Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2004
Publication Date: 3/1/2005
Citation: Rehner, S.A., Buckley, E.P. 2005. Cryptic diversification in beauveria bassiana inferred from nuclear its and ef1- alpha phylogenies. Mycologia. 97:84-98
Interpretive Summary: Beauveria is a soil-inhabiting fungal parasite of insects used for biological control of agricultural insect pests. Identifying species of Beauveria is difficult because these fungi are structurally simple and appear very similar to one another. As an alternative, we have created a database of gene sequences for species identification and for determining their evolutionary relationships. The genetic data show that there are many more species of Beauveria than previously believed. Evolutionary analyses help explain how these fungi have evolved with their insect hosts. The sequence database is useful to scientists performing basic research, to industry for genotyping proprietary strains and monitoring for quality control, and government agencies responsible for regulating the introduction and environmental release of these fungi.
Technical Abstract: Beauveria bassiana is a globally distributed, soil-borne entomopathogenic hyphomycete of practical interest as a biological control agent of pest insects. Species recognition in Beauveria is difficult due to a lack of taxonomically informative morphological characters, which complicates both the routine identification of environmental isolates and the assessment of species diversity in this genus. A gene-genealogical approach was used to investigate molecular phylogenetic diversity of B. bassiana and related species based on analysis of ITS and EF1alpha sequences for 77 exemplar strains isolated from diverse geographic origins, habitats and insect hosts. The contribution of ITS to phylogenetic resolution in Beauveria was nominal in comparison to EF1alpha, which was highly informative. Phylogenetic trees were inferred using both maximum parsimony and Bayesian likelihood methods. Six major clades, dubbed A-E, were resolved in the EF1alpha and combined gene phylogenies. The high level of internal cladistic structure that characterized clades A-D is suggestive that cryptic diversification has occurred in these groups. Strains in clades A and C infect a broad range of insect hosts and the available evidence suggests that these clades are not host specific. The correspondence between genetically derived groups and geography in Beauveria is consistent with a mode of allopatric divergence. Two collections of Cordyceps cf. scarabaeicola, from Nepal and Korean, were intimately associated with Beauveria s.l.. These results establish a baseline phylogenetic framework for further taxonomic, phylogenetic and comparative biological investigations of Beauveria and their related sexual counterparts, Cordyceps.