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Wolbachia manipulate the reproduction of their arthropod hosts in a variety of ways. Recent work has demonstrated that these bacteria may combine phenotypes – possessing a ‘male killing’ phenotype and, where males survive, induce cytoplasmic incompatibility (CI). We here develop a mathematical model to investigate the extent to which ‘hidden’ CI may affect the evolutionary dynamics of host genes that suppress male-killing activity. We observed that for high prevalence infections, CI drives both suppressor and bacterium to higher frequency, such that the strain appears to solely exhibit CI. In contrast, for low prevalence infections, CI impedes suppressor invasion as surviving infected males are incompatible with the majority of females in the population. Our results demonstrate that ‘hidden’ phenotypes as well as observable ones can impact on the dynamics of the interaction, and knowledge of these is therefore required to predict when suppressor genes will invade, and the consequences of their invasion. [ABSTRACT FROM AUTHOR]

Asymmetric gene flow is generally believed to oppose natural selection and potentially impede adaptation. Whilst the cause of asymmetric gene flow has been seen largely in terms of variation in population density over space, asymmetric gene flow can also result from varying sex ratios across subpopulations with similar population sizes. We model the process of adaptation in a scenario in which two adjacent subpopulations have different sex ratios, associated with different levels of infection with maternally inherited endosymbionts that selectively kill male hosts. Two models are analyzed in detail. First, we consider one host locus with two alleles, each of which possesses a selective advantage in one of the subpopulations. We found that local adaptation can strongly be impeded in the subpopulation with the more female biased population sex ratio. Second, we analyze host alleles that provide resistance against the male-killing (MK) endosymbionts and show that asymmetric gene flow can prevent the spread of such alleles under certain conditions. These results might have important implications for the coevolution of MK bacteria and their hosts. [ABSTRACT FROM AUTHOR]

Characterizes the ribosomal DNA gene in the ladybird Harmonia axyridis to determine male-killing agent. Identification of single bacterial type association with male-killing in H. axyridis; Phylogenetic position of the H. axyridis male-killer; Association of bacterial presence and male-killing.

Wolbachia is one of the most common endosymbionts found infecting arthropods. Theory predicts symbionts like Wolbachia will be more common in species radiations, as host shift events occur with greatest frequency between closely related species. Further, the presence of Wolbachia itself may engender reproductive isolation, and promote speciation of their hosts. Here we screened 178 individuals belonging to 30 species of the damselfly genera Nesobasis and Melanesobasis — species radiations endemic to the Fiji archipelago in the South Pacific — for Wolbachia, using multilocus sequence typing to characterize bacterial strains. Incidence of Wolbachia was 71% in Nesobasis and 40% in Melanesobasis, and prevalence was also high, with an average of 88% in the Nesobasis species screened. We identified a total of 25 Wolbachia strains, belonging to supergroups A, B and F, with some epidemic strains present in multiple species. The occurrence of Wolbachia in both males and females, and the similar global prevalence found in both sexes rules out any strong effect of Wolbachia on the primary sex-ratio, but are compatible with the phenotype of cytoplasmic incompatibility. Nesobasis has higher species richness than most endemic island damselfly genera, and we discuss the potential for endosymbiont-mediated speciation within this group. [ABSTRACT FROM AUTHOR]