Association of Varroa destructor females in multiply infested cells of the honeybee Apis mellifera

Abstract

The genetic diversity of Varroa destructor (Anderson & Trueman) is limited outside its natural range due to population bottlenecks and its propensity to inbreed. In light of the arms race between V. destructor and its honeybee (Apis mellifera L.) host, any mechanism enhancing population admixture of the mite may be favored. One way that admixture can occur is when two genetically dissimilar mites coinvade a brood cell, with the progeny of the foundresses admixing. We determined the relatedness of 393 pairs of V. destructor foundresses, each pair collected from a single bee brood cell (n = five colonies). We used six microsatellites to identify the genotypes of mites coinvading a cell and calculated the frequency of pairs with different or the same genotypes. We found no deviation from random coinvasion, but the frequency of cells infested by mites with different genotypes was high. This rate of recombination, coupled with a high transmission rate of mites, homogenized the allelic pool of mites within the apiary.

Population genetics of ectoparasitic mites suggest arms race with honeybee hosts

“…Low levels of genetic diversity have initially been reported from a large number of V. destructor populations infesting A. mellifera throughout the world, suggesting that strong bottlenecks have taken place after this parasite’s host switch and further dispersal of the infested colonies 25 . Yet, more recent studies have revealed that the diversity of V. destructor is not as limited as previously thought in populations of Europe 27 , the USA 31,32 and Asia 33,34 . The discrepancies between the earlier work on the varroa mite’s population genetics and the more recent investigations could be due to ( i ) the average low number of samples of the populations initially screened by Solignac et al .…”

“…Here, the lowest number of samples analysed in a group was well above this threshold (N = 41 in the S-current group). Additionally, populations of V. destructor are homogenous at the apiary level 31,32 . Therefore, clearly neither the difference in the number of colonies nor the difference in sample size used across the five groups had any significant impact on the genetic diversity estimates in our results.…”

Spatio‐temporal dynamics of Varroa destructor resistance to tau‐fluvalinate in Czechia, associated with L925V sodium channel point mutation

“…It is expected that the frequency of susceptible V. destructor mite genotypes would increase when the tau ‐fluvalinate selective pressure is discontinued . Recent studies on host specificity have switched from mitochondrial DNA markers to microsatellite DNA and discovered strong inbred lines of V. destructor mites . The life cycle of V. destructor results in extreme inbreeding because of sibling mating in host brood cells .…”

“…The life cycle of V. destructor results in extreme inbreeding because of sibling mating in host brood cells . However, the drift of mites among colonies ensures the presence of a high number of different lineages in all colonies in an apiary . Owing to a high level of endogamy, V. destructor produces very few heterozygotes .…”

Three Decades of Selecting Honey Bees that Survive Infestations by the Parasitic Mite <em>Varroa destructor</em>: Outcomes, Limitations and Strategy

“…In V. destructor, recombination between genomes occurs among the offspring of different foundresses in multiply infested cells. The frequency of these cells increases with the infestation rates of colonies (Beaurepaire et al, 2017a); therefore, an increase in the genetic diversity of mites at the end of the beekeeping season occurs (Beaurepaire et al, 2017b) and creates variability, which could provide the parasite with advantages in the host-parasite arms race. The treatment or removal of highly infested colonies is, therefore, also useful in terms of preventing recombination events.…”