Virulence traits within a community of the fungal entomopathogen Beauveria: Associations with abundance and distribution

Entomopathogenic fungi are widespread in terrestrial ecosystems and can be used as models for studying host-pathogen interactions. However, the associations between fungal virulence and ecosystem abundance, and the importance of virulence for ecological fitness are poorly understood. To study these associations, we investigated five selected strains from a natural community of the entomopathogenic genus Beauveria spp. representing different phylogenetic clades with distinct abundance and distribution patterns within an agricultural field and its neighboring hedgerow. We measured pathogen fitness traits related to virulence in a naïve host, the beetle Tenebrio molitor. We found that the two strains belonging to the most abundant Beauveria bassiana clade, which was the only clade represented in the agricultural field, exhibited the highest relative virulence in terms of host mortality, transmission probability, in vitro growth rate and germination speed. In addition, gene expression of specific virulence factors was higher compared to the strain belonging to the second most abundant B. bassiana clade. The study highlights the relevance of fungal virulence traits and adaptations to explain abundance patterns within natural communities of entomopathogenic fungi.