Symbioses of lichen-forming fungi with Trentepohlialean algae

Trentepohliaceae are a distinct lineage of green algae frequently found in associations with lichen-forming fungi. We review the current knowledge about the phenotypic diversity of this group of algae which is complemented by currently available molecular data. These data do not confirm the traditional classification of the genera based on morphological inferences. We also present more specific data on the association patterns of epiphyllous representatives in tropical rain forests. Leaf-colonizing Porina species associate specifically with Phycopeltis algae of characteristic growth types. The analysis of partial rbcL sequences of the algal partners suggests that morphologically similar growth types are genetically highly diverse and may represent different species. The fungal species may switch among morphologically similar but genetically distinct algal lineages. This strategy could promote rapid colonization of the ephemeral leaf habitats. Bark-inhabiting lichens of temperate habitats seem to represent a few known morphological species of Trentepohliales, whereas tropical bark lineages seem to be more diverse. Even though Trentepohliales are pending a modern revision before precise figures can be given, their diversity appears to be much higher than thought before