The paradox of tolerance: Being intolerant of Varroa tolerant bees is necessary for Varroa resistance evolution

Movement of Varroa between honeybee colonies has long been posited (and more recently, evidenced!) as a driver of apiary -level epidemiology, colony losses, and hurdle to precision treatment as part of IPM frameworks. Here, we use a newly-derived Varroa x Brood x Adult honey bee population model to investigate how honeybee phenotype (susceptible, tolerant, resistant) alters population dynamics and the epidemiology of apiaries, especially in "mixed-phenotype" contexts within apiaries. Our modelling results clearly point to two emergent phenomena: that higher rates movement of Varroa between colonies (i.e. higher rates of drift or robbing) reduce the parameter space that permits for resistant bees to passively evolve (e.g. without active intervention) in the presence of susceptible bees; and that it is impossible for resistant bees to evolve through standard "survivorship only" natural selection in an apiary that also houses tolerant bees. Beyond the obvious importance of this for how beekeepers go about managing honeybee stock evolution, this generalized finding of tolerant phenotypes sabotaging positive selection for rare resistant phenotypes is novel to the host-parasite evolutionary ecology field.