Relationships of the insect-pathogenic order Entomophthorales (Zygomycota, Fungi) based on phylogenetic analyses of nuclear small subunit ribosomal DNA sequences (SSU rDNA).

We sequenced the nuclear small subunit of ribosomal DNA (SSU rDNA) from seven species within the insect-pathogenic order Entomophthorales. These sequences were aligned with other published SSU rDNA sequences and phylogenies were inferred using phenetic and cladistic methods. Based on three different phylogenetic methods the Entomophthorales (excluding Basidiobolus ranarum) is monophyletic; B. ranarum was more closely related to chytrids from Chytridiales and Neocallimasticales than to Entomophthorales, as was proposed by Nagahama et al. (Mycologia 87: 203-209, 1995). Nuclear characters (large nuclei containing conspicuous condensed chromatin and lack of a prominent nucleolus) were of predictive value for the monophyly of the family Entomophthoraceae. Conidial characters separate the Entomophthoraceae, which only includes obligate pathogens, into at least two lineages: one lineage with uninucleate conidia and another with multinucleate conidia. The two species of Conidiobolus studied were paraphyletic in our analyses and only distantly related to each other. This information may prove to be important in the use of these fungi as biocontrol agents.