show Abstracthide AbstractIn this study, we investigated the relationship between gene family expansions and a symbiotic partnership aphids have with the bacterium Buchnera aphidicola. Aphids are sap-feeding insects and rely on Buchnera for nutrients, including essential amino acids. Interestingly, aphids also have experienced many gene duplications in their amino acid transporters. Amino acid transporter duplication has been hypothesized to be driven by selection for amino acid transporters to operate in symbiosis, mediating nutrient exchange between aphids and Buchnera. We used a comparative transcriptomic approach to determine when in aphid evolution the amino acid transporters duplicated and if expression in the aphid cells housing Buchnera was conserved across different aphid species. This study addresses how an organism''s natural history and ecological traits can shape its genome architecture.