Revisiting photobiont diversity in the lichen family Verrucariaceae (Ascomycota)

The Verrucariaceae (Ascomycota) is a family of mostly lichenized fungi with a unique diversity of algal symbionts, including some algae that are rarely or never associated with other lichens. The phylogenetic position of most of these algae has not yet been studied and, because morphology-based identifications can often be misleading, molecular data is necessary to revisit their identity and to explore patterns of association between fungal and algal partners. For this reason, the diversity of photobionts in this lichen family was investigated using molecular markers (rbcL and nuSSU) amplified from DNA extracts of lichen thalli and cultured isolates. Although a single algal genus, Diplosphaera (Trebouxiophyceae), was associated with 12 out of the 17 sampled genera of Verrucariaceae, representatives of eight other genera in five orders of the Chlorophyta and one genus in the Xanthophyceae also form lichen associations with members of the family. Fungal genera with simple crustose thalli (e.g. Hydropunctaria, Wahlenbergiella, Bagliettoa) use a high diversity and unusual selection of photobionts. In contrast, fungal genera with more complex thalli (e.g. Placidium, Dermatocarpon) tend to have lower photobiont diversity. Habitat requirements and phylogenetic histories are both partly reflected in the observed patterns of associations between lichenized fungi from the family Verrucariaceae and their photobionts.