The social influence on, and genetic architecture of, copulation in Callosobruchus maculatus

Carly Wilson

    Research output: ThesisDoctoral Thesis

    330 Downloads (Pure)

    Abstract

    [Truncated] The evolutionary interests of males and females are rarely harmonious. Males and females often evolve to adjust their behaviour or physiology to enhance their reproductive success, often at the expense of the other sex. Sexual conflict is where these adaptations have antagonistic fitness consequences to the opposite sex. In this thesis, I use a population of the seed beetle, Callosobruchus maculatus, to investigate the plasticity of copulatory behaviours and fitness measures in differing sociosexual environments. Initially, C. maculatus was thought to have a sexual conflict over copulation duration as females have a conspicuous pericopulatory kicking behaviour and the aedeagus of the male has sclerotized spines that damage female internally. This thesis comprises a range of phenotypic experiments where I exposed male and female C. maculatus to differing sociosexual environments in which I quantified any changes to copulatory behaviours and fitness measures. The final chapter estimates the quantitative genetic variances and covariances of these behaviours.
    I found that the female kicking behaviour is not fully under the control of females; in fact phenotypically, males control all of the measured copulatory behaviours including kicking latency and kicking duration. Furthermore, by introducing a harassing trio of males into the mating environment, females kicked for twice as long without any reduction in the overall copulation duration. These results dispel the idea that pericopulatory kicking by females is an effective resistance adaptation evolved by females in response to damage caused by spiny male aedeagi during copulation. Indeed, females that could kick for longer died sooner suggesting that female kicking may be a trait that benefits male fitness at a cost to female fitness.
    By modelling the changes in the pattern of ejaculate transfer, I showed that the probability of a female kicking is independently positively influenced by ejaculate weight, kicking latency and the number of mates with which a male has previously mated. Males also showed plasticity in ejaculate transfer with sociosexual environment, as males mating with harassing males present began transferring ejaculate sooner than males mating in isolation. In addition, males that were not kicked during copulation (i.e. females had their hind legs severed preventing kicking) transferred their ejaculates at a slower rate than males mating with intact females.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2014

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