Nest volume shapes termitophile abundance in Constrictotermes cyphergaster colonies

Abstract Social insect colonies function as ecological units whose size directly shapes the abundance of associated organisms. The nest volume determines initial colonization success in Constrictotermes cyphergaster, but its impact on post-colonization dynamics remains untested. Here, we sampled 60 arboreal nests across four localities in the Brazilian semiarid to investigate how the volume of this structure shapes termitophile abundance . Our results reveal that nest volume positively predicted the abundance of symbionts:each additional liter increases the expected count by 2.4%, generating an accumulation rate in abundance of nearly five-fold between small and large colonies. Notably, volume did not predict the probability of a nest harboring no termitophiles, indicating that colony size modulates carrying capacity post-colonization rather than facilitating initial invasion. Furthermore, abundance differed among species, with Termitocola silvestrii numerically outnumbering both Corotoca species, and varied across landscape, as urban areas harbored substantially fewer symbionts than rural sites. Interestingly,despite the increase in absolute abundance of symbionts, the ratio of termitophiles per worker remained constant across the entire volume gradient.This pattern suggests active population tracking, host tolerance , or passive chemical integration, hypotheses that now pave the way for testing based on cuticular hydrocarbon profiles. Together, these findings extend our understanding of symbiont ecology, connecting initial colonization to the regulation of population dynamics and framework of termitophile–host interactions.