The taxonomic pattern of algal association with lichen fungi may be explained by the fungal selection of algae that are available in the habitat, genetic compatibility between symbionts or mode of reproduction of the lichen. This study examined algal selection among species in the genera Evernia, Pseudevernia and Imshaugia of the Parmeliaceae using nucleotide sequences of the algal Internal Transcribed Spacer (ITS) of the nuclear ribosomal DNA (rDNA), the algal actin gene, the 1512 group I intron and secondary RNA structures. The hypothesis of high selectivity within one species of Evernia examined, E. mesomorpha, was supported suggesting that E. mesomorpha exhibits high selectivity toward its photobiont, which is not shared with other species of lichenized fungi in the same habitat. The eight strongly supported ITS clades correspond with two newly described algal species broadly known as Trebouxia jamesii s.l. and one existing species, T. simplex. The possibility of lateral algal transfer is discussed with reference to algal availability and mode of reproduction of the lichen.