Rapid weed adaptation and range expansion in response to agriculture over the last two centuries

North America has seen a massive increase in cropland use since 1800, accompanied more recently by the intensification of agricultural practices. Through genome analysis of present-day and historical samples spanning environments over the last two centuries, we studied the impact of these changes in farming on the extent and tempo of evolution across the native range of common waterhemp ( Amaranthus tuberculatus) , a now pervasive agricultural weed. Modern agriculture has imposed strengths of selection rarely observed in the wild, with striking shifts in allele frequency trajectories since agricultural intensification in the 1960s. An evolutionary response to this extreme selection was facilitated by a concurrent human-mediated range shift. By reshaping genome-wide diversity across the landscape, agriculture has driven the success of this weed in the 21 st -century. One Sentence Summary Modern agriculture has shaped the evolution of a native plant into a weed by driving range shifts and strengths of selection rarely observed in the wild.