Integrating Host Phylogeny and Bacterial Detection Patterns Reveals Contrasting Associations of Buchnera aphidicola and Other Aphid-Associated Bacteria.

Aphids are important agricultural pests that interact with diverse bacterial taxa living within or associated with their bodies. Some bacteria, such as the obligate symbiont Buchnera aphidicola, provide essential nutritional functions and are predominantly inherited vertically, whereas other aphid-associated bacteria may have more variable distributions and ecological roles. In this study, we investigated patterns of association between aphid evolutionary relationships and selected bacterial taxa. Aphids were identified using morphological characteristics and mitochondrial cytochrome c oxidase subunit I (COI) sequences, and host phylogenetic relationships were reconstructed using mitochondrial DNA data. We then compared the host phylogeny with that of the obligate symbiont Buchnera aphidicola based on 16S rRNA sequences and screened aphid specimens for selected aphid-associated bacteria (Wolbachia, Pantoea, and Arsenophonus) using diagnostic PCR assays. The host and Buchnera phylogenies showed significant global congruence, consistent with a strong long-term host-associated evolutionary relationship and predominantly vertical inheritance of Buchnera. In contrast, the selected aphid-associated bacteria showed heterogeneous detection patterns across the sampled aphid taxa. Pantoea was detected relatively frequently and across a broad range of sampled hosts, whereas Wolbachia and Arsenophonus showed more variable and restricted detection patterns. Given the small and uneven sample sizes among aphid species, these findings are interpreted as descriptive screening patterns rather than species-level prevalence estimates. Overall, the results highlight contrasting patterns of host-associated evolution between Buchnera and other aphid-associated bacteria and provide a basis for further investigation of the ecological and evolutionary processes underlying these associations.