Do Wolbachia influence fecundity in Nasonia vitripennis?

Area of Science:

• Microbiology and Microbial Ecology
• Insect Genetics and Evolution
• Symbiotic Relationships

Background:

• Wolbachia are vertically transmitted intracellular bacteria that can manipulate host reproduction.
• The parasitic wasp Nasonia vitripennis is a model organism for studying host-symbiont interactions.
• Previous studies suggested potential fitness benefits of Wolbachia infection in N. vitripennis.

Purpose of the Study:

• To investigate the influence of Wolbachia infection on the fecundity of Nasonia vitripennis.
• To control for host genetic background effects on Wolbachia-induced fitness changes.
• To reconcile conflicting previous findings regarding Wolbachia's impact on host fitness.

Main Methods:

• Fecundity of Nasonia vitripennis strains infected with one or two Wolbachia variants (wAv, wBv) was measured.
• Host genetic background was controlled using introgression to replace the genetic makeup of infected and uninfected strains.
• Comparison of offspring production between Wolbachia-infected and uninfected N. vitripennis across different genetic backgrounds.

Main Results:

• Preliminary observations suggested increased fecundity in double-infected females.
• Further experiments failed to consistently demonstrate positive fitness effects of Wolbachia.
• After controlling for host genetic background, no convincing evidence for positive fitness effects of Wolbachia was found.

Conclusions:

• The fecundity effects of Wolbachia in Nasonia vitripennis are likely small or absent when host genetic background is controlled.
• Host genetic background plays a crucial role in mediating the fitness effects of Wolbachia.
• Previous findings of positive fitness effects may have been confounded by host genetic variation.