Selective sweep of Wolbachia and parthenogenetic host genomes – the example of the weevil Eusomus ovulum

Abstract

Most parthenogenetic weevil species are postulated to have originated via hybridization, but Wolbachia has also been speculated to play a role via the induction of parthenogenesis. Here, we examine the molecular diversity of Wolbachia and parthenogenetic host genomes. The host species studied here, Eusomus ovulum, is known to be exclusively parthenogenetic and triploid. The E. ovulum populations that we examined had a low genetic diversity of mitochondrial (cytochrome oxidase I gene) and nuclear markers (internal transcribed spacer 2 and elongation factor 1-α gene), and they all were infected by only single bacteria strains (genotyped for five genes according to the multilocus sequence typing system). We found significant signs of linkage disequilibrium and a lack of recombination amongst all of the examined genomes (bacteria and host), which strongly indicates a selective sweep. The lack of heterozygosity in host nuclear genes, missing bisexual populations and selective sweep between the parthenogenetic host and bacteria genomes suggest that parthenogenesis in this species could have originated as a result of infection rather than hybridization. However, the finding that highly similar Wolbachia strains are also present in other parthenogenetic weevils from the same habitat suggests the opposite scenario: bacteria may have infected the already parthenogenetic lineage and taken advantage of the host's unisexual reproduction.

Global genetic diversity, lineage distribution, and Wolbachia infection of the alfalfa weevil Hypera postica (Coleoptera: Curculionidae)

“…Wolbachia and the beetle hosts may have an unstable relationship leading to the lack of a clear effect of Wolbachia infection on the host's ecology and phylogeny (Kajtoch et al, ). However, even in a short period of infection, mitochondrial hitchhiking effects driven by Wolbachia are commonly observed in beetles (Ali et al, ; Arthofer, Avtzis, Riegler, & Stauffer, ; Jäckel, Mora, & Dobler, ; Mazur et al, ) and other arthropods (Avtzis et al, ; Cariou, Duret, & Charlat, ; Narita et al, ; Rousset, Vautrin, & Solignac, ; Shoemaker, Dyer, Ahrens, McAbee, & Jaenike, ).…”

Population genetic structure and intraspecific genetic distance of Periplaneta americana (Blattodea: Blattidae) based on mitochondrial and nuclear DNA markers

“…The analysis of COI and wingless fragments defined only 17 haplotypes from 741 individuals and 7 alleles from 113 individuals, respectively. Low population variation is common in other insects (Mazur et al, ; Žitko, Kovaćić, Desdevises, & Puizina, ). Several aspects can explain such a pattern of genetic variation: the small size of the founding populations (Žitko et al, ); the low genetic diversity in the original source populations (Vargo et al, ); and extensive insect control measures involving insecticides and source reduction (Prijović et al, ).…”

Preliminary evidence of the horizontal transmission of Wolbachia between Crioceris leaf beetles (Coleoptera: Chrysomelidae) and their Asparagus host plants

“…Moreover, the allelic profi les found in the weevil Eusomus ovulum [which occupies the same habitat as infected Crioceris species (Mazur et al, 2016)] and in Oreina cacaliae [the only European leaf beetle with a full allelic profi le in the MLST database (Montagna et al, 2014)] were added to this set of MLST sequences. We then used the generated alignment of MLST genes for the construction of phylogenetic trees starting with two datasets: (i) full-length sequences from Crioceris and MLST database references; (ii) shorter alignments that included strains found in Crioceris and Asparagus tissues.…”

“…All PCRs targeting Wolbachia were done using DNAs from Polydrusus inustus and Eusomus ovulum as a positive control. These species are known to be infected by Wolbachia (Mazur et al, 2016). For the host plants, DNA quality was assessed by amplifi cation of chloroplast DNA using primers for the trnL intron.…”