Bacterial Communities in the Heads and Gasters of 26 Ant Taxa

Insect-associated bacterial communities can vary with host diet, phylogeny, and body region. In this study, we used 16S ribosomal RNA (rRNA) gene amplicon sequencing and a host phylogenetic tree constructed from mitochondrial genes to analyze bacterial communities in whole-head and whole-gaster samples from 26 ant taxa, including 23 honeydew-associated taxa and three dietary comparators. Pseudomonadota was the predominant phylum across most sampled taxa and samples. Chao1 richness and Shannon diversity were significantly higher in head samples than in paired gaster samples, whereas the overall difference in bacterial community structure between body regions was significant but small. No uniform bacterial profile was shared by all 23 honeydew-associated taxa. Gaster bacterial community structure showed significant congruence with host phylogeny, whereas no significant congruence was detected in head communities. Certain bacterial taxa exhibited patterns associated with specific hosts or body regions, including Candidatus Blochmannia in Camponotini gasters, and Fructilactobacillus in the heads of Oecophylla smaragdina. Overall, bacterial communities differed markedly among host taxa and showed more limited variation between body regions, providing a comparative basis for further studies of ant-associated bacteria.