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Title: Phylogenetic and genetic diversity of the fungal entomopathogen Beauveria in adjacent agricultural and semi-natural habitats

item Rehner, Stephen

Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2008
Publication Date: 1/30/2009
Citation: Meyling, N., Lubeck, M., Eilenberg, J., Rehner, S.A. 2009. Phylogenetic and genetic diversity of the fungal entomopathogen Beauveria in adjacent agricultural and semi-natural habitats. Molecular Ecology. 18:1282-1293.

Interpretive Summary: Beauveria is a soil-inhabiting fungus that kills a wide range of agriculturally important insects and thus is a safe non-chemical alternative to controlling insect pests. The use of these fungi to control insects is limited by lack of knowledge of their function and ecology in agricultural systems. In this study the presence and distribution of Beauveria is compared in organic agricultural versus semi-natural hedgerow habitats. A total of seven Beauveria species were isolated from soils, leaf surfaces and insects. A single species was common in both the tilled and hedgerow habitats. The hedgerow harbored six species not present in the tilled soils. Agricultural ecosystems appear to select for fewer Beauveria species compared to less disturbed habitats. These results will be useful to scientists working to develop fungi as a biological control agent for agricultural insect pests.

Technical Abstract: Although intensively investigated for the biological control of insect pests, little is known about the ecology of the fungal entomopathogenic genus Beauveria in natural or agricultural habitats. In this study we used molecular phylogenetic and multilocus genotyping approaches to infer species diversity, genetic diversity and reproductive mode of Beauveria within a single agro-ecosystem and bordering hedgerow in Denmark. Isolates were sampled from a cultivated field and hedgerow soils, from insects harbouring latent fungal infections, and from the phylloplanes of three plant species common in the hedgerow flora. A two-locus nuclear phylogeny of this local Beauveria assemblage resolved seven distinct terminal lineages, including 1) five lineages within Beauveria bassiana sensu stricto, 2) Clade C, a taxonomically uncharacterized clade that is morphologically indistinguishable but phylogenetically distant from B. bassiana s.s., and 3) Beauveria brongniartii. All Beauveria species lineages detected were present in the hedgerow habitat but only the single B. bassiana s.s. phylogenetic species Eu_1 was isolated from the tilled soils. Mating type PCR assays demonstrated that four of the five B. bassiana s.s. phylogenetic species were fixed for a single mating type. This suggests that the predominant asexual mode characteristic of these fungi may in many cases be due to fixation for single mating types in local populations. By contrast, two mating types were detected in Eu_1, indicating that this population possesses the potential for sexual recombination. However, the 32:1 skew in MAT1:MAT2 mating type suggests that factors other than mating type may also play a role in the bias for mitotic reproduction by these fungi. Multilocus microsatellite genotyping revealed polymorphism in all five phylogenetic species of B. bassiana s.s., however, all species include two or more multilocus genotypes that are plausibly clonally related.