Small subunit rDNA phylogeny shows the lichen families Caliciaceae and Physciaceae (Lecanorales, Ascomycotina) to form a monophyletic group

A phylogenetic analysis based on small subunit (SSU) rDNA sequences shows t he lecanoralean lichen families Caliciaceae and Physciaceae form a well-sup ported monophyletic group within the order Lecanorales (Ascomycotina). Supp ort for this relationship is present from anatomical data, in particular da ta from spore ontogeny, where close similarities between the pattern of dev elopment of spore surface structures in the two families are pointed out. T he Caliciaceae-Physciaceae group is characterized by having thick-walled, p igmented spores, often with a distinctive ornamentation which is usually fo rmed either from strongly melanized parts of the perispore, separated by no nmelanized, gelatinous parts that eventually dissolve, or by cracks in the perispore. The relationship to the Teloschistaceae, sometimes suggested as a possible sister-group to the Physciaceae, was not supported by jackknifin g, but cannot be rejected with the present data. There is no support for th e suggested order Teloschistales. A brief discussion of the evolution of th e prototunicate ascus in the Lecanorales is given. New SSU rDNA sequences w ere produced from Buellia disciformis (Fr.) Mudd. and Physcia aipolia (Humb .) Fnrnr. (Physciaceae), Cladonia sulphurina (Michx.) Fr. (Cladoniaceae), C yphelium tigillare (Ach.) Ach. (Caliciaceae), and Caloplaca flavorubescens (Huds.) J.R. Laundon and Xanthoria parietina (L.) Th.Fr. (Teloschistaceae).