Enhanced heat tolerance of viral-infected aphids leads to niche expansion and reduced interspecific competition.

Vector-borne pathogens are known to alter the phenotypes of their primary hosts and vectors, with implications for disease transmission as well as ecology. Here we show that a plant virus, barley yellow dwarf virus, increases the surface temperature of infected host plants (by an average of 2 °C), while also significantly enhancing the thermal tolerance of its aphid vector Rhopalosiphum padi (by 8 °C). This enhanced thermal tolerance, which was associated with differential upregulation of three heat-shock protein genes, allowed aphids to occupy higher and warmer regions of infected host plants when displaced from cooler regions by competition with a larger aphid species, R. maidis. Infection thereby led to an expansion of the fundamental niche of the vector. These findings show that virus effects on the thermal biology of hosts and vectors can influence their interactions with one another and with other, non-vector organisms.