Nearly one-fourth of the lichen-forming fungi associate with trentepohlialean algae, yet their genetic diversity remains unknown. Recent work focusing on free-living trentepohlialean algae has provided a phylogenetic context within which questions regarding the lichenization of these algae can be asked. Here, we concentrated our sampling on trentepohlialean algae from lichens producing a diversity of growth forms (fruticose and crustose) over a broad geographic substratum, ecological, and phylogenetic range. We have demonstrated that there is no evidence for a single clade of strictly lichenized algae; rather, a wide range demonstrated the ability to associate with lichenized fungi. Variation was also observed among trentepohlialean algae in lichens from a single geographic area and tree, suggesting that fungi in close proximity can associate with different trentepohlialean algae, consistent with the findings of trebouxiophycean algae and cyanobacteria.