Ranunculus triternatusoccurs as a few isolated populations in Washington, Oregon, Idaho, and Nevada. We have used RAPD (randomly amplified polymorphic DNA) polymorphisms to measure genetic diversity among 25 individuals from one population from Columbia Hills Preserve near Goldendale, WA. For comparison, we have also examined 25 individuals from a population of the widespread sagebrush buttercup, Ranunculus glaberrimus. Using ten different 10-mer primers with the 50 DNAs, we generated a total of 87 different RAPD bands. Thirty-two bands were common to the two species; whereas 37 were unique to R. triternatusand 17 were unique to R. glaberrimus. The rare species,R. triternatus, has a higher number of variable loci (62% polymorphism versus 22% for R. glaberrimus), a higher proportion of genetically distinct individuals (100% R. triternatus vs. 88% for R. glaberrimus), and a greater average genetic distance among individuals (0.19 for R.triternatusvs. 0.06 for R. glaberrimus). Thus, this rare species, considered a species of concern in Washington State, does not seem to be suffering from reduced genetic diversity as compared to the widespread species. In addition to showing a higher level of genetic diversity among members of the rare species, the RAPD data also support the separateness of the two species. As only one population of each species has been tested, this last contention will need to be further investigated by examining samples from additional populations of each species. This further sampling is currently underway.

Key words: genetic diversity, Ranunculus triternatus , RAPDs