events.
