Endosymbiont effects on vector manipulation by insect‐borne plant viruses

Abstract Insect‐vectored plant viruses frequently alter plant–insect interactions in ways favourable to their own transmission (often referred to as manipulation). Variation in virus‐induced effects is often attributed to genetic variability and local adaptation in virus and host‐plant populations, but emerging evidence suggests that vector‐associated microbial symbionts may also play important roles. Vector insects harbour both obligate and facultative endosymbionts that can strongly influence vector traits and their interactions with host plants. Yet relatively few studies to date have examined how endosymbionts influence virus effects on plant–insect interactions and transmission. We argue that endosymbionts are often a key component of the selective environment experienced by vectors and viruses and hypothesize that they may play important roles in modulating the direction and magnitude of virus‐induced effects on plant–insect interactions. We outline key questions and priorities for research that will integrate virus–endosymbiont interactions into disease ecology. Such integration is crucial for understanding the evolution and ecology of viral and endosymbiont effects on vector biology, as well as the implications for disease transmission in agricultural and natural systems.