A comparative approach will be used to assess the evolutionary relationship between aggression and male size across the nine species of northern swordtail fishes. Dyadic contests and mirror image stimulation tests will be used to measure aggression levels. The relationship between the mean male size of each species and the two measures of aggression will be analyzed using the comparative method of independent contrasts to determine if male size and aggression have been coevolving. In addition, the response of males to a signal of aggressive intent (vertical bars) will be examined to determine if this signal confounds the relationship between aggression and size. This study is important because it will examine the role that male-male competition has played in the evolution of male size, while examining the possible effects of a signal and phylogeny on aggression. In addition to graduate training, undergraduates participate in collection trips to Mexico, project design, data collection and are included as authors on publications for which they have made a substantial and intellectual contribution. This project also includes international collaboration, with students and researchers from both countries benefiting from in-field interactions and dissemination of research at each others home universities.
