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

ABSTRACT: 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; however, phycobiont diversity is poorly known in Parmelia s. lat. Here, we studied the diversity of Trebouxia microalgae associated with 159 thalli collected from 30 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 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 on Trebouxia and Parmelia. 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 each Parmelia species. 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 associated with 12 Trebouxia spp., meanwhile those of PSULgp interacted only with three Trebouxia spp. 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 by P. saxatilis A/P. saxatilis B/Trebouxia sp. 2/Trebouxia sp. S02/Trebouxia sp. 3A was identified to prefer cold-temperate as well as humid summer environments.

SUBMITTER: Moya P

PROVIDER: S-EPMC8739953 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:To evaluate the importance of morphological and chemical characters used in the recognition of species within the Parmelia omphalodes group, we performed phylogenetic, morphological and chemical analyses of 335 specimens, of which 34 were used for molecular analyses. Phylogenetic analyses, based on ITS rDNA sequences, show that P. pinnatifida is distinct from P. omphalodes and the most important difference between those species is the development of pseudocyphellae. In P. pinnatifida, they are mostly marginal and form white rims along lobes margins, but laminal pseudocyphellae can develop in older parts of thalli and are predominantly connected with marginal pseudocyphellae. In contrast, in P. omphalodes laminal pseudocyphellae are common and are predominantly not connected to marginal pseudocyphellae. Chemical composition of secondary lichen metabolites in both analysed species is identical and therefore this feature is not diagnostic in species recognition. Few samples of P. discordans, species morphologically similar to P. omphalodes and P. pinnatifida, were also included in the analyses and they are nested within the clade of P. omphalodes, despite the different chemistry (protocetraric acid present versus salazinic acid in P. omphalodes). All taxa of the P. omphalodes group occupy similar niches, but their potential distributions are wider than those currently known. The absence of specimens in some localities may be limited by the photobiont availability. Parmelia omphalodes and P. pinnatifida are moderately selective in photobiont choice as they form associations with at least two or three lineages of Trebouxia clade S. Parmelia pinnatifida, as well as P. discordans are associated with Trebouxia OTU S02 which seems to have a broad ecological amplitude. Other lineages of Trebouxia seem to be rarer, especially Trebouxia sp. OTU S04, which is sometimes present in P. pinnatifida. This study indicates the importance of extensive research including morphology, chemistry and analysis of molecular markers of both bionts in taxonomical studies of lichens.

Project description:BackgroundFactors promoting diversification in lichen symbioses remain largely unexplored. While Pleistocene events have been important for driving diversification and affecting distributions in many groups, recent estimates suggest that major radiations within some genera in the largest clade of macrolichens (Parmeliaceae, Ascomycota) vastly predate the Pleistocene. To better understand the temporal placement and sequence of diversification events in lichens, we estimated divergence times in a common lichen-forming fungal genus, Melanohalea, in the Northern Hemisphere. Divergence times were estimated using both concatenated gene tree and coalescent-based multilocus species tree approaches to assess the temporal context of major radiation events within Melanohalea. In order to complement our understanding of processes impacting genetic differentiation, we also evaluated the effects of Pleistocene glacial cycles on population demographics of distinct Melanohalea lineages, differing in reproductive strategies.ResultsWe found that divergence estimates, from both concatenated gene tree and coalescent-based multilocus species tree approaches, suggest that diversification within Melanohalea occurred predominantly during the Miocene and Pliocene, although estimated of divergence times differed by up to 8.3 million years between the two methods. These results indicate that, in some cases, taxonomically diagnostic characters may be maintained among divergent lineages for millions of years. In other cases, similar phenotypic characters among non-sister taxa, including reproductive strategies, suggest the potential for convergent evolution due to similar selective pressures among distinct lineages. Our analyses provide evidence of population expansions predating the last glacial maximum in the sampled lineages. These results suggest that Pleistocene glaciations were not inherently unfavorable or restrictive for some Melanohalea species, albeit with apparently different demographic histories between sexually and vegetatively reproducing lineages.ConclusionsOur results contribute to the understanding of how major changes during the Miocene and Pliocene have been important in promoting diversification within common lichen-forming fungi in the northern Hemisphere. Additionally, we provide evidence that glacial oscillations have influenced current population structure of broadly distributed lichenized fungal species throughout the Holarctic.

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

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