Molecular Innovations in Lichen Systematics: The Use of Ribosomal and Intron Nucleotide Sequences in the Cladonia chlorophaea Complex

In the mycobiont of the Cladonia chlorophaea complex, length variation in the ribo- somal DNA is explained, in part, by the variable occurrence of multiple group I introns that may have been mobile during the evolution of this group. These potentially mobile introns can serve as a model for examining the variation detected in the ribosomal DNA from other lichens and, perhaps, as a model for examining variation in other genes, genotypes, and phenotypes. Because group I introns have been found also in the ribosomal DNA of some green algae, lichens may provide a good system to search for evidence of intron transfer between distantly related organisms. Not only can molecular systematics change the way we look at lichens, but lichens may change the way we look at molecular evolution.