Rhizocarpon Geographicum, Map Lichen

Day 354: Hikers in the subalpine and alpine areas of Mount Rainier National Park may have passed by rocks populated by bright yellow-green patches of Rhizocarpon geographicum without ever giving them a second glance, or dismissing them from mind as "some kind of weird green stuff," perhaps not even knowing that they were observing a lichen, specifically a Map Lichen.

Rhizocarpon is a crustose lichen, which is to say it forms a crusty covering closely attached to the substrate material. This particular species is quite noticeable because of its striking hue, but other crustose lichens may be coloured to resemble the rocks on which they grow, i.e., grey with dot-like black or brown apothecia (fruiting bodies). Unlike the larger lichens, they are not a particularly valuable food source for animals, nor do they provide nesting material for birds, but they do make a vital contribution to the ecology in that they help break rock down into soil. It just goes to show that even that "weird green stuff" plays an important role in Nature!