 "Parmelia" and "Usnea" are the best chemically characterized genera, while the species "Cetraria islandica" and "Evernia prunastri" have attracted considerable research attention for their bioactive compounds.The main photobiont genus that associates with Parmeliaceae species is the Chlorophyte "Trebouxia".In particular, the species "Trebouxia jamesii" appears to be especially prominent.