||Genetic variation was surveyed within and between native populations of little bluestem (Schizachyrium scoparium (Michx.) Nash [ = Andropogon scoparius Michx.]) and Virginia wild rye (Elymus virginicus L.), using random amplified polymorphic DNA (RAPD) markers. The native populations of each species included collections from both northeastern and midwestern regions within the United States. Analysis of molecular variance (AMOVA) technique showed
that little bluestem populations were highly variable within populations, whereas Virginia wild rye populations were relatively uniform within populations. Furthermore, when the two species
were compared, an interesting relationship was observed between the genetic distance among populations and the geographic origin of the populations. Little bluestem exhibited a positive correlation, and thus its populations became more genetically different the further populations were separated by geographical distance. Virginia wild rye populations lacked such correlation, and thus populations between widely separated regions could exhibit genetic relationships that
were, in some cases, more similar than populations within a region.
Partitioning of genetic variability within and among populations across regions is, in large part, a function of the breeding system of the species. Little bluestem possesses an open pollinated,
out crossing breeding system, whereas Virginia wild rye is a self-pollinated, inbreeding species. Thus, the reproductive biology of native plants governs the genetic structure observed among populations within a species. As such, a speciesí reproductive biology is a vitally important parameter to consider when replenishing or replacing locally adapted gene pools.