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RESEARCH PRODUCT

Biodiversity Patterns and Ecological Preferences of the Photobionts Associated With the Lichen-Forming Genus Parmelia

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The worldwide, ecologically relevant lichen-forming genusParmeliacurrently includes 41 accepted species, of which theParmelia sulcatagroup (PSULgp) and theParmelia saxatilisgroup (PSAXgp) have received considerable attention over recent decades; however, phycobiont diversity is poorly known inParmelias. lat. Here, we studied the diversity ofTrebouxiamicroalgae associated with 159 thalli collected from 30 locations, including nineParmeliaspp.:P. barrenoae, P. encryptata, P. ernstiae, P. mayi, P. omphalodes, P. saxatilis, P. serrana, P. submontana, andP. sulcata. The mycobionts were studied by carrying out phylogenetic analyses of the nrITS. Microalgae genetic diversity was examined by using both nrITS and LSU rDNA markers. To evaluate putative species boundaries, three DNA species delimitation analyses were performed onTrebouxiaandParmelia. All analyses clustered the mycobionts into two main groups: PSULgp and PSAXgp. Species delimitation identified 13 fungal and 15 algal species-level lineages. To identify patterns in specificity and selectivity, the diversity and abundance of the phycobionts were identified for eachParmeliaspecies. High specificity of eachParmeliagroup for a givenTrebouxiaclade 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 associated with 12Trebouxiaspp., meanwhile those of PSULgp interacted only with threeTrebouxiaspp. Variation-partitioning analyses were conducted to detect the relative contributions of climate, geography, and symbiotic partner to phycobiont and mycobiont distribution patterns. Both analyses explained unexpectedly high portions of variability (99 and 98%) and revealed strong correlations between the fungal and algal diversity. Network analysis discriminated seven ecological clusters. Even though climatic conditions explained the largest proportion of the variation among these clusters, they seemed to show indifference relative to climatic parameters. However, the cluster formed byP. saxatilisA/P. saxatilisB/Trebouxiasp. 2/Trebouxiasp. S02/Trebouxiasp. 3A was identified to prefer cold-temperate as well as humid summer environments.