The Melolontha melolontha pathogens Beauveria brongniartii and Beauveria pseudobassiana exhibit clonal genomic population structure in a European Alpine region
Beauveria brongniartii is a fungal pathogen of Melolontha melolontha, a European agricultural pest. Studies have focused on its use to control M. melolontha, however, the B. brongniartii population genomic structure remained unknown and particularly whether this structure is affected by its interaction with M. melolontha, timing of beetle swarming flights, geography or reproductive mode. Therefore, genome-wide SNP-polymorphisms were analyzed to infer the population genomics of Beauveria spp. isolated from M. melolontha adults in an Alpine region. Unexpectedly, only one-third of the isolates were B. brongniartii, whereas two-thirds were apportioned among cryptic taxa within B. pseudobassiana, this far unrecognized as M. melolontha pathogen. Given the prevalence of B. pseudobassiana, analyses were conducted on both species. No spatial or temporal genomic patterns were detected and no correlations were found with M. melolontha population structure, suggesting that fungal dispersal is independent of the beetle. Both species displayed clonal population structures, with B. brongniartii fixed for one mating type and B. pseudobassiana exhibiting both mating types, implying other factors than mating compatibility limiting sexual reproduction. We conclude that B. pseudobassiana has potential as control agent of M. melolontha adults and that Beauveria spp. genomic structure is mainly affected by asexual reproduction and long-distance dispersal.