PHYLOGENY OF THE GENUS ARTHROBOTYRS AND ALLIED NEMATODE-TRAPPING FUNGI BASED ON RDNA SEQUENCES

Ribosomal DNA of 29 nematode-trapping fungi in the genera Arthrobotrys , Dactylella, Duddingtonia, Geniculifera, Monamosporium, Nematoctonus, and 5 nonpredacious, allied fungi in the genera Orbilia, Trichotheciu m, Dactylaria, and Arthrobotrys was amplified by polymerase chain reac tion and sequenced using universal primers. Phylogenetic analysis of 5 .8S rDNA using parsimony indicated that 28 clampless nematode-trapping fungi were monophyletic and have evolved from a common ancestor. Clam ped Nematoctonus robustus, having a Hohenbuehelia basidiomycetous tele omorph, was phylogenetically distant and the predacious habit was gain ed through convergent evolution. Nonpredacious Arthrobotrys, Dactylari a, and Trichothecium species, despite having morphologically similar c onidiogenous cells and conidia, actually were grouped in a genetically distant region of the tree. Analysis of the more variable internal tr anscribed spacer, ITS1 and ITS2, revealed that the 28 nematode-trappin g fungi were separated into 4 clades, each with a unique trapping devi ce. Phylogenetic analysis of rDNA of trapping fungi in this study indi cated that trapping organs may reflect evolutionary relationship, and appear more significant than conidiogenous cells and conidia for genus and species delimitation. We suggest that the circumscription of the Arthrobotrys-Dactyella-Monacrosporium complex be revised to provide a natural classification system.