Molecules and morphology in basidiomycete phylogeny

Abstract

To obtain an understanding of the relationships of the basidiomycetes, especially those with horizontally partitioned metabasidia, and of the evolution of structural characters, members of nine orders and an additional four genera of simple-septate fungi (Auriculariales sensu lato) were studied using cladistic analysis of light microscopic and ultrastructural characters. Comparisons were made with the nucleotide sequence from the 5′ end of the nuclear large subunit ribosomal RNA gene analyzed with several algorithms, including parsimony and maximum likelihood. Analyses of both morphological and molecular characters support similar phylogenetic conclusions, but polarization of some morphological characters was difficult without guidance from molecular data. The Uredinales are shown to be an advanced taxon arising from the simple-septate Auriculariales sensu lato, and some characters that they share with the ascomycetes result from convergent evolution. The simple-septate Auriculariales consists of more than one clade, and the related gasteroid Pachnocybe ferruginea possesses numerous derived light microscopic characters, including holobasidia. Key words: basidiomycetes, character evolution, cladistics, molecular evolution, phylogeny.