Complex sentence: The main photobiont that associates with Parmeliaceae species is the Chlorophyte genus "Trebouxia", and in particular the species "Trebouxia jamesii" appears to be especially prominent.
Split into simpler sentences: The main photobiont genus that associates with Parmeliaceae species is the Chlorophyte "Trebouxia". In particular the species "Trebouxia jamesii" appears to be especially prominent.