I started my PhD at the department of Etology and Conservation of Biodiversity (EBD-CSIC) in January under the supervision of Francisco García González. Sexual selection favors the evolution of traits involved in reproduction and underlies the development of complex interactions between males and females. Polyandry has a key role in sexual selection. It allows sexual selection to continue after copulation through post-copulatory sexually selected processes (cryptic female choice and sperm competition) that determine reproductive success. This thesis will shed light on the mechanisms underlying the origin and maintenance of polyandrous behaviour, and will investigate the genetic variance in female mating rates and the relation between mating system and sexual conflict dynamics. I am interested in the study of sexual conflict, based on the differences in the evolutionary interest of both sexes and its consequences. Interestingly, it may lead to antagonistic sexual coevolution. While males develop traits for increasing their efficacy ensuring the paternity of major number of descendents, females develop traits to avoid male control over copulation. To this end, we will use bean beetles, Callosobruchus maculatus, as study system and will carry out innovative experimental evolution approaches combined with quantitative genetic experimental designs.