In this study we examined photobiont identity, diversity and selectivity in the genus Bryoria. We focused on B. fremontii and section Implexae in order to determine whether secondary chemistry is correlated with photobiont identity. DNA from two loci for photobionts and three loci for mycobionts was sequenced for both parsimony and Bayesian phylogenetic analyses. A comparison of photobiont and mycobiont phylogenies reveals that most Bryoria species associate exclusively with lineages of the Trebouxia simplex group; only B. smithii was associated with a different photobiont. We conclude that most Bryoria species included in our study are highly selective in their choice of algal partners and that the presence/concentration of different secondary compounds does not correlate with photobiont identity either in section Implexae or in B. fremontii.

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 clade of T. simplex was detected which also occurs in Polish mountains, south Sweden and Austria. A further clade 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.