FIGURE 1. Parentage and reciprocal origins of tetraploid species of Tragopogon in North America. Hatched lines indicate diploid(s) contributing chloroplast to the tetraploids.

1995). However, several populations of T. mirus in different locations had the same isozyme multilocus genotype, chloroplast DNA haplotype, and rDNA repeat, and, in many cases, they co-occurred with the diploid progenitor species, T. dubius and T. porrifolius; the same was true of T. miscellus, which co-occurred in at least some locations with both of its progenitors, T. dubius and Tragopogon pratensis. It was possible that these separate locations represented independent sites of polyploid formation from genetically identical (based on the markers at hand) diploids. However, this hypothesis could not be tested without the use of more sensitive markers.

Cook et al. (1998) used random amplified polymorphic DNA (RAPD) markers to test the hypothesis that isozymically identical populations of T. mirus having the same chloroplast DNA haplotype and rDNA repeat were of separate origin and that “identical” populations of T. miscellus also were of separate origin. For T. mirus, five populations with isozyme multilocus genotype 1 (Soltis et al., 1995) and two populations with isozyme genotype 2 (Soltis et al., 1995) were sampled. Each population had a unique RAPD profile (and, in fact, two populations were polymorphic), suggesting that each population may have had a separate origin. Taken with other data, T. mirus may represent a collection of as many as 11 lineages (Cook et al., 1998). RAPD data for three populations of isozyme genotype 1 (Soltis et al., 1995) of T. miscellus demonstrated that all three were distinct and possibly of separate origin, raising the number of genetically distinct populations of T. miscellus to five (Cook et al., 1998).

The Tragopogon tetraploids represent remarkable cases of recurrent formation on a small geographic scale and in a short period, perhaps the