Using fish to understand how cities affect sexual selection before and after mating

Urbanization transforms natural and agricultural areas into built landscapes. Such profound habitat alteration imposes strong pressure on phenotypic trait changes through processes related to and/or sexual selection. Evidence of how selection drives traits in urban biota is increasing, but little known about the role In this study, we assessed effect urbanization expression interaction males' pre-mating (body size color) a post-mating (sperm load). We used widespread invasive species, guppy ( Poecilia reticulata ), which wellknown model for studying selection, have never been studied systems purpose. found that did not affect mean body or condition, it resulted size-dependent reductions orange iridescent colors, as well sperm load. The color was reduced small guppies, while colors were large guppies compared non-urban guppies. difference load only males, with lower relationship between positive negative association followed opposite pattern. Our findings suggest pre- weaker than interactions such are context dependent. These responses can be pollution altered visual environment provide an opportunity advance our understanding mechanisms determining adaptation cities.