DISTRIBUTION OF POLYPLOID VARIATION IN BIG BLUESTEM (ANDROPOGON-GERARDII, POACEAE) ACROSS THE TALLGRASS PRAIRIE REGION

The objective of this research was to describe the distribution of polyploid cytotypes of the grass big bluestem (Andropogon gerardii Vitman) along an east-west transect across the tallgrass prairie region, as an integral part of understanding the function of intraspecific polyploid polymorphism. Andropogon gerardii shows intraspecific variation in amount of nuclear DNA as a result of intraspecific polyploidy. Nearly 600 plants from 15 prairies in 5 states were collected and nuclear DNA was determined by flow cytometry. In the eastern part of the tallgrass prairie region, higher polyploids were rarely found. However, at the western edge of the tallgrass of the Missouri River, plants with high nuclear DNA values comprised about half of the plants sampled and in one native prairie formed 82% of the population. Although the bluestem is historically the dominant grass throughout this region, it is extremely variable only on the western extreme of region.