Biased parasitoid sex ratios: Wolbachia, functional traits, local and landscape effects

Abstract

Adult sex ratio (ASR) is a demographic key parameter, being essential for the survival and dynamics of a species populations. Biased ASR are adaptations to the environment on different scales, resulted by different mechanisms as inbreeding, mating behaviour, resource limitations, endosymbionts such as Wolbachia, and changes in density or spatial distribution. Parasitoid ASRs are also known to be strongly biased. But less information is available on large scale variable effects such as landscape composition or fragmentation. We aimed to study whether the landscape scale does affect the ASR of parasitoids belonging to the same tritrophic gall inducer community. We examined effects of characteristics on different scales as functional trait, local and landscape scale environment on parasitoid ASR. On species level ovipositor length, on local scale resource amount and density, while on landscape scale habitat amount, land use and landscape history were the examined explanatory variables. We controlled for the incidence and prevalence of Wolbachia infections. Parasitoid ASR is best explained by ovipositor length: with which increase ASR also increases; and available resource amount: with the gall diameter increase ASR decreases. On large scale the interaction of functional traits with habitat size also explained significantly the parasitoid ASRs. Our results support the hypothesis that large scale environmental characteristics affect parasitoid ASRs besides intrinsic and local characteristics.