Lichens flourish in a cleft between two trunks of a Bristlecone Pine. This wolf lichen (Letharia vulpina) grows like a multi-branched tuft or leafless mini-shrub. Lichens are composite organisms that arise from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. Lichens are not related to mosses or any other plants, but they do produce their own nutrition by photosynthesis. When they grow on plants, they do not live as parasites, but instead use the plant's surface as a substrate. Some lichens are considered to be among the oldest living things.