Adaptive population structure shifts in invasive parasitic mites, Varroa destructor

Abstract

Comparative studies of genetic diversity and population structure can shed light on the ecological and evolutionary factors governing host–parasite interactions. Even though invasive parasites are considered of major biological importance, little is known about their adaptative potential when infesting the new hosts. Here, the genetic diversification of Varroa destructor , a novel parasite of Apis mellifera originating from Asia, was investigated using population genetics to determine how the genetic structure of the parasite changed in distinct European populations of its new host. To do so, mites infesting two categories of hosts in four European regions were compared: (a) adapted hosts surviving through means of natural selection, thereby expected to impose strong selective pressure on the mites, and (b) treated host populations, surviving mite infestations because acaricides are applied, therefore characterized by a relaxed selection imposed by the host on the mites. Significant genetic divergence was found across regions, partially reflecting the invasion pattern of V. destructor throughout Europe and indicating local adaptation of the mite to the host populations. Additionally, varying degrees of genotypic changes were found between mites from adapted and treated colonies. Altogether, these results indicate that V. destructor managed to overcome the genetic bottlenecks following its introduction in Europe and that host‐mediated selection fostered changes in the genetic structure of this mite at diverse geographic scales. These findings highlight the potential of parasites to adapt to their local host populations and confirm that adaptations developed within coevolutionary dynamics are a major determinant of population genetic changes.

Migratory beekeeping facilitates genetic admixture in populations of the honeybee parasite Varroa destructor

“…Given our dataset includes a larger geographic range and larger coverage of ecological and management diversity, we expect it better represents actual Varroa mite diversity across the country. Our observations were also slightly lower than a study across the mite's native range in Asia (Dietemann et al, 2019) and one across introduced populations in Europe (Moro et al, 2021), but both are within the same order of magnitude. While these three studies are based on satellite repeat regions, we believe our results are roughly comparable, indicating less diversity in the United States compared to Europe and Southeast Asia.…”

Dynamics in vertical transmission of viruses in naturally selected and traditionally managed honey bee colonies across Europe

“…Therefore, it remains uncertain if the higher infection frequencies are a result of increased virus circulation in the naturally surviving populations. The high variability between both groups in each country can be caused by previously mentioned factors affecting virus abundance, the time since colonies were left untreated [37,38], or the degree of genetic divergence between TMC and NSC within a country [62,74,102]. Honey bee queens accumulate viral infections and infection loads during queen rearing [109,110], during mating flights [58,60,111] or as they get older [60,64,79] despite increased immune responses [112].…”

“…Therefore, it remains uncertain if the higher infection frequencies are a result of increased virus circulation in the naturally surviving populations. The high variability between both groups in each country can be caused by previously mentioned factors affecting virus abundance, the time since colonies were left untreated [37,38], or the degree of genetic divergence between TMC and NSC within a country [62,74,102].…”

“…Dynamics in the presence and abundance of honey bee viruses show strong seasonal and geographic variation [34][35][36]. This variation is driven by local adaptation of both virus, host and vector species as well as by the specific characteristics of each virus [37][38][39][40][41]. Together they form a geographic mosaic of coevolution [42].…”

Varroa destructor from the Laboratory to the Field: Control, Biocontrol and IPM Perspectives—A Review

“…The population dynamics, structure and genetics of the mite are crucial to understand the spreading process as well as their adaptations and resistances [52,53]. Varroa destructor mating biology leads to intense inbreeding with no exchange among lineages in the population while a single foundress invades a brood cell.…”