Multiple host shifts by the emerging honeybee parasite, Varroa jacobsoni

Abstract

Host shifts are a key mechanism of parasite evolution and responsible for the emergence of many economically important pathogens. Varroa destructor has been a major factor in global honeybee (Apis mellifera) declines since shifting hosts from the Asian honeybee (Apis cerana) > 50 years ago. Until recently, only two haplotypes of V. destructor (Korea and Japan) had successfully host shifted to A. mellifera. In 2008, the sister species V. jacobsoni was found for the first time parasitizing A. mellifera in Papua New Guinea (PNG). This recent host shift presents a serious threat to world apiculture but also provides the opportunity to examine host shifting in this system. We used 12 microsatellites to compare genetic variation of V. jacobsoni on A. mellifera in PNG with mites on A. cerana in both PNG and surrounding regions. We identified two distinct lineages of V. jacobsoni reproducing on A. mellifera in PNG. Our analysis indicated independent host shift events have occurred through small numbers of mites shifting from local A. cerana populations. Additional lineages were found in the neighbouring Papua and Solomon Islands that had partially host shifted to A. mellifera, that is producing immature offspring on drone brood only. These mites were likely in transition to full colonization of A. mellifera. Significant population structure between mites on the different hosts suggested host shifted V. jacobsoni populations may not still reproduce on A. cerana, although limited gene flow may exist. Our studies provide further insight into parasite host shift evolution and help characterize this new Varroa mite threat to A. mellifera worldwide.

Varroa destructor changes its cuticular hydrocarbons to mimic new hosts

“…Our data here suggest that, at least for mites from Ac, some active processes might be involved because they mimicked their hosts better. Regardless, this ability may have played a critical role in Vd's ability to shift host species [17]. Our results give a clear illustration of an arms race between a parasite and its host based on chemical mimicry and its detection.…”

Honey Bees and Colony Collapse Disorder: A Pluralistic Reframing

“…There is a need to invest in diverse kinds of research and to expect that future ecological surprises are inevitable. The possibility of the emergence of a new species of invasive varroa mite (Roberts et al 2015), changes in honey bee genetics over time and space (Desai and Currie 2015;Locke et al 2012), and the vagaries of economic and political instability (Moritz and Erler 2016) highlight the importance of maintaining an appreciation of the novelty and possibilities of the future.…”

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

“…Given recent findings showing low levels of genetic differentiation among Varroa populations over large scales (Beaurepaire et al, 2015;Roberts et al, 2015;Dynes et al, 2016), we chose to investigate a finite number of colonies from a single apiary. This way, we were able to analyze a large number of mite pairs per colony and managed to appreciate for the first time the true extent of intra-colonial genetic diversity in V. destructor.…”