Ramalina sarahae is described as new to science and considered to be closely related to the widespread R. lacera. It has a cortex without chondroid strands but differs from R. lacera in having a densely caespitose thallus of thin branches with only pseudocyphellae. The species is considered to be naturally rare, occurring in a small area of San Miguel Island in southern California, and on San Nicolas Island. Currently eight species of Ramalina are known from the Channel Islands.