Random amplified polymorphic DNA variation among remnant big bluestem (Andropogon gerardii Vitman) populations from Arkansas' Grand Prairie

Random amplified polymorphic DNA (RAPD) analysis was used to characterize g enetic diversity and genetic distinctiveness of Andropogon gerardii from re mnant Arkansas prairies. Six oligonucleotide primers, which generated 37 RA PD bands, were used to analyse 30-32 plants from six Grand Prairie populati ons, Baker Prairie (Arkansas Ozarks), two Illinois prairies and two cultiva rs. Genetic diversity of the Arkansas remnants ranged from 82.7 to 99.3%, w ith 89% of the total genetic variation within and 11% among populations. Th e partitioning of genetic variation was consistent with that reported for o ther outcrossing perennial grasses, using the more conservative allozyme ma rkers. Principal component analysis indicated a northern and southern assoc iation within Arkansas' Grand Prairie. Although there was no genetic struct uring at the landscape level, the Illinois prairies and cultivars were diff erent from all Arkansas prairies tested. There was significant within-popul ation structuring in four of the seven Arkansas remnants, with a negative r elationship between genetic similarity and geographical distance. The three nonstructured populations were from a linear railroad remnant, suggesting different population-level dynamics from nonlinear prairies. The results of this study indicated that small isolated remnant big bluestem populations were not genetically depauperate and that genetic relationships among popul ations could not be predicted solely on geographical proximity.