Data from: The hitchhiker's guide to Europe: the infection dynamics of an ongoing Wolbachia invasion and mitochondrial selective sweep in Rhagoletis cerasi

Wolbachia is a maternally inherited and ubiquitous endosymbiont of
insects. It can hijack host reproduction by manipulations such as
cytoplasmic incompatibility (CI) to enhance vertical transmission.
Horizontal transmission of Wolbachia can also result in the colonization
of new mitochondrial lineages. In this study, we present a 15-year-long
survey of Wolbachia in the cherry fruit fly Rhagoletis cerasi across
Europe and the spatiotemporal distribution of two prevalent strains, wCer1
and wCer2, and associated mitochondrial haplotypes in Germany. Across most
of Europe, populations consisted of either 100% singly (wCer1) infected
individuals with haplotype HT1, or 100% doubly (wCer1&2) infected
individuals with haplotype HT2, differentiated only by a single nucleotide
polymorphism. In central Germany, singly infected populations were
surrounded by transitional populations, consisting of both singly and
doubly infected individuals, sandwiched between populations fixed for
wCer1&2. Populations with fixed infection status showed perfect
association of infection and mitochondria, suggesting a recent CI-driven
selective sweep of wCer2 linked with HT2. Spatial analysis revealed a
range expansion for wCer2 and a large transition zone in which wCer2
splashes appeared to coalesce into doubly infected populations.
Unexpectedly, the transition zone contained a large proportion (22%) of
wCer1&2 individuals with HT1, suggesting frequent intraspecific
horizontal transmission. However, this horizontal transmission did not
break the strict association between infection types and haplotypes in
populations outside the transition zone, suggesting that this horizontally
acquired Wolbachia infection may be transient. Our study provides new
insights into the rarely studied Wolbachia invasion dynamics in field
populations.