Location, location, location: stripe position effects on female sword preference

The evolution of complex signals via sexual selection is becoming a primary focus in mate choice studies. Male swordtail fish, Xiphophorus helleri, have a secondary sexual trait, the sword, which is a composite trait consisting of four components favoured by sexual selection via female mate choice. The components include three coloured stripes and size. Although a complete sword is most attractive to female green swordtails, females prefer partial swords containing complete black stripes to incomplete swords lacking black coloration. Female swordtails also prefer longer swords. We addressed how subcomponents of the sword affect female mate choice. Digitally altered videos were used to investigate whether females respond differently to swords with proximal black stripes than to swords with distal black stripes. Although females preferred complete swords to both of the stimuli with partial stripes, they preferred males with distally striped swords to males with proximally striped swords. These results are discussed in light of hypotheses concerning the evolution of mating preferences for multicomponent traits. This study contributes to the growing body of information regarding the response of females to multicomponent visual traits.