DISJUNCT POPULATIONS OF TRIFOLIUM BECKWITHII (FABACEAE) IN EASTERN SOUTH DAKOTA: VICARIANCE OR RECENT LONG-DISTANCE DISPERSAL? A PRELIMINARY ANALYSIS

Trifolium beckwithii Brewer ex. S. Wats, is widespread in the Sierra Nevada and northern Rocky Mountains but five disjunct populations have existed for at least a century in a considerably different habitat in eastern South Dakota. Genetic divergence of these populations was expected. RAPD profiles were compared between South Dakota and two montane populations. Unexpectedly, measures of genetic similarity between South Dakota and northern California populations were twice as great as those between South Dakota and southern Idaho populations. These data can be interpreted as an indication that T. beckwithii has been introduced relatively recently into South Dakota from a population genetically similar to the one sampled from northern California.