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Molecular sequence data of the nuclear ITS region was used to investigate the diversity of photobionts in Polish samples of Flavocetraria nivalis. The samples came both from alpine habitats, as well as from lowland localities near the coast. All green algal symbionts were identified as members of the Trebouxia simplex aggregate. These were compared with those of additional samples from Flavocetraria nivalis collected in different parts of Europe and also with photobionts assigned to T. simplex from other lichens. Within the T. simplex aggregate, the Trebouxia ITS sequences from F. nivalis formed four clades. In the Polish lowland populations only a single dade of T. simplex was detected which also occurs in Polish mountains, south Sweden and Austria. A further dade of T. simplex is present in F. nivalis from Polish mountains and is also known from F. nivalis further north in Scandinavia and Greenland, as well as from other lichens in Sweden, the Austrian Alps, and Antarctica. [ABSTRACT FROM AUTHOR]

Anthropogenic disturbances can have strong impacts on lichen communities, as well as on individual species of lichenized fungi. Traditionally, lichen monitoring studies are based on the presence and abundance of fungal morphospecies. However, the photobionts, as well photobiont mycobiont interactions also contribute to the structure, composition, and resilience of lichen communities. Here we assess the genetic diversity and interaction patterns of algal and fungal partners in lichen communities along an anthropogenic disturbance gradient in Białowieża Forest (Poland). We sampled a total of 224 lichen thalli in a protected, a managed, and a disturbed area of the forest, and sequenced internal transcribed spacer (ITS) ribosomal DNA (rDNA) of both, fungal and algal partners. Sequence clustering using a 97% similarity threshold resulted in 46 fungal and 23 green algal operational taxonomic units (OTUs). Most of the recovered photobiont OTUs (14 out of 23) had no similar hit in the NCBI-BLAST search, suggesting that even in well studied regions, such as central Europe, a lot of photobiont diversity is yet undiscovered. If a mycobiont was present at more than one site, it was typically associated with the same photobiont OTU(s). Generalist species, i.e., taxa that associate with multiple symbiont partners, occurred in all three disturbance regimes, suggesting that such taxa have few limitations in colonizing or persisting in disturbed areas. Trebouxia jamesii associated with 53% of the fungal OTUs, and was generally the most common photobiont OTU in all areas, implying that lichens that associate with this symbiont are not limited by the availability of compatible photobionts in Central European forests, regardless of land use intensity. [ABSTRACT FROM AUTHOR]