Trentepohliales are a group of both free-living and lichenized algae, essentially found in tropical regions. Recently the abundance of lichens with a trentepohlioid photobiont has been increasing in temperate habitats, probably because of global warming. A detailed study of the diversity of lichenized Trentepohliales was performed in three forests of north-western Europe. Additional samples of trentepohlioid lichens from other regions in the world were also sequenced. Phylogenetic analyses using the rbcL locus were performed and association between phylogenetic distances of photobionts and ecological factors (climate, geographic location, mycobiont taxonomy and substratum) were tested by variation partitioning and phylogenetic signal analyses. Results showed that the Trentepohliales diversity in extratropical regions was underestimated. The phylogenetic patterns showed selectivity of some photobionts in one fungal partner choice and vice-versa, while others were linked with several haplotypes. Photobionts seemed to be less selective than mycobionts. The main factors influencing lichenized algal community were climate and fungal taxa. Photobiont switching between mycobiont species as well as between free living and lichenized lifestyles appeared to drive the evolution of Trentepohliales and might explain the high cryptic diversity observed.