Résumé
Emerging infectious diseases (EIDs) have contributed significantly to the
current biodiversity crisis, leading to widespread epidemics and
population loss. Owing to genetic variation in pathogen virulence, a
complete understanding of species decline requires the accurate
identification and characterization of EIDs. We explore this issue in the
Western honeybee, where increasing mortality of populations in the
Northern Hemisphere has caused major concern. Specifically, we investigate
the importance of genetic identity of the main suspect in mortality,
deformed wing virus (DWV), in driving honeybee loss. Using laboratory
experiments and a systematic field survey, we demonstrate that an emerging
DWV genotype (DWV-B) is more virulent than the established DWV genotype
(DWV-A) and is widespread in the landscape. Furthermore, we show in a
simple model that colonies infected with DWV-B collapse sooner than
colonies infected with DWV-A. We also identify potential for rapid DWV
evolution by revealing extensive genome-wide recombination in vivo. The
emergence of DWV-B in naive honeybee populations, including via
recombination with DWV-A, could be of significant ecological and economic
importance. Our findings emphasize that knowledge of pathogen genetic
identity and diversity is critical to understanding drivers of species
decline.