Female preference for dynamic traits in the green swordtail, Xiphophorus helleri

Abstract. Analyses of the relationship between female preference and male behaviour have been complicated by correlated variation in factors such as male size and appearance. This study examined the eVects of systematically manipulating male behaviour, while holding male morphology constant. Female green swordtails were shown video-recorded sequences of the same male engaging in an active courtship display, performing similar levels of feeding activity, and remaining inactive. Control sequences of moving food particles and of an empty aquarium were also presented. Female responsive-ness was significantly diVerent across time intervals (before, during and after the stimulus) for the three stimuli showing a male, but not for the two controls. Analyses of female behaviour patterns during the stimulus presentations revealed that they preferred sequences of courting males to all other stimuli. Females did not respond diVerently to the feeding and inactive sequences. These results indicate that female interest depends upon a specific set of motor patterns, and suggest that male behaviour and morphology may act synergistically to determine female preference. Video stimuli should prove useful in future experiments seeking to identify the role of specific courtship motor patterns in mate choice.? 1996 The Association for the Study of Animal Behaviour Recent models of sexual selection have considered the role of perceptual mechanisms in the evolution of sexually dimorphic traits. Ryan (1990) pro-posed that secondary sexual characteristics can evolve to exploit pre-existing sensory biases within individuals of the opposite sex, and Endler (1992) examined the evolution of male morphology in terms of constraints imposed by environmental parameters and predator pressures. Support for these models has been found in a variety of systems involving both visual signals (Basol