Strong Linkage Between Symbiotic Bacterial Community and Host Age and Morph in a Hemipteran Social Insect

The relationships between symbionts and insects are complex, and symbionts usually have diverse ecological and evolutionary effects on their hosts. The phloem sap-sucking aphids are good models to study the interactions between insects and symbiotic microorganisms. Although aphids usually exhibit remarkable life cycle complexity, most previous studies on symbiotic diversity sampled only apterous viviparous adult females or very few morphs. In this study, high-throughput 16S rDNA amplicon sequencing was used to assess the symbiotic bacterial communities of eleven morphs or developmental stages of the social aphid Pseudoregma bambucicola. We found there were significant differences in bacterial composition in response to different morphs and developmental stages, and for the first time, we revealed male aphids hosted very different symbiotic composition featured with low abundance of dominant symbionts but high diversity of total symbionts. The relative abundance of Pectobacterium showed relatively stable across different types of samples, while that of Wolbachia fluctuated greatly, indicating the former may have a consistent function in this species and the latter may provide specific function for certain morphs or developmental stages. Our study presents new evidence of complexity of symbiotic associations and indicates strong linkage between symbiotic bacterial community and host age and morph.