Electron Microscope Studies of Lichen Reproductive Structures in Physcia Aipolia

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 the lecanoralean lichen families Caliciaceae and Physciaceae form a well-supported monophyletic group within the order Lecanorales (Ascomycotina). Support for this relationship is present from anatomical data, in particular data from spore ontogeny, where close similarities between the pattern of development of spore surface structures in the two families are pointed out. The Caliciaceae-Physciaceae group is characterized by having thick-walled, pigmented spores, often with a distinctive ornamentation which is usually formed either from strongly melanized parts of the perispore, separated by nonmelanized, 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 jackknifing, but cannot be rejected with the present data. There is no support for the suggested order Teloschistales. A brief discussion of the evolution of the prototunicate ascus in the Lecanorales is given. New SSU rDNA sequences were produced from Buellia disciformis (Fr.) Mudd. and Physcia aipolia (Humb.) Fürnr. (Physciaceae), Cladonia sulphurina (Michx.) Fr. (Cladoniaceae), Cyphelium tigillare (Ach.) Ach. (Caliciaceae), and Caloplaca flavorubescens (Huds.) J.R. Laundon and Xanthoria parietina (L.) Th.Fr. (Teloschistaceae).Key words: 18S, fungi, lichens, molecular phylogeny, ribosomal DNA.