Phylogenetic relationships and evolution of photobiont associations in the Lobariaceae (Peltigerales, Lecanoromycetes, Ascomycota)

Phylogenetic relationships of the family Lobariaceae (Lecanoromycetes, Ascomycota) were reconstructed using direct optimization of nuclear ITS and LSU, and mitochondrial SSU rDNA sequences. Delimitations of the genera currently included in the family were investigated. Relationships of austral temperate taxa occurring in New Zealand, Australia and southern South America were studied in detail. Finally, we studied the evolution of the symbiotic associations found in the family which proved to be monophyletic. Sticta, with the exception of S. oroborealis, but including Dendriscocaulon dendroides, was found to be monophyletic while the genera Lobaria and Pseudocyphellaria turned out to be non-monophyletic. The status of Lobariella, and Lobarina as independent genera was not supported. Relationships of southern temperate Sticta species indicate a common Gondwanan ancestor. In rest of the family, species from the austral temperate zone group together with more widespread species. The ancestor of the Lobariaceae was associated with cyanobacteria. Green algal photobionts have subsequently been acquired repeatedly, but also repeatedly lost within the family. The acquisition of green algae has not resulted in a complete loss of the cyanobacterial photobiont. The cyanobacterial symbioses therefore seem to be more stable than those with green algae.