Abstract
The ectoparasitic mite, Varroa destructor, is the most severe biotic threat to honeybees (Apis mellifera) globally, usually causing colony death within a few years without treatments. While it is known that a few A. mellifera populations survive mite infestations by means of natural selection, the possible role of mite adaptations remains unclear. To investigate potential changes in mite populations in response to host adaptations, the genetic structure of V. destructor in the mite-resistant A. mellifera population on Gotland, Sweden, was studied. Spatio-temporal genetic changes were assessed by comparing mites collected in these colonies, as well as from neighboring mite-susceptible colonies, in historic (2009) and current (2017/2018) samples. The results show significant changes in the genetic structure of the mite populations during the time frame of this study. These changes were more pronounced in the V. destructor population infesting the mite-resistant honeybee colonies than in the mite-susceptible colonies. These results suggest that V. destructor populations are reciprocating, in a coevolutionary arms race, to the selection pressure induced by their honeybee host. Our data reveal exciting new insights into host-parasite interactions between A. mellifera and its major parasite.
Highlights
Anthropogenic movement of species can threaten biodiversity, agriculture, ecosystem functioning and can facilitate the spread of harmful pathogens[1,2]
A total of 432 V. destructor adult females were genotyped at nine polymorphic microsatellite markers to study the temporal genetic structure of the mites in the mite-resistant colonies and local susceptible colonies from 2009 (“historic samples”) and 2017–18 (“current samples”) located on the island of Gotland, Sweden (Table 1)
The results of this study show that the genetic structure of V. destructor populations in the island of Gotland changed significantly between the time when our historic and current samples were collected, with differing degrees between the resistant and susceptible colonies
Summary
Anthropogenic movement of species can threaten biodiversity, agriculture, ecosystem functioning and can facilitate the spread of harmful pathogens[1,2]. The most dramatic consequence of the global spread of A. mellifera is the propagation of the invasive ectoparasitic mite, Varroa destructor This mite is inarguably the most severe threat to A. mellifera globally, practically exterminating wild colonies and severly affecting the management and profitability of beekeeping in the wake of its global spread during the 1980’s and 1990’s6. This research has highlighted that a wide range of individual or colony-level mechanisms are involved in their survival and that many of these traits are inheritable[13,14,15,16,17] One such well-studied isolated honeybee population on the island of Gotland, Sweden, has been living treatment-free for almost two decades[12]. This population was established in the late 1990’s as an isolated natural selection www.nature.com/scientificreports/
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