Flipping the Script: Wolbachia Favoring Males in a Neotropical Drosophila

As skilful strategists, intracellular endosymbionts, particularly Wolbachia, have evolved the ability to induce phenotypes that frequently enhance the fitness of female hosts, often at the cost of male fitness, to ensure the transmission to subsequent host generations. Natural selection plays a pivotal role in this interaction, potentially amplifying, diminishing, or eradicating endosymbionts based on their impact on host fitness. This study investigated the relationship between the Wolbachia strain wStv Vi and Drosophila sturtevanti, the most abundant Neotropical drosophilid. We combined field sampling and controlled crosses of Wolbachia-infected and antibiotic-treated individuals to assess the endosymbionts host effects. We found that contrary to initial expectations, Wolbachia reduced female fecundity while boosting male fertility, yielding a similar number of offspring in both infected and treated pairs. However, infected females produced fewer larvae when crossed with treated males. A key observation was protogyny in treated but not infected individuals, suggesting Wolbachias influence on host ontogeny, potentially increasing mating among infected siblings and restoring infected females fitness. From these results, we concluded that this whole strategy balanced the fitness of infected and non-infected pairs. In fact, repeated sampling, at the same site, revealed fluctuations in Wolbachia prevalence and high, but not perfect, vertical transmission. Our results indicate that the strategies for persistence in a particular host extend far beyond favoring females. They also imply that environmental factors may favor one group over another in varying circumstances, potentially explaining the observed fluctuations in infection and variable prevalence of Wolbachia in D. sturtevanti populations.