The collective behavior of ant groups depends on group genotypic composition

Abstract

Increasingly, researchers document variation between groups in collective behavior, but the genetic architecture of collective behavior and how the genotypic composition of groups affects collective behavior remains unclear. Social insects are ideal for studying the effects of genetic variation on collective behavior because their societies are defined by social interactions. To explore how the genetic composition of groups affects collective behavior, we constructed groups of pharaoh ants (Monomorium pharaonis) from 33 genetically distinct colonies of known pedigree. The groups consisted of either all workers from the same single colony or workers from two genetically different colonies, and we assayed the exploration and aggression of the groups. We found that collective behavior depended on the specific genotypic combination of group members, i.e. we found evidence for genotype-by-genotype epistasis for both collective behaviors. Furthermore, the observed collective behavior of groups differed from the additive genetic expectations of groups, further demonstrating the importance of genotype-by-genotype effects. Finally, the collective aggression of the groups was negatively correlated with the pairwise relatedness estimates between workers within the group. Overall, this study highlights that specific combinations of genotypes influence group-level phenotypes and the difficulty of predicting group-level phenotypes using only additive models.