Trentepohliales are a group of essentially tropical algae, both free-living and lichenized. Lichens associated with trentepohlioid lichens mainly belong to Arthoniales, Ostropales and Pyrenulales orders. Recently there has been evidence of increasing abundance of trentepohlioid lichens in temperate habitats, probably because of global warming. In order to better assess the diversity and distribution of lichenized Trentepohliales and the factors driving their abundance and diversity, a detailed phylogenetic study was performed in three forests of western Europe in 2020. Additional samples of trentepohlioid lichens from other regions in the world were also sequenced. A phylogenetic analysis using the rbcL locus was performed and association between phylogenetic distances among photobionts and ecological (climate, mycobiont taxonomy and substratum) and geographic factors were tested by variation partitioning and phylogenetic signal analyses. The main factors influencing lichenized algal communities were climate and fungal taxa, suggesting that global warming might be the main factor responsible for the rise of Trentepohliales in temperate regions. Results also demonstrated that the diversity of trentepohlioid algae in extratropical regions was underestimated. The phylogenetic patterns showed selectivity of some lichens, with algal association restricted to one single algal partner and vice-versa, while others were linked with several haplotypes. Photobionts seemed to be less selective than mycobionts. 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.