Reproduction of ectoparasitic mites in a coevolved system: Varroa spp.—Eastern honey bees, Apis cerana

Abstract

Parasite host shifts can impose a high selective pressure on novel hosts. Even though the coevolved systems can reveal fundamental aspects of host–parasite interactions, research often focuses on the new host–parasite relationships. This holds true for two ectoparasitic mite species, Varroa destructor and Varroa jacobsonii, which have shifted hosts from Eastern honey bees, Apis cerana, to Western honey bees, Apis mellifera, generating colony losses of these pollinators globally. Here, we study infestation rates and reproduction of V. destructor and V. jacobsonii haplotypes in 185 A. cerana colonies of six populations in China and Thailand to investigate how coevolution shaped these features. Reproductive success was mostly similar and low, indicating constraints imposed by hosts and/or mite physiology. Infestation rates varied between mite haplotypes, suggesting distinct local co‐evolutionary scenarios. The differences in infestation rates and reproductive output between haplotypes did not correlate with the virulence of the respective host‐shifted lineages suggesting distinct selection scenarios in novel and original host. The occasional worker brood infestation was significantly lower than that of drone brood, except for the V. destructor haplotype (Korea) from which the invasive lineage derived. Whether mites infesting and reproducing in atypical intraspecific hosts (i.e., workers and queens) actually predisposes for and may govern the impact of host shifts on novel hosts should be determined by identifying the underlying mechanisms. In general, the apparent gaps in our knowledge of this coevolved system need to be further addressed to foster the adequate protection of wild and managed honey bees from these mites globally.

Population genetics and host specificity of Varroa destructor mites infesting eastern and western honeybees

“…Since no A. cerana mites reproduced on the brood of A. mellifera, this points to the high ability of the host-shifted lineage to exploit its new host and to the low reproductive success of A. cerana mites in their original host. This is in line with reproductive abilities observed in natural infestations (Wang et al 2020) and might be due to as yet unknown resistance mechanisms.…”

“…Males could breed with daughters of foundress mites from different mitochondrial variants that invaded the same cells. Brood cells hosting several foundresses accounted for 16% of infestations by the K haplotype (Wang et al 2020), indicating that this is not a rare phenomenon. Such a high frequency could be due to the short period during which drones are produced in A. cerana and to the relatively small number of drones reared (Koeniger et al 2011).…”

A New Strain of Virus Discovered in China Specific to the Parasitic Mite Varroa destructor Poses a Potential Threat to Honey Bees

“…For A. mellifera colonies, the brood cells in the frames were opened and pupae were removed individually with a pair of tweezers to check for the presence of Varroa mites. Individual worker pupae with one Varroa mite parasitizing on them when the brood cell was opened were designated as ng low count of mites, while worker pupae with more than 10 Varroa mites, including the foundresses and the offspring, were defined as having high count of mites For A. cerana colonies, our sampling only focused on the adult workers as Varroa mites express strong avoidance to the A. cerana worker brood in the field and no Varroa -infested A. cerana worker brood was identified [ 61 , 62 ].…”

The first steps toward a global pandemic: Reconstructing the demographic history of parasite host switches in its native range

“…This variability has been recently demonstrated in the ability to reproduce in different lineages of V. destructor. Most lineages are unable to produce offspring onto the new honey bee host despite ideal conditions (Li et al, 2019) and those that can show variable fertility or fecundity levels depending on their own genetic background but also in response to their host (success only in haploid male drone bee in the original host) (Lin et al, 2021;Wang et al, 2020). This may have allowed some populations to switch, while others were unable to do so, in spite of available novel hosts.…”