Phylogeny of the genus Arthrobotrys and allied nematode-trapping fungi based on rDNA sequences

Abstract

Ribosomal DNA of 29 nematode-trapping fungi in the genera Arthrobotrys, Dactylella, Duddingtonia, Geniculifera, Monacrosporium, Nematoctonus, and 5 nonpredacious, allied fungi in the genera Orbilia, Trichothecium, Dactylaria, and Arthrobotrys was amplified by polymerase chain reaction 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. Clamped Nematoctonus robustus, having a Hohenbuehelia basidiomycetous teleomorph, was phylogenetically distant and the predacious habit was gained through convergent evolution. Nonpredacious Arthrobotrys, Dactylaria, and Trichothecium species, despite having morphologically similar conidiogenous cells and conidia, actually were grouped in a genetically distant region of the tree. Analysis of the more variable internal transcribed spacer, ITS1 and ITS2, revealed that the 28 nematode-trapping fungi were separated into 4 clades, each with a unique trapping device. Phylogenetic analysis of rDNA of trapping fungi in this study indicated 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-Dactylella-Monacrosporium complex be revised to provide a natural classification system.

Key Words:

• molecular evolution
• nematophagous fungi
• systematics
• taxonomy