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 group members: focal individuals adjusted their exploratory behavior to match that of group members who were the same genotype as the focal, but, changed their exploratory behavior to differentiate from partner-genotype group members. Exploratory behavior also depended on the identities of both genotypes that composed the group. Together, these findings demonstrate genotype-by-genotype epistasis for exploratory behavior both within and among groups.
Methods
Please see manuscript for details on data collection.