TESTS OF THE GENETIC BASES OF CHARACTER DIFFERENCES BETWEEN HELENIUM-VIRGINICUM AND H-AUTUMNALE (ASTERACEAE) USING COMMON GARDENS AND TRANSPLANT STUDIES

TO determine whether Helenium virginicum is distinct from H. autumnale, we compared morphological and ecological characters of more than 450 seed-grown plants from six populations of H. virginicum and nine populations of H. autumnale in common and transplant gardens. Populations compared were selected after we surveyed more than 1,000 herbarium sheets from eight herbaria in search of populations of H. autumnale most similar to H. virginicum, as well as populations representing the range of morphological variation of H. autumnale in the eastern U.S. Six narrow-leaved H. autumnale populations from New Jersey, Missouri, and Ontario, Canada, were chosen because of similarity to H. virginicum, while three populations of H. autumnale from Vermont and Virginia represented the broad-leaved form. Transplant gardens were H. autumnale habitats and H. virginicum habitats. We found H. virginicum to be distinct from both New Jersey narrow-leaved and broad-leaved H. autumnale in 14 of 15 morphological characters as well as in survival in transplant gardens. Twelve of 15 morphological characters, plus survival in transplant gardens, distinguished H. virginicum from Canadian narrow-leaved H. autumnale. Future genetic and evolutionary studies are needed to clarify the relationship between H. virginicum and the Missouri population, which differed from H. virginicum in only three of 15 morphological characters and survived better in H. virginicum habitats than in H. autumnale habitats. Common-garden grown hybrids between H. virginicum and H. autumnale were easily recognizable by morphology and had reduced pollen fertility. Similar hybrids have not been observed in the held.