Helianthus anomalus is a well characterized diploid hybrid species occurring in several geographically isolated sand dune habitats in Utah and Arizona. The parental species H. annuus and H. petiolaris can be found in the same area but show different habitat preferences. We are interested in the genetic bases of adaptations that allow the hybrid to occupy habitats that are not suitable to the parental species. Novel characteristics can slowly evolve through mutational divergence or might be an immediate byproduct of hybridization. One possible mechanism that generates novel characteristics directly through hybridization is transgressive segregation, which QTL studies explain through complementary gene action. We have identified several morphological and ecophysiological characters that are unique to the hybrid species. We have compared artificial and natural hybrids to determine whether characters that are unique to the natural hybrid species are present in artificial hybrids.

Key words: Helianthus, hybridization, speciation, sunflowers, transgressive segregation