Genotype-by-genotype epistasis for exploratory behavior in D. simulans

Social interactions can influence the expression and underlying genetic basis of many traits. Yet, empirical investigations of indirect genetic effects (IGEs) and genotype-by-genotype epistasis—quantitative genetics parameters representing the role of genetic variation in a focal individual and its interacting partners in producing the observed trait values—are still scarce. Studying this social plasticity is notoriously challenging when individuals interact in groups, rather than (simpler) dyads. Here, we investigate the genetic architecture of social plasticity for exploratory behavior, one of the most intensively-studied behaviors in recent decades. Using isofemale lines of D. simulans, we measured genotypes both alone, and in social groups representing a mix of two genotypes. We found that females adjusted their exploratory behavior based on the behavior of others in the group, representing social plasticity. However, the direction of this plasticity depended on the identity of gro...