The effects of relatedness on offspring sex ratio in pollinating fig wasps

Background: Sex ratio theory predicts a more female-biased sex ratio if the haplodiploid foundresses of pollinating fig wasps are siblings when those foundresses oviposit in a local patch. Question: Do pollinating fig wasps adjust their offspring sex ratio in response to their relatedness to other nearby ovipositing fig wasps'? Organisms: Ceratosolen solmsi Mayr, an obligate pollinator of the functionally dioecious fig tree, Ficus hispida Linn. Methods: From May to October 2007, we reared pollinators from a single foundress through five generations. We collected male syconia before they matured and placed them in a fine-mesh bag. We used female pollinators that emerged. Our protocol ensured that females were sibs at each stage. We counted female and male wasps, galls, bladders (inflated, hollow ovules), and total female flowers in 25% of each syconium. More than 10 syconia were obtained in each generation. For comparison, we ran a non-sibling foundress treatment in July and August 2007. We analysed the data using a generalized linear model Results: Offspring sex ratio was similar among the five sibling mating generations in our experiments, and the offspring sex ratio in the local mate competition models with sibling foundresses and non-sibling foundresses was also similar. The offspring sex ratio increased in the presence of more foundresses. Conclusion: Ceratosolen solmsi does not adjust its offspring sex ratio according to sibling relatedness.