Costs and benefits of symbiosis between a bean beetle and Wolbachia

• Wolbachia produce cytoplasmic incompatibility (CI) in Callosobruchus chinensis.
• Wolbachia have positive effects on the host's life history and reproductive traits.
• Wolbachia benefit C. chinensis by increasing its fitness in conjunction with CI.

Wolbachia are a major symbiont of arthropods and nematodes. They can manipulate host reproduction in order to spread in host populations, but Wolbachia manipulation often incurs costs to the host species itself and/or provides benefits to the host. Because the fitness effects of Wolbachia infections differ between host species, fitness components of the host have to be carefully investigated. However, it is still relatively understudied. Here, we investigated effects of Wolbachia infection on life history and reproductive traits in Callosobruchus chinensis. This is a host in which the prevalence of Wolbachia and the cytoplasmic incompatibility (CI) it causes have been well reported. However, excluding research related to CI, there is little information about the effects of Wolbachia infection on traits of C. chinensis. We found that Wolbachia infection had positive effects on the life history and reproductive traits of C. chinensis males and females, with the exception of a negative effect on female fecundity. Nevertheless, Wolbachia-infected females are thought to have the advantage of reproduction because of complete CI in eggs from an uninfected female mated with an infected male. These results suggest that Wolbachia infection affects the life history and sexual selection of C. chinensis populations.