ABSTRACT
Species are generally regarded as having a single, typical and characteristic chromosome number and nuclear DNA content. Indeed, the species-specific nuclear DNA content is referred to as the constant value. This chapter investigates polyploid polymorphism in The Great Plains generally, and focuses on a single case. It compares the evidence for polyploid polymorphism in three major families, the Poaceae, Asteraceae and Fabaceae, of North American grasslands. Since macrogeographic patterns must ultimately be produced by forces acting on individual plants, the chapter explains the distribution of intraspecific polyploidy within and between sites across the range of one species, big bluestem, Andropogon gerardii. The results of these two investigations are aimed at determining the function, if any, of intraspecific polyploid polymorphism, and determining whether intraspecific polyploidy is an adaptive strategy of some sort, a transitory state indicating evolution or speciation in progress, or a selectively neutral condition.
