Abstract
Wolbachia pipientis is an intracellular alphaproteobacterium that infects 40%–60% of insect species and is well known for host reproductive manipulations. Although Wolbachia are primarily maternally transmitted, evidence of horizontal transmission can be found in incongruent host–symbiont phylogenies and recent acquisitions of the same Wolbachia strain by distantly related species. Parasitoids and predator–prey interactions may indeed facilitate the transfer of Wolbachia between insect lineages, but it is likely that Wolbachia are acquired via introgression in many cases. Many hypotheses exist to explain Wolbachia prevalence and penetrance, such as nutritional supplementation, protection from parasites, protection from viruses, or direct reproductive parasitism. Using classical genetics, we show that Wolbachia increase recombination in infected lineages across two genomic intervals. This increase in recombination is titer-dependent as the wMelPop variant, which infects at higher load in Drosophila melanogaster, increases recombination 5% more than the wMel variant. In addition, we also show that Spiroplasma poulsonii, another bacterial intracellular symbiont of D. melanogaster, does not induce an increase in recombination. Our results suggest that Wolbachia infection specifically alters its host’s recombination landscape in a dose-dependent manner.
Highlights
Recombination, the exchange of genetic material during meiosis, is thought to be largely beneficial, as it increases the efficacy of natural selection [1,2]
Prior work has shown that Wolbachia infection is correlated with an increased frequency of recombination in natural populations [19,20]
We used the same set of isogenized flies, sampled from a wild-caught population in North Carolina, the Drosophila Genetic Reference Panel [24], to confirm prior observations of increased recombination in a Wolbachia-infected fly
Summary
Recombination, the exchange of genetic material during meiosis, is thought to be largely beneficial, as it increases the efficacy of natural selection [1,2]. Loci that are physically linked to each other can interfere with selection such that selection at one locus reduces the effective population size, and the efficacy of selection, at linked loci. This phenomenon, termed “Hill–Robertson interference,” means that positive or negative selection at one site can interfere with selection at another site. A large body of literature supports the assertion that recombination increases efficacy of selection and enhances adaptation in animals, as reviewed and studied in various Drosophila species [1,2,3]
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