Shana encounters a large infestation of Canada thistle and plots it in her GPS computer. Large areas (greater than 2 acres) are mapped with polygons. A polygon is a many-sided shape—like hexagons or pentagons (Poly = many). Then she enters other characteristics to help scientists understand the ecology of the plant community in which the thistle lives. One important characteristic is the dominant plant species. Researchers record the most abundant plant species found in the infested area. In this case, the dominant species is a rush, a native grass-like plant. Often times the exotic weed is dominant!