Rhizocarpon Geographicum, Map Lichen

Day 305: The complex of lichens which includes Rhizocarpon geographicum has been the subject of much debate. The "lumpers" of the scientific community lobby toward grouping the yellow-green "maps" into a smaller number of species based on distinct morphological differences (including some which require a microscope to determine) while the "splitters" lean toward separating them by the substances (chemicals) they contain. The latter method takes these colourful crustose species into a pit so deep that the average lichen enthusiast is inclined to throw up their hands in defeat, all hope of making a firm identification lost. How finely do we want to parse it? Is "splitting" necessary taxonomically, or is it something which should be a footnote to the lab analysis? In this case, I'm with the lumpers. Lichens are fascinating, so let's keep them approachable.

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!