Epilichen

Epilichen is a small genus of lichen-forming fungi in the family Rhizocarpaceae. These parasitic lichens live on other lichens, beginning as thin, crust-like patches that may break into small islands or scales, and in some cases produce no visible body at all except for their reproductive structures. They reproduce through black, disc-shaped fruiting bodies that contain distinctive brown spores with a "doughnut ring" appearance, and can eventually take over the space occupied by their host lichen once it dies.