Lichens have evolved independently between nine and twelve times since. Today, one in five of all known fungal species form lichens, or “lichenize.” Some fungi (such as Penicillium molds) used to lichenize but don’t anymore; they have de-lichenized. Some fungi have switched to different types of photosynthetic partner—or re-lichenized—over the course of their evolutionary histories. For some fungi, lichenization remains a lifestyle choice; they can live as lichens or not depending on their circumstances.
