Figure 1.

Collection locations of Isatis tinctoria in the western USA. Shaded counties in the western USA have noted presence of this species at some time. The inset shows collection locations from the eastern USA. Black dots show collection location (exact coordinates are in Supporting Information—Table S1) and yellow or blue shapes indicate majority genetic cluster assignments of plant as well as number of plants collected for a location. Regions 1, 2 and 3 approximate the major invaded areas and are shown by dashed lines.