The Use of Metabolic Data in Lichenology at the Species and Subspecific Levels

The different views on the taxonomic use of chemical characters in lichenology are reviewed using the opposing opinions of W. L. Culberson and Rogers and the somewhat intermediate position of Hawksworth as examples. The differing significance of secondary metabolites is illustrated with two examples in the genus Lecanora. In L. campestris and similar species, the chemistry has been useful to differentiate morphologically similar species, which subsequently were found to differ in minute anatomical differences as well. However, in L. caesiorubella, a remarkable chemical variation can be observed that is not correlated with other differences and is thus interpreted as intraspecific variation. An a posteriori valuation of the taxonomic significance of metabolic data is preferred.