The pale coneflower, Echinacea pallida (Nutt.) Nutt., is a conspicuous member of the tallgrass prairie community in the eastern Great Plains, USA. In 1968, McGregor published a taxonomic revision of the Echinacea based on extensive morphological, cytological, and biosystematic data. McGregor revealed that unlike most species in the genus, which are diploid, E. pallida was a tetraploid. He also suggested that E. pallida might be an allotetraploid derived from the two diploid species, E. sanguinea Nutt. and E. simulata McGregor. The former occurs in eastern Texas, western Louisiana, and southwestern Arkansas; whereas the latter is nearly restricted to southeastern Missouri. All species are similar morphologically, and the most conspicuous difference between the diploids and the tetraploid is pollen color (bright yellow in the diploids and bright white in the tetraploid). Last summer, we collected leaf samples from roadside populations of all three taxa to try to test McGregor's hypothesis on the origin of E. pallida. Starch gel electrophoresis was used to assay each taxon for allelic variability. In particular, we looked for unique genetic markers in the putative parental taxa that might be inherited and expressed co-dominantly in the allotetraploid. While we have found differences in allelic frequencies among taxa, and interesting allozyme profiles in the tetraploid, we have not found unique marker alleles in the diploids. Although allozyme data generated thus far appear to be insufficient for answering our original question, we are now testing whether ISSR (inter-simple sequence repeat) markers can shed light on the evolutionary origin of E. pallida.

Key words: allopolyploidy, allozymes, Echinacea pallida, ISSR, pale purple coneflower