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.