Females trained on red food prefer red male ornaments: sensory exploitation in the swordtail characin (#38)
Despite extensive research in the field of sexual selection, the evolutionary origin of preferences for sexual ornaments is still debated. The sensory exploitation hypothesis states that a pre-existing behavioural bias which is under natural selection may have the side-effect of generating a preference in a sexual selection context. As environmental conditions differ between populations, sexual preferences resulting from natural selection are expected to vary as well. The swordtail characin (Corynopoma riisei) is a tropical fish species in which males use a food mimicking ornament to attract females. We investigated how female foraging experiences are associated with preference for this male ornament. We trained females on a diet consisting of either red-coloured food or standard-coloured green food items. Owing to large variation among males in display rate, we tested female response to the male ornament using several techniques. First, we presented the females with a video animation showing males with normal and red-coloured ornaments. Next, we placed real males with artificially red-coloured ornaments in display position in an experimental box that constrained the males' ability to move. Lastly, the males were released and allowed to interact freely with the females. We found a rapid and strong response in preference for the male ornament according to food treatment. These results provide strong experimental support for a direct link between variation in feeding experience and female attraction to male ornaments and thus support a role for sensory exploitation behind the evolution and maintenance of this ornament.