The effect of Wolbachia on lifetime reproductive success of parasitoid wasps

The bacterium Wolbachia is found in a wide range of invertebrates. To enhance its transmission, Wolbachia has evolved a variety of reproductive manipulations of its hosts. Due to its wide distribution and diverse phenotypes, Wolbachia is considered important in the evolution of sex determination and speciation. A fundamental question is what is the effect of Wolbachia on the fitness of their host? Laboratory studies showed that Wolbachia may have positive, negative or no effect on the fitness of their hosts. However, it is not certain whether these results pertain to natural conditions. The parasitoid wasp Anagrus sophiae that parasitizes the eggs of planthoppers is a good model to address these questions. Some wasp populations consist almost entirely of females because nearly all wasps carry a Wolbachia strain that induces asexual reproduction (i.e. parthenogenesis), while in other populations sex ratio is close to normal. We developed a method to estimate the lifetime reproductive success of these wasps by collecting females soon after they die and counting the number of eggs left in their ovaries. Additionally, we established a protocol to extract DNA from wasps of known eggloads to determine Wolbachia titer from individual females. We intend to use these methods to study the effect of Wolbachia on the realized fitness of wasps from different populations. According to theory, we predict that Wolbachia will be less virulent in highly infected populations than in those of intermediate prevalences. We will present a literature survey on the effect of Wolbachia on host fitness, our detailed proposal and preliminary results.