Co-evolution is a major driving force shaping the outcome of host-parasite interactions over
time. After host shifts, the lack of co-evolution can have a drastic impact on novel host populations.
Nevertheless, it is known that Western honey bee (Apis mellifera) populations can cope with hostshifted
ectoparasitic mites (Varroa destructor) by means of natural selection. However, adaptive
phenotypic traits of the parasites and temporal variations in host resistance behavior are poorly
understood. Here, we show that mites made adaptive shifts in reproductive strategy when associated
with resistant hosts and that host resistance traits can change over time. In a fully-crossed field
experiment, worker brood cells of local adapted and non-adapted (control) A. mellifera host colonies
were infested with mites originating from both types of host colonies. Then, mite reproduction
as well as recapping of cells and removal of infested brood (i.e., Varroa Sensitive Hygiene, VSH)
by host workers were investigated and compared to data from the same groups of host colonies
three years earlier. The data suggest adaptive shifts in mite reproductive strategies, because mites
from adapted hosts have higher probabilities of reproduction, but lower fecundity, when infesting
their associated hosts than mites in treated colonies. The results confirm that adapted hosts can
reduce mite reproductive success. However, neither recapping of cells nor VSH were significantly
expressed, even though the latter was significantly expressed in this adapted population three years
earlier. This suggests temporal variation in the expression of adaptive host traits. It also appears as if
mechanisms not investigated here were responsible for the reduced mite reproduction in the adapted
hosts. In conclusion, a holistic view including mite adaptations and studies of the same parasite/host
populations over time appears overdue to finally understand the mechanisms enabling survival of
V. destructor-infested honey bee host colonies.