Sexual conflict over mating duration and frequency in Zygogramma bicolorata

Abstract

Duration and frequency of mating are the most prominent aspects of mating behaviour over which sexual conflict can occur. Parthenium beetle (Zygogramma bicolorata) exhibits an extremely high mating rate, with each mating typically lasting several hours. We investigated mating behaviour in this beetle to assess if there is sexual conflict. Theories of sexual conflict predict that such mating behaviour, while being beneficial to the males, should be detrimental to the females with regard to reproduction and/or survival. We experimentally manipulated the length and number of matings, and examined the effect on fecundity and survivorship of the females. While long mating has previously been identified as a mate-guarding strategy that benefits the males, our data reveal that it is detrimental to female fitness, supporting the sexual conflict hypothesis. Further, we checked natural variation in mating duration and its correlation with key fitness components. Our results show that female longevity is negatively correlated to reproductive rate, but positively correlated to lifetime reproduction. We argue that such a pattern is consistent with sexual conflict. While being the first clear demonstration of sexual conflict in this species, we discuss its significance, including a potential role in reducing its efficacy as a biocontrol.