Population genetics of ectoparasitic mitesVarroaspp. in Eastern and Western honey bees

Abstract

Host shifts of parasites are often causing devastating effects in the new hosts. The Varroa genus is known for a lineage of Varroa destructor that shifted to the Western honey bee, Apis mellifera, with disastrous effects on wild populations and the beekeeping industry. Despite this, the biology of Varroa spp. remains poorly understood in its native distribution range, where it naturally parasitizes the Eastern honey bee, Apis cerana. Here, we combined mitochondrial and nuclear DNA analyses with the assessment of mite reproduction to determine the population structure and host specificity of V. destructor and Varroa jacobsonii in Thailand, where both hosts and several Varroa species and haplotypes are sympatric. Our data confirm previously described mite haplogroups, and show three novel haplotypes. Multiple infestations of single host colonies by both mite species and introgression of alleles between V. destructor and V. jacobsonii suggest that hybridization occurs between the two species. Our results indicate that host specificity and population genetic structure in the genus Varroa is more labile than previously thought. The ability of the host shifted V. destructor haplotype to spillback to A. cerana and to hybridize with V. jacobsonii could threaten honey bee populations of Asia and beyond.

Varroa destructor: how does it harm Apis mellifera honey bees and what can be done about it?

“…V. jacobsoni and V. destructor show very different evolutionary trajectories since their divergence [30]. Despite these differences, it seems that the two subspecies have a potential to hybridise [31]. If that is the case, hybridisation events could result in a new species of Varroa, possibly more detrimental, that would become a greater risk for honey bees.…”

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

“…and its original host, we screened A. cerana colonies in several regions in China and Thailand. In Thailand, A. cerana indica populations are infested by three V. jacobsonii haplotypes: North Thai infesting the Mainland host haplotype in the north of the country below 1,000 m altitude and Samui on Samui Island and Malay in the south, infesting the Sundaland host haplotype (Dietemann et al., 2019; Hepburn et al., 2001; Radloff et al., 2010; Rueppell et al., 2011; Warrit et al., 2006). In Eastern China, we screened A. cerana cerana populations infested by three V. destructor haplotypes: Japan in the north, Korea in the central region, and China in the south (Anderson & Trueman, 2000; Hepburn et al., 2001; Navajas et al., 2010; Radloff et al., 2010; Zhou et al., 2004; Z Lin, S Wang, P Neumann, G Chen, P Page, L Li, F Hu, H Zheng & V Dietemann, unpublished data).…”

<em>Varroa destructor</em>: A Complex Parasite, Crippling Honey bees Worldwide

“…The sympatry with A. mellifera offers additional spillover opportunities to other V. destructor lineages which cause additional threats if they spread out of Asia. Based on nuclear microsatellites, populations of V. jacobsoni and V. destructor may hybridize in A. cerana in Thailand, potentially indicating less host specificity and a more labile genetic population structure than previously thought [98].…”