In the 19th century, the Great Plains were ~500,000 square miles of prairie, steppe, and grasslands that stretched from northern Mexico to southern-central Canada. North of the 50th parallel, the boreal forest still occupies a wide swath of North America comprised of coniferous forest interspersed with vast wetlands, mostly lakes, rivers, bogs, and fens. At that time, the American bison once occurred across the full scope of these vast continental ecosystems. Across all these lands, waters, and places; were all these bison the same species, the same animal? Indeed, when are bison not exactly the same?
Through extensive long-term natural history studies and scientific investigations, even to the genetic and cellular levels, we now understand that there is one species of bison that is comprised of two subspecies in North America and another species of bison in Europe. The American bison that evolved and lived across the vast plains and woodlands are aptly named - the plains bison (genus: Bison, species: bison, subspecies: bison) and wood bison (genus: Bison, species: bison, subspecies: athabascae). So for someone who really pays close attention to formal taxonomy, it is about as simple as it gets. Bison bison bison - for the animals that evolved and lived primarily on the Great Plains and Bison bison athabascae - for the animals that evolved and lived primarily in the boreal forest. "Athabascae" is a formal taxonomic name that recognizes the anglicized version of the Cree native name for vast Lake Athabasca and surrounding watershed in Canada, "athap-ask-a-w," that means "grass or reeds here and there."