Abstract
Biological invasions can influence ecosystems, yet the evolutionary trajectories and disease dynamics of clonal expansion remain poorly understood. Since its 2011 detection, Metopolophium festucae cerealium (Stroyan), a subspecies of the cereal grass aphid endemic to Europe, has expanded across small grain growing regions of the western U.S. Our field surveys further indicate continued range expansion into previously unreported areas. Here, we integrate population genomics with virus transmission assays to evaluate its invasion structure and potential role in barley yellow dwarf virus (BYDV) transmission. Genome-wide SNP analysis of 262 individuals from six states reveals high genetic homogeneity, supporting a single introduction event and subsequent superclonal expansion. Although M. f. cerealium acquires BYDV at rates comparable to native Rhopalosiphum padi and maintains similar viral titers, it fails to transmit the virus. The primary agroecological risk posed by this invasion is through direct feeding injury, underscoring the need for continued monitoring and refined pest management strategies.