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Varroa destructor, an ectoparasite of Apis cerana (the Eastern honeybee), has attained global notoriety following the decimation caused by its host shift to Apis mellifera. Previous studies indicated that Varroa mites have geographic and host-specific mitochondrial haplotypes (mitotypes) in A. mellifera colonies, suggesting that only a few genetic strains (i.e., Korean and Japanese mitotypes) can effectively infest A. mellifera. However, growing evidence indicates that native mite populations of A. cerana can hybridize with the mites imported with A. mellifera colonies. This raises the possibility for continuous host shifts of Varroa mites and the consequential hybridizations among mites from different localities, leading to erasure of host specificity among mites of different mitotypes. We compared mitochondrial sequence data with restriction site-associated DNA sequencing (RAD-seq) to test the veracity of the patterns indicated by mitochondrial data and to clarify the genetic differentiation of Varroa mites in Vietnam and Taiwan. Our mitotype analyses replicate previous studies, indicating that only a few Varroa mite mitotype lineages parasitize A. mellifera. However, our RAD-seq data reveal little evidence of the genetic isolation as suggested by the mitotype analyses, instead indicating that hybridization is likely occurring among Varroa mites from multiple different hosts and localities. This indicates that the local mite community of A. cerana might contribute to the genetic pool of mites parasitizing A. mellifera. Our findings suggest that the Varroa mite control strategies and the risk estimation of international apicultural trade should be reassessed. [ABSTRACT FROM AUTHOR]

Hygienic behavior in honey bees reflects the social immunity against parasites and diseases and is considered one of the main factors of genetic resistance of the bee breeding program. Hygienic behavior refers to the uncapping and removal of diseased and dead larvae and pupae from sealed brood cells by the worker bees. Here, the hygienic behavior of Apis mellifera races was investigated in response to pin-killed assay and artificial Varroa mite-infested brood cells. Moreover, the reproduction behavior of Varroa mites was determined in various sizes of honey bee race comb cells. The results revealed that the percentage of uncapping and removal of dead broods were significantly higher in the Italian as compared to the Carniolan bee colonies (p < 0.05). Similarly, a significant difference was present in response to artificially infested brood cells with Varroa mites in Italian and Carniolan colonies over the day of inspection (p < 0.05). Overall, the width of cells of the two types of combs was significantly different. The smaller width of cells size combs reduces the Varroa mite reproduction behavior compared to larger cell size combs. More infestation of Varroa mite occurred in drone brood cells as compared to worker brood cells in both old and new comb types. This study contributed to understand the hygienic behavior of A. mellifera races in preparation for selecting and developing hygienic lines of bees given the important contribution of hygienic behavior to honey bee health. [ABSTRACT FROM AUTHOR]