The potential of mitochondrial DNA for establishing phylogeny and stabilising generic concepts in the parmelioid lichens

A satisfactory resolution of the current instability of generic concepts in the parmelioid lichens, and particularly Parmelia s.l., has not so far eme rged from molecular studies. The rDNA ITS sequence has proven too variable and the rDNA SSU too conserved to provide satisfactory discrimination aroun d the family and generic levels in Parmeliaceae s.l. Studies of 31 new sequ ences of species belonging to 30 genera in the family (including the type s pecies of 21) are reported here. These demonstrate that the mitochondrial D NA (mtDNA) SSU region has the potential to play a major role in establishin g the phylogeny and stabilising generic concepts in some of the world's mos t conspicuous lichens. Some clades identified appear to correlate with diff erences in cell wall carbohydrates, epicortical, conidial, and other featur es. The emerging groupings now need to be further tested by the inclusion o f sequences from additional genera and species. Nomenclatural changes shoul d not be made until further work has been carried out.