Decisions that improve genebank management depend on understanding patterns of diversity in the genetic resources being conserved. In potato, populations of the wild Mexican species S. verrucosum (ver) collected from the north (N) of the natural range had been shown to be genetically distinctive from those in the south (S). But this geographic association with genetic diversity was noted to be confounded with proximity of other wild potato species, suggesting introgression as a possible cause. RAPD bands that distinguished N and S ver were generated. When their association with nearby populations of other wild potato species was assessed, the hypothesis of introgression was not supported. We conclude that the apparently distinctive genetics of N ver are not explained by common alleles introgressed from proximal populations of other species. Thus, N ver germplasm populations, although less numerous, should be represented in samples of species ver with regard to collection, preservation and evaluation. © 2008 Potato Association of America.