SSU RDNA PHYLOGENY OF CLADONIIFORM LICHENS

To examine phylogenetic relationships among the ''cladoniiform'' liche nized fungi, i.e., the families Cladoniaceae, Baeomycetaceae, Icmadoph ilaceae, Stereocaulaceae, and Siphulaceae, and to provide evidence for the anticipated independent origins of podetia and pseudopodetia, we conducted phylogenetic analyses of SSU (small subunit) rDNA sequences from 39 lichen-forming fungi. These fungi represent all of the major g rowth forms of lichen associations, fruticose (including ''cladoniifor m''), foliose, and crustose. Our analysis suggests that lichen-forming fungi with a ''cladoniiform'' morphology arose multiple times within the ascomycetes. Additionally, each of the other thallus growth forms, crustose, foliose, and fruticose, have originated multiple times. It also seems to be clear that neither all podetiate nor all pseudopodeti ate taxa form a monophyletic group. Therefore the term ''podetium'' sh ould be restricted to homologous structures that are most probably lim ited to the genera Cladonia, Cladina, Pycnothelia, and allies. The ''p seudopodetia'' of Stereocaulon (Stereocaulaceae) and Cladia (Cladiacea e) may represent different states of the same homologous character. Ou r phylogenetic hypothesis supports the monophyletic origin of the orde r Lecanorales sensu stricto, including representatives of five suborde rs Cladoniineae, Lecanorineae, Teloschistineae, Agyriineae and Peltige rineae, but excluding representatives of the suborders Acarosporineae (Acarospora schleicheri and Megaspora verrucosa), Pertusariineae (Pert usaria trachythallina), and Umbilicarineae. The suborder Cladoniineae and the family Cladoniaceae both appear to be polyphyletic assemblages .