Paleogeography, Chemistry and Taxonomy of the Lichenized Ascomycetes Dimelaena and Thamnolia

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Abstract
World distribution of the species of Dimelaena and Thamnolia, and chemical variants, are considered in relation to current concepts of continental drift. It is concluded that both genera date from the Permian-Triassic. Paleogeographies of species and chemotypes are presented which are consistent with the established sequence of continental movements. Long-distance dispersal has probably occurred in both species of Thamnolia. Seven chemotypes of Dimelaena oreina are now known and are interpreted as belonging to 3 races with differing paleogeographies. The races correspond to the fumarprotocetraric acid, gyrophoric acid-deficient chemotypes and the stictic/norstictic chemotypes. They were not given taxonomic recognition because the acid deficient chemotype may not be genetically homogenous, possibly incorporating acid deficient phases of the 2 other races in addition to the acid deficient phase of the gyrophoric acid chemotype. The fumarprotocetraric and gyrophoric acid chemotype incorporates substances of 2 races and does not occur outside the area of sympatry. This chemotype is best regarded as either a cross or a mycobiont chimera of its constituent races.

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