Bacterial 16s rRNA gene amplicon data (V3-V4) and qPCR data

Within a given species, considerable inter-individual, spatial, and temporal variation in the composition of the host microbiome exists. In group-living animals, social interactions homogenize microbiome composition among group members, nevertheless, divergence in microbiome composition among related groups arises. Such variation can result from deterministic and stochastic processes. Stochastic changes, or ecological drift, can occur among symbionts with potential for colonizing a host and within individual hosts, and drive divergence in microbiome composition among hosts or host groups. We tested whether ecological drift associated with dispersal and foundation of new groups cause divergence in microbiome composition between natal and newly formed groups in the social spider Stegodyphus dumicola. We simulated initiation of new groups and compared variation in microbiome composition among and within groups. Theory predicts a decrease in beta diversity with increasing group size, and we...