Pervasive indirect genetic effects on behavioral development in polymorphic eastern mosquitofish

The social environment can dramatically influence development and expression of individual behavior. Indirect genetic effects (IGE) arise when variation in the social environment depend on genotypic differences among social partners. Their role in generating variation and in influencing evolutionary dynamics has become increasingly recognized in recent years, but less attention has been paid to how indirect genetic effects arise during development. Here, we measure IGE during development using a discrete natural polymorphism in male coloration and associated behaviors in eastern mosquitofish (Gambusia holbrooki). The experiment revealed substantial IGE and direct genetic effects on behavior. For some behaviors, IGE changed and even reversed direction over the 16 weeks of the experiment, indicating important developmental dynamics. Interaction between IGE and direct genetic effects for some behaviors indicated that melanistic males were less responsive to a genetic change in their social...