Sexual conflict in the Bean Weevil, Callosobruchus maculatus.

This study used the bean weevil, Callosobruchus maculatus, to examine the functions, causal relationships and life-history consequences of aspects of reproductive morphology and behaviour within the framework of sexual conflict theory. In Chapter 2, the gross genital anatomy of male and female C. maculatus are described. Sharp cuticular spines on the male intromittent organ unfurl within the female genital tract during copulation. Chapter 3 established a causal relationship between the male intromittent and damage to the female genital tract. The extent of genital damage varied among once-mated females and increased with each additional copulation. Chapter 4 investigated the 'function of female mate-kicking behaviour, whereby females kick their mates during copulation. Females prevented from kicking had longer copulations and more genital damage than females permitted to kick, suggesting that mate-kicking has evolved as a counter-adaptation to ameliorate the associated costs. The effect of mate-kicking on two female post-copulatory traits linked to both male and female fitness were examined in Chapter 5. No measurable effects due to mate-kicking were found on either the immediate oviposition rate or the remating interval of females following an initial copulation. These findings indicate that males do not appear to induce favourable changes in female post-copulatory behaviour through the imposition of longer copulations or increased genital damage. In Chapter 6, the effect of varying exposure to males on female fitness traits was examined. With oviposition rates partially standardised across mating frequencies, remated females had shorter lifespans than once-mated females, but the relationship between copulation frequency and lifespan was not linear. With standardised gregarious living conditions, female reproductive output increased with greater opportunities to mate. Thus, despite the apparent longevity cost associated with copulation, females elevate their fitness through multiple mating and increased exposure to males. The potential for non-mating exposure to males to reduce female fitness traits was also demonstrated. Finally, Chapter 7 assesses the evidence for a conflict between the sexes in C. maculatus over male damaging tactics.