HOOPER, ELISABETH A.* AND POLLY HIGGINS. Department of Biology, Truman State University, Kirksville, MO 63501. - A preliminary investigation into the origin of the Pale Purple Coneflower, Echinacea pallida (Asteraceae), using allozyme and ISSR markers.
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